2021 UPDATE : Best Indoor Generators | Portable Battery Power Stations

In this article we review 5 of the best Indoor Generators for the money. A couple models have been discontinued in 2021 but new models from Goal Zero enter the foray as well as Westinghouse adding a couple small indoor generators to the mix where they had none before. This is becoming a fast growing market as these advanced models provide the best of both worlds — clean “no maintenance” power that you can safely use indoors; not to mention the fact that they’re near-silent.

What a difference a year makes. Currently, I’m updating this article as some models have been discontinued and have been replaced by much better models, with more power and better features, such as MPPT (Maximum power point tracking), which serves to maintain a consistent load under all circumstances. This is just one new feature that many new indoor generators have in 2021 — well, at least the quality models.

If you don’t already know, Indoor generators are also commonly called : Portable Battery Power Stations and they are 100% safe to use indoors. I prefer the name “indoor generators,” as it’s more descriptive and distinguishes what sets them apart from gas generators. Either way, they do provide a much-needed gap in our ever-growing need for portable power, which will never go out of style.

We discuss a wide range of topics about indoor generators that will help you choose the appropriate model for your specific needs, as well as educate you on the various factors and features that are available. We go deep on this topic.

Introduction — Indoor Generators

Indoor generators have numerous advantages over conventional gas-powered machines. A more logical term for these devices is a Portable Battery Power Station because the generator stores power in a battery, or batteries, and then converts the DC battery power into AC power by means of an inverter. This allows us to use the battery power station indoors, there’s virtually no noise and no toxic exhaust gasses from the engine that we normally associate with conventional generators. This review is all about our choice of the top 5 indoor generators available today.

State of The Art : Indoor Generator — ►Goal Zero 1500X (read review)

For many years, I was is in the business of supplying generators for backup power. These ranged from small units for basic home use and camping, all the way up to large-scale industrial and commercial backup power. This included both indoor generators and gas-powered generators. As for indoor generators (portable battery power stations), there is more than one way of keeping the batteries charged: grid power (using a 110V outlet), solar panels (using the sun to charge the batteries), or a hybrid system that can use conventional AC power as well as solar. Some even allow for charging the batteries using your car, which can be great for camping and tailgating, or outdoor parties.

Based on my years of industry experience in the field, I want to share my personal account and explain why I feel indoor generators are the best way to go. I found that, when presented with the facts, most people agree with me on this. When I was in this business, I supplied way more indoor generators than gas-powered models, even though most people initially felt that gas-powered generators were the only viable option.

Because this review is about small indoor generators, used for home and camping, the example of what I did in my own home is a perfect way explain to you why these devices are so fantastic. I have a relatively small battery power station, it provides 750W continuous running power, with a peak (surge) output of 1,200W, and is connected to 2 X 105AH deep cycle batteries. This supplies uninterrupted, pure sine wave power to all my electronic equipment and household lighting.

New for 2021 ►150W run / 300W start — Battery Generator : iGen300s

This point has to be emphasized: Pure Sine Wave means that the power is completely safe for electronic devices. I did a lot of research into inverter power, back in the day. I’ve concluded that keeping your computers, TVs, and similar electronic equipment permanently plugged into an inverter power supply offers the best protection. The grid power fluctuates and occasionally surges to dangerous levels. Using a local power supply from an inverter, with computerized power management, means that your electronic equipment will never be harmed by “dirty” current from the grid power supply.

The second thing that has to be pointed out is the benefit of an Uninterrupted Power Supply (ups). When I installed my indoor generator, I made this a semi-permanent installation. The portable battery power station remains plugged into a socket 24/7/365. Leading from the outlets on the indoor generator, I installed wiring to two plug sockets. One supplies my computer, router, and other office equipment, as well as chargers for cell phones and other portable devices. I installed a second socket for my TV, satellite receiver, and surround sound system.

Occasionally, I’ve used a small (400W) space heater when it’s been particularly cold. Though, the heater tends to consume quite a bit of battery power. I also connected my light circuits in the home to the indoor generator. This means that, when the power fails unexpectedly, my lights, computers, TV, etc. don’t shut down. They keep functioning as if the grid power was still working. There’s no need to go outside and switch the generator on, then wait for everything to reboot.

VIDEO | A Closer Look at : Goal Zero Yeti 3000X / Tech

These are the primary reasons why an indoor generator is probably the best solution for a home backup power supply. There are other advantages and a few disadvantages too. Portable indoor generators, with built-in batteries, and the option for solar panels to charge the batteries, can be great for camping, tailgating, and RVs.

After reviewing the top 5 indoor generators, I’ll provide a more detailed guide to buying and using indoor generators. I’ll point out the pros and cons of indoor generators vs gas-powered generators, as well as a whole lot of technical information on inverters, batteries, and solar panels. I think there’s a lot of valuable information to be gained from this article and I can certainly shed some light on the topic.

Top Indoor Generators — Reviews

Of the top 5 indoor generators that we’ve selected for this review, some are more suited for portability, making them great for camping, RV use, even jobsites. The larger models can provide more power but are less portable. These indoor generators can be fantastic for home backup power, especially if permanently (or semi-permanently) installed. It’s possible to connect several power outlets and lights to an indoor generator, then still be able to unplug it and use the generator for other purposes.

Jackery Explorer 440 / DISCONTINUED — Out with the old, & in with the…

💡 Welcome the NEW — Jackery Explorer 500

Buy on Amazon

— Read Customer Reviews —

Well, when this article was first written we selected the Jackery Explorer 440 as one of the top picks for a power station but they have since discontinued the generator. But, the good news for consumers is that they’ve updated their line-up and improved the design. Now, in 2021, I recommend the Jackery Explorer 500 or the Explorer 1000 power station instead of the Explorer 440. Consider it progress — and you get better value for your money; not to mention more power.

Features :

• Lithium battery : 518Wh/144,400mAh battery capacity
• 500W Rated / 1000W Start — Pure sine wave AC port.
• Weight : 13.32 lbs with an easy-carry handle.
• Includes 3x USB ports, AC outlet, 12V car output.
• Optimized solar charging with MPPT technology
• LCD screen with charge/discharge data and battery life status.
• 4 Ways of recharging :
  • Solar panel with 62W input wattage max
  • Wall outlet with 80W input wattage max
  • Car outlet with 42W input wattage max
  • Generator with 80W input wattage max

Versatile Portable Power Station :

One the best Portable Battery Power Stations for light-duty power needs, such as : camping, hunting, fishing, backyard barbecue, picnics, music festivals and more. Can run a TV for about 7.5 hours. This isn’t the best choice if you want an indoor generator for power outages or emergencies but if you need a little power to recharge your laptop or smartphone this is a good choice. Also, if you need power for you CPAP machine, this will keep it powered for 24 to 40 hours.

►Read our indepth review of the Jackery 500 to learn all the details. Get the facts then make a decision.

The now discontinued Explorer 440 | Compare to the 500 model

Features: (440 Explorer)

• 440-Watt  Lithium battery, portable power station
• Easy-carry handle
• Fully equipped to connect and charge your devices, Includes :
  • AC pure sine wave inverter (110V, 60Hz 300W)
  • Three — USB-A ports 5V 2.1A (21W Max)
  • Two — DC 12V port (12V 10A)
  • Car port (12V 10A)
• Built-in LED flashlight provides convenience when you need it most
• Info LCD display screen provides charge and discharge status and reports power use
• 2-Year Jackery Warranty, including battery
• An optional 100W solar panel provides sustainable power resource anywhere
• Peak Capacity: 440Wh (21.6V, 20.4Ah) 122,400 mAh / 3.6V
• Cell Chemistry: Li-ion NMC
• Lifecycles: ≥500 cycles to 80%
• Shelf-life: Charge every 3-6 Months
• Management System: BMS, Over Voltage Protection, Short Circuit Protection
• Charge Methods: AC Wall Outlet, Solar Panel (optional)
• Full Recharge Time :
  • 8 Hours (AC)
  • 10 Hours (Optional 100W solar panel with Full Sun)
• Weight : 12.6 lbs (5.7 kg)
• Dimensions : 11.8″ L x 9.5″ W x 7.6″ D : (30 x 24 x 19 cm)

Overview | Original Review for the Explorer 440

The Jackery Explorer 440, is probably my number one choice for a portable camping battery power station. I say this because it is contained in one, small, easily portable unit. The use of lithium ion batteries, as opposed to heavier lead acid batteries, means a good length of usable battery time without too much additional weight. The inclusion of a solar charging port is another important consideration for off-grid use, like camping and fishing trips.

Outlets, Ports and Controls

Power is somewhat limited, but that’s what makes this a such a small, relatively lightweight indoor generator. The Jackery Explorer uses an advanced pure sine wave inverter, making it perfectly safe for all electronic equipment, even critical medical equipment, like a CPAP (Continuous Positive Airway Pressure) machine for assisted breathing. Continuous power output is rated at 300W, with a maximum output current of 500W. Though the peak, or surge power is only rated at 440W. At best, the Explorer 440 can supply power for a portable camping refrigerator (mini-fridge). Though I think it is best suited for electronic devices, charging batteries, supplying power for a TV, computer, and lighting. Of course, it can also be a lifesaver if you depend on electrically powered medical equipment.

The Jackery Explorer 440 measures only 11.8” X 9.5” X 7.6” and weighs a mere 12.6 pounds. A comfortable carrying handle means you can take the nifty little Jackery with you, anywhere you go. I really like the built-in LED flashlight that is always ready for emergency lighting. Dual charging options are another great benefit. You can plug the Explorer into a 110V AC socket, and the battery will reach full charge within about 8-hours. Alternatively, you can purchase the optional 100W solar panel and, in good sunlight, it will take approximately 10-hours to charge the battery.

The Explorer is capable of supplying “through charge”, this means that you can use it while charging the battery. Though power to the 110V outlet socket will be limited whilst charging the battery. Using the Jackery Explorer, whilst charging the battery, will be fine for a laptop, or a few LED lights, but you won’t have the full 440W peak power available. The charger only supplies a limited amperage, and this needs to supply output power as well charge the battery.

In terms of user-friendly design, I commend the guys at Jackery. It has a single on/off switch and an LCD display for the information you need. It will display the power usage at the outputs and provide system information for the battery charge status. There are 3 X 5V USB outlets which provide energy efficient charging for all types of USB devices. A car cigarette lighter style 12V DC (10A) outlet allows you to charge or run 12V equipment.

The 122400mAH (440WH) lithium ion battery has the advantage of being lightweight with a great power supply time. Because the USB outlets are not dependent on the inverter, efficiency at these outlets are optimized. You can charge a cell phone 31 times or more; tablets – 25 times; cameras – 50 times; or drones 5 times. A USB fan can run for about 40 hours or more. The 110V AC outlet will power a mini fridge for around 6-hours, or an LCD (32”) TV for 10-hours or more. The built-in lithium ion battery is good for approximately 500 cycles, up to 80% of the maximum discharge capacity. This is provided you use the battery correctly and charge it at least every 3-months.

Although the Jackery Explorer 440 is limited in the power that it can supply, it may be one of the top choices for both camping and basic emergency backup power for the home. Even if you’re using a portable generator for your RV or home, the Explorer can be an invaluable supplementary power supply. At night, you may not want to burn through gas unnecessarily, or disturb the nighttime silence with a noisy generator. During the day, you can run the generator for the high-watt equipment and charge the Explorer. When the sun sets, switch the generator off to save gas and enjoy some peace and quiet, while the Jackery provides the power you need for lighting, watching TV, using your laptop, and charge your USB devices.

At around $500, the Jackery Explorer may seem a little expensive for an indoor generator that only supplies a peak output of 440W. Though, in terms of portability and exceptional quality, I feel it’s worth it. The Fact that Honda (one of the top names in the portable generator business) has put their brand to the Jackery, selling it as the Honda indoor generator, says a lot about this product’s reliability and durability. A great 2-year warranty goes even further to instill confidence in this product. For tailgating, camping, medical emergency power, and basic home backup, this is a top-notch battery indoor generator.

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EGO POWER+ Nexus PST3042 | Indoor Generator

Equivalent power to a 3000 watt (peak) generator — but it’s silent, no fumes, can be used indoors, no maintenance and overall an excellent solution if you need an indoor portable generator.

Buy on Amazon

Features :

• 3000 Watt Starting / 2000 Watt Running
• 3x 120-Volt A/C outlets
• 4x USB Ports
• Bright LED Display Shows Run Time
• Battery Powered Alternative to Gas Generators
• Quiet Clean Power for Indoor and Outdoor Use
• 4 Port Battery Charger (when plugged in).
• Weather-Resistant Construction
• 3000-Watt peak 2000-Watt continuous
• Rugged aluminum handles
• Includes : 2 EGO POWER+ ARC lithium batteries (7.5 Ah)
• Works with 1, 2, 3 or 4 EGO batteries of any size, in any combination
• Clean, quiet, battery-powered generator.
• Same power as a 3000W gas generator.
• Pure sine wave inverter that runs cooler and more efficient than traditional generator.
• Safe to use indoors and outdoors
• Perfect for camping, tailgating, on the jobsite, or during power outages
• Power a refrigerator, microwave, Wi-Fi router, and essentials during power outages.
• Weight (Without Battery Pack) 30.2 lb (13.7kg)
• Operation Temperature Range : 5°F – 104°F (-15°C – 40°C)
• Storage Temperature Range :-4°F – 158°F (-20°C – -70°C)
• Charge up to 4 EGO batteries
• Control your Nexus from anywhere with EGO connect app
• Weather resistant construction

✓ View or download the MANUAL for the Ego Power+ Nexus.

Overview

The New Ego POWER+ Nexus (PST3042) is a much more powerful indoor generator than the earlier generation Nexus Escape. Continuous power is up from 150W to 2000W running power, with a surge capacity of 3000W. This is good news for RV owners and people who want a home backup battery power station, capable of running a refrigerator or microwave. Though I’m not too sure if the battery system is the best. It uses the tried and tested Ego 56V lithium ion batteries, which are excellent. But you have limited ampere-hours, even when using the maximum four batteries that the Power+ Nexus can accommodate. For an indoor generator with kind of power output, I would prefer the option of using extra deep cycle batteries for longer runtimes.

VIDEO | A Closer Look at the EGO POWER+ Nexus

Best Battery Inverter - EGO Nexus Power Station Review - 2000W

This is certainly a great product. It is water resistant which makes it great for camping. There is no IP certification for waterproofing, but everything is sealed to protect the Nexus from moisture. I wouldn’t recommend using the Nexus in rain or snow, but it can withstand a fair amount of moisture, making it suitable for outdoor use. The design is fantastic, chunky handles all around, make for easy carrying and provide excellent impact resistance. Without the batteries, it weighs 30.2 pounds. Considering that this is a very powerful unit, the weight is astounding. Even with the batteries, it won’t be much heavier. Lithium ion batteries are not particularly heavy. As far being a high-power portable battery power station, the Ego Power+ Nexus scores top marks.

Now for the not so good news. Nexus is a little hesitant to provide much information on the batteries and how they work. This is understandable, since it is not the greatest selling point. I did the math, and the numbers aren’t all that favorable when looking at battery standby time. The Nexus can accommodate a maximum 4x EGO 56V lithium ion batteries. The top-rated batteries in this series provide 7.5AH. Using four 7.5AH batteries can be fine for a TV, laptop, LED lights and similar low-watt equipment. But the Nexus is rated for 2000W continuous power. If you’re using 4 X 7.5AH 56V batteries, you have a total running time of 1680 Watt-hours. At full capacity (2000W), the Nexus will provide power for less than an hour before the batteries need to charge. To aggravate the situation, you cannot use the generator whilst the batteries are being charged.

I suppose it is unlikely that you’ll be using the full 2000W running capacity continuously at any given time. So, I did a few real-world calculations, for the type of situation where one would be using the Nexus in everyday use. I considered a mid-sized refrigerator cycling on and off on a moderate day and allowed for some other equipment being used simultaneously. The combined load of the additional appliances being equivalent to about 5 (10W) LED lights, a desktop computer, and a 42” LCD TV. At best, I came up with around 3 – 4 hours before the batteries need recharging. Not ideal, since you’ll have to disconnect the outlet power and wait several hours before all the batteries are recharged and ready for use. Ego don’t give exact charging times, other than to say: “leave overnight to charge”. I would think anything from 6 – 8 hours for 4 X 7.5 AH batteries.

Now, this may not be all bad news if you already own EGO battery-powered tools that use their 56V batteries. If this is the case, you’ll probably have quite a few batteries and an additional charger. If you have 8 X 56V 7.5AH Ego batteries, you should get up to about 8-hours (possibly more) using the type of load I used in the above example. If you’re planning a week-long camping trip, the amount of batteries that you’ll need will be exorbitant, and the EGO does not allow for solar charging. Given all of this, I’d say that the Nexus is great for fairly comprehensive backup power at home during an outage of not more than 8 – 12 hours, or a day trip.

If you want to use the Nexus for camping trips or longer home use, I’d suggest buying a small gas generator which doesn’t cost much. The battery charger requires less than 2A current, so you can use the smallest, cheapest generator to charge the batteries when needed. The generator will never work very hard, as the charging load is so little, so you really won’t need a top-rated machine for this purpose. The Nexus can be used for your actual load, providing quiet clean power for all your needs.

I should also point out that the power output is electronically controlled in relation to the amount of batteries that you use. If you’re only using one battery, the Nexus will automatically restrict the output load to 600W. It then increases to 1200W or 2000W, as you add more batteries.

Other than the battery conundrum, I cannot fault the Nexus. It is a high-quality product, using a state-of-the-art, true sine wave inverter. Electronic controls are of the highest order. An LCD display gives you accurate real time information on load and battery status. Each of the four batteries are indicated separately with pretty cool graphics. I particularly like the countdown timer. It will calculate your load vs battery charge status when discharging the batteries, estimating your remaining runtime. You will see the time remaining on the LCD screen. When charging the batteries, it also provides a timer, indicating how long before the batteries reach full charge.

VIDEO | A Quick Overview of the EGO Nexus

Introducing: EGO POWER+ Nexus Power Station

The Nexus has overheating and overloading shut-off, with warnings to let you know what’s happening. You also have the convenience of Blue Tooth and WiFi connectivity, allowing you to use a smart device to control and monitor the Nexus, by means of a downloadable app.  Power outlets consist of 3 X 120V AC sockets and 4 X 5V (2.1A) USB ports.

While I have a bit of an issue with the battery limitations, I cannot deny that the Ego POWER+ Nexus 2000W/3000W indoor generator is one of top models. It has real power, that can provide for most of your emergency household or RV needs. Design and build-quality are tops. A testament to this, has to be the remarkable 5-year warranty on the indoor generator and 3-years for the batteries.

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NEW Updated Series : Goal Zero “X”

►YETI 3000X : And the “X” Series in General (Read our guide to the X Series)

Features : YETI 3000X

• Power a wide range of devices with seven different port options including fast-charging 60W USB-C Power Delivery, multiple USB-A ports, regulated 12V, and two 120V AC ports.
• Integrated MPPT charge controller ensures you’re getting the most efficient solar charge possible.
• 2000W AC (3500W Surge) inverter allows you to run power-hungry devices and appliances with confidence. Our new industry-leading inverter can handle surges from power tools, medical devices, and home appliances, including full-size refrigerators.
• Yeti App 3.0. Features remote control of power in/out, real-time power consumption notifications, and charging profiles to optimize your battery life.
• Examples : Hours of Runtime
  • Light-a-Life 350 (4.5 Wh): 674 hours
  • Light Bulb (11 Wh): 276 hours
  • CPAP (65 Wh): 47 hours
  • TV (42″ LED) (100 Wh): 31 hours
  • Pellet Grill (60 Wh): 51 hours
  • Microwave (1000 Wh): 3 hours
  • Portable Fridge (25 Wh): 122 hours
  • Mini Fridge (35 Wh): 87 hours
  • Full Size Refrigerator (55 Wh): 55 hours
  • Circular Saw (13 Amp) (1500 Wh): 2 hours

OLD Goal Zero Models —-

Goal Zero Yeti 400 (LITHIUM) / Goal Zero Yeti 3000

Goal Zero Yeti indoor generators provide the full package with complete convenience and versatility. The smaller Goal Zero Yeti 400 (300W) generator can compare very favorably to the Jackery Explorer (at the top of the review). The Goal Zero Yeti 3000 can be compared to the Power+ Nexus (reviewed above). It has the same output as the Nexus (3000W), but with the twice the battery time, and an option for solar charging. It is, however, much heavier than the Nexus, making it a less favorable option as far as portability is concerned.

Goal Zero — Yeti 400 // Yeti 400 LITHIUM

Indoor Generators that can be connected to solar panels for recharging.

Note : There are two different versions of the Yeti 400 — The Yeti 400 and the Yeti 400 LITHIUM. See the features below for the differences between each model. It can be confusing if you are unaware of the two versions.

Comparison Chart : Goal Zero Yeti 400 vs Yeti 400 LITHIUM

✓ NOTE : Either of these Yeti 400 indoor generators can : Recharge mini-Fridge up to 7 hrs., 32″ LCD TV up to 3 hrs., recharge your smartphone up to 20x (depending on battery)

Feature Comparison  — Yeti 400 vs Yeti 400 LITHIUM :

• Quiet, lightweight, indoor generator.
• BATTERY :
  • Yeti 400 Regular :
    • Replaceable sealed lead-acid AGM battery
    • Cell Type: AGM Lead-Acid
    • Peak Capacity: 396Wh (12V, 33Ah)
    • Lifecycles: hundreds of cycles
    • Shelf-Life: Keep plugged in, or charge every 3-6 months
    • Fuses: none
    • Management System: Charging and low-battery protection
  • Yeti 400 Lithium :
    • Replaceable lithium battery
    • Cell Chemistry: Li-ion NMC
    • Peak Capacity: 428Wh (10.8V, 39.6Ah)
    • Lifecycles: 500 cycles to 80% (discharge rate: 1C, full charge/discharge, Temp 25C)
    • Shelf-life: Keep plugged in, or charge every 3-6 months
    • Management system: PWM (pulse-width modulation) charge controller, low battery protection
• PORTS :
  • Yeti 400 Regular :
    • USB port (output): 5V, up to 2.1A (10W max) regulated
    • 6mm port (output, 6mm, green, hexagon): 12V, up to 10A (120W max)
    • 12V car port (output): 12V, up to 10A (120W max)
    • AC inverter (output, 60Hz, pure sine wave): 110V, 2.6A (300W continuous, 600W surge max)
    • Power Pole Chaining Port: 12V, up to 33A (400W max)
    • Charging Port (input, 8mm, blue, circle): 14-29V, up to 10A (120W max)
  • Yeti 400 Lithium :
    • USB port (output): 5V, up to 2.4A (12W max), regulated
    • 6mm port (output, 6mm): 12V, up to 10A (120W max)
    • 12V car port (output): 12V, up to 10A (120W max)
    • AC inverter (output, pure sine wave): 120VAC 60Hz, 2.5A (300W continuous, 1200W surge max)
    • Charging port (input, 8mm): 14-22V, up to 10A (120W max)
• GENERAL :
  • Yeti 400 Regular :
    • Chainable: Yes
    • Weight: 29 lbs (13.2 kg)
    • Dimensions: 10.25″ x 8″ x 8″ (26 x 20.3 x 20.3 cm)
    • Operating Usage Temp: 32-104 °F (0-40°C)
    • Certs: CE, FCC, ROHS
    • Warranty: 6 months
  • Yeti 400 Lithium :
    • Chainable: No
    • Weight: 16.3 lbs (7.4 kg)
    • Dimensions: 7.5″ x 11.2″ x 7.0″ (19.0 x 28.6 x 17.7 cm)
    • Operating Usage Temp: 32-104°F (0-40°C)
    • Warranty: 12 Months
• Solar Panels :
  • Yeti 400 Regular / Yeti 400 Lithium
  • Goal Zero : Boulder 50, 100 & 200 (4 to 8 hr. recharge)
  • Goal Zero : Nomad 100  (6.5-16 hr. recharge time)

Manuals :

• ✓ View or download the MANUAL for the Yeti 400 LITHIUM.
• ✓ View or download the MANUAL for the Yeti 400.

Overview (Yeti 400) :

In terms of technical specifications, there is no real difference between the Goal Zero Yeti 400 and the Jackery Explorer 440. This model provides almost the same output power and the battery time is about the same too. This makes it suitable for laptops, LED lights, charging USB devices, or a mini fridge. When I say the power output for the two indoor generators is almost the same, the difference should be pointed out. The Yeti has the same continuous power output as the Jackery Explorer (300W). But the peak (starting current) is almost 3-times higher than the Explorer. This could make the Yeti more capable when it comes to using a small camping refrigerator with a high startup load.

While I prefer the design of the Jackery, the Yeti 400 isn’t all that different in terms of dimensions and weight. The Yeti is a little heavier, at 16.3 pounds (vs 12.6 pounds for the Explorer). The Yeti has a boxier shape, but isn’t much larger, measuring 7.5” X 11.25” X 7”. It’s superbly portable with a great fold down handle.

The Yeti 400 has the outlets to match: 2 X 120V (2.5A) AC outlets and 3 X 5V (2.4A) USB ports. It also has two 12V 10A charging ports, one being a 6mm (¼”) port and the other, a regular car cigarette lighter type outlet.  The 39.6AH (10.8V) lithium ion battery provides just about the same number of watt-hours, when compared to its rival, the Jackery Explorer 440. You can expect similar performance: cell phone charging – 31 times or more; tablets – 25 times; cameras – 50 times; or drones – 5 times; mini-fridge ±6-hours; 32” LCD TV 10-hours+.

Like the Jackery, this is a rugged, portable indoor generator that is equally at home in the great outdoors. It has the same advantage of a comprehensive LCD display, and the option for solar or AC battery charging, with similar charging times. The Goal Zero Yeti 400 has the additional advantage of a 12V charging port, making it possible to charge the generator using your car. Though it will take 4-7 hours to charge the Yeti in this way. It would be a good idea to start and run your car engine a few times during this period to prevent your car battery from fully discharging.

VIDEO OVERVIEW | Goal Zero Yeti 400 LITHIUM

Depending on where you look, you could end up paying around 100 bucks more for the Yeti, compared to the Jackery Explorer. Since these two indoor generators have almost identical technical specifications, it could be hard to justify the higher price. The only notable difference that I can find, is the 12V car charging option. Of course, this can be quite a benefit. You can charge the Yeti 400, when camping or tailgating, without the additional expense of a solar panel.

⚡️ Even More Power : Goal Zero YETI 6000X

The 3000X can keep your home comfortable during a power outage, and you can safely it indoors. Technology has been advancing at a fast pace for indoor generators over the past year or so. The future looks bright. The Tesla Powerwall is what the future of home power will look like. You can thank Elon Musk for jump-starting battery power in the 21st century.

Just to share one tidbit of knowledge about the Yeti 3000X : It Can run a full size fridge for over 50 hours (2 days straight) so your food doesn’t spoil when the power goes out. Trust me, food spoilage is a massive problem when the power goes out.

An excellent alternative to gas-powered inverter generators. Produces 1500W of running power and a 3000W of starting power. Clean, no fumes, no maintenance. Run it indoors. Ideal for emergencies and power outages. Included wheels make it easy to move around.

Read our review of the updated X-Series models for 2021 : YETI 3000X

Goal Zero — Yeti 3000 (Discontinued)

Features (Yeti 3000 LITHIUM): Older model review

• Patented AC and 60W USB-C Power Delivery Ports
• 10 ports available with high surge capacities for greater compatibility with more power-hungry devices, and the latest in USB-C power delivery capable of charging larger USB devices like laptops.
• WiFi Connected Power Station : Connect a mobile app enabled Yeti through your WiFi router and control it remotely using the new Goal Zero Yeti App. Turn ports on or off, check battery levels, even update the Yeti’s firmware with your chosen device. App can be downloaded via the Apple Store or Google Play Store.
• MPPT Pre-Installed : Solar charging optimization module that functions as a maximum power point tracker (MPPT), resulting in up to 40% faster charge times, especially from solar panels.
• Includes Wheels and Telescoping Handle : Mobility kit comes pre-installed and can easily be removed when needed.
• Ultra-safe Lithium Battery : Quality lithium cells, known for stability, monitored by a state-of-the-art battery management system that prevents over-charge, over-current, and short circuiting. The battery pack is enclosed in a water-tight enclosure that seals it from the elements and allows for a user-replaceable system, lending to the overall longevity of the product.
• RECHARGE :
  • Recharge from the sun by connecting a compatible solar panel. Charge time is dependent on the size of the solar panel. The Boulder 200 Briefcase will fully recharge the Yeti 3000 Lithium in about 18-36 hours.
  • Plug it into the wall. Fully recharges in 10 hours using the [Yeti Fast Charge 25 Amp Power Supply and 25 hours using the two included wall chargers.
  • The Goal Zero Yeti 3000 Lithium can be charged by plugging into your 12V adapter using the Goal Zero Yeti Lithium 12V Car Charging Cable.
    • NOTE: Do not attempt to charge your Yeti Lithium from a 12V source using a regular charging cable. Doing so may cause damage to the unit.
• APP :
  • Redefine power at the push of a button with the smart, easy-to-use Goal Zero Yeti App. Sync your Yeti directly with the Yeti App using Direct Connect or establish a connection via an available WiFi network.
  • Check battery level, power in and out, even turn ports on and off, all from the palm of your hand.
  • Over the air firmware updates keep your Yeti performing at its best and are easily managed within the Goal Zero Yeti App.
  • Connect multiple Yetis to a single device, or multiple devices to a single Yeti.
• PORTS :
  • USB A port (output): 5V, up to 2.4A (12W max), regulated
  • USB C port (output): 5V, up to 3.0A (15W max), regulated
  • USB PD port (output): 5V, 12V, 20V up to 3.0A (60W max)
  • 6mm port (output, 6mm): 12V, up to 10A (120W max)
  • 12V car port (output): 12V, up to 10A (120W max)
  • 12V Power Pole port (output): 12V, up to 20A (240W max)
  • 120V AC Inverter: 120VAC 60Hz, 12.5A (1500W, 3000W surge)
    (output, pure sine wave)
  • Charging port (input, 8mm): 14-22V, up to 10A (120W max)
  • Power Pole charging port (input): 14-22V, up to 30A (360W max)
  • Expansion Module port Covered port under the lid. To be used with Goal Zero expansion modules only
• GENERAL :
  • Weight (Yeti & MPPT charger): 68.6 lbs (31.1 kg)
  • Weight (cart only): 8.9 lbs (4 kg)
  • Dimensions (Yeti only): 10.1″ x 15.3″ x 13.1″ (25.7 x 38.9 x 33.3 cm)
• BATTERY : Cell chemistry: Li-ion NMC. Pack capacity: 3075Wh (10.95V, 280.8Ah)

✓ View or download the MANUAL for the Yeti 3000 LITHIUM.

Overview

I am suitably impressed with the Goal Zero Yeti 3000. I’ve compared it to the Ego Power+ Nexus, though I feel the Yeti is the more practical of the two. Before I go onto the advantages that the Yeti 3000 has over its 3000W counterpart, I should point out the major disadvantage. While both the Yeti 3000 and Power+ Nexus have the same peak power (3000W), the Nexus has 500 watts less continuous power. At 1500W (vs 2000W for the Nexus), the Yeti cannot supply the same constant load. The power difference is a full 25%, which can make a big difference in your use of the generator.

With 1500W continuous power and a 3000W peak, the Yeti 3000 will run a regular refrigerator, along with other basics, like TVs, computers and lights. The limitation will come in when using two high-powered appliances at the same time. If you want to use your microwave, you’ll probably need to disconnect the refrigerator first. The other slight inconvenience, with regards to the Yeti 3000 vs Ego Power+ Nexus, is the weight of 68.6-pounds. Though this extra weight is unavoidable, as this one has a considerably larger battery and a built-in solar charger. Both of these are of great benefit, which makes the extra weight a necessary evil. The Yeti 3000 is supplied with a great transportation cart, so it is still portable. The cart has large wheels, capable of moving over pretty rough terrain, and a telescopic handle.

Now for the long list of pros that make the Goal Zero Yeti 3000, in my opinion, one of the top indoor generators. First of all, the Yeti 3000 has an amazing lithium ion (10.9V) 280.8 AH battery, providing a whopping 3075 watt-hours. This battery provides over 2-hours, at maximum continuous output. I reckon, under normal usage, you should get around 6 – 8 hours from the internal battery. The really remarkable part of this generator is the ingenious Yeti Expansion Module system. This allows you to connect additional batteries of a different type. So, you can chain extra batteries and they don’t have to be Yeti lithium ion batteries, you can use regular lead acid batteries. I think that this is the only system of its kind. In addition to this, the Yeti 3000 has multiple charging methods, with every type of input port there is.

VIDEO | A Closer Look : Goal Zero Yeti Generators

The Yeti 3000 indoor generator is supplied with 2 X 5A 110V AC chargers, this will charge the internal battery in about 25-hours. They also supply an optional 25A high-power charger that will reduce the AC charging time to around 8-hours. You will need to buy this charger separately. The Yeti has a built-in MPPT (Maximum Power Point Tracking) solar charger with 2 X 14 – 22 Volt solar inputs. The 10A (8mm) input allows you to connect a Boulder 100 solar panel, with a charging time of 41 – 120 hours, depending on the available sunlight. An additional Power Pole solar charging point can handle a solar charge of 30A (up to 3 X 100W solar panels), which will reduce your solar charging time to 14 – 40 hours. The handy Boulder Briefcase is a wonderfully portable 200W solar panel kit that is easy to set up and will charge the Yeti 3000 to full within 20 – 60 hours. You also have the option to use one of two (10A or 20A) 12V car charging ports.

Output ports for the Yeti 3000 are equally impressive. Not least of which has to be the full array of USB ports with enough amperage to charge a laptop. It has the common USB A (5V, 2.4A) port that is used for phones and tablets up to 12W. The USB C port provides 5V up to 3A, with a maximum rating of 15-watts. Then there’s the less common USB PD port, that supplies 3A at either 5V, 12V, or 20V, taking the charge capacity up to a maximum of 60W, suitable for most laptops. The array of 12V DC outlets is more than most. A regular 10A cigarette lighter style car outlet is provided, along with a 6MM (¼”) 10A 12V output and a 12V Power Pole output that can supply 20A (up to 120W).

VIDEO | A Closer Look : Yeti APP

The dual 120V conventional household outlets each provide 12.5A pure sine wave, inverter AC power. The LCD screen provides all the system information in an easy to follow format. You can see, at glance, how much power you’re using, the battery charge level, and remaining run time. The Yeti 3000 has a very useful Wi Fi enabled phone app with a lot of additional functions and information.

The Goal Zero Yeti 3000 must be one of the most accomplished battery-powered indoor generators around. It has the output to compete with gas generators and a built-in battery to provide decent backup time. The option to chain additional batteries, multiple charging ports, and the most comprehensive array of power outlets, most certainly places the Yeti 3000 in a league of its own. Okay, it’s a bit on the heavy side, and somewhat bulky, but this is to be expected when you look at all that has been packed inside this machine. I can’t help but be totally impressed with this marvel of technology. It has everything I’d want in a portable battery generator for both home and camping applications.

Visit the Goal Zero site to learn more about their Yeti power stations, solar panels and other well-made products.

Sun Joe SJ1440SG – Discontinued

Indoor or outdoor generator. 1440 running watts. 1800 starting watts. Released in 2019. Sadly, another example of a great product that didn’t last very long in the marketplace.

Features:

• Compatible with the Sun Joe folding panels attachment SJ1440SP (no longer available)
• Fuel-free portable power for small, household electronics, jump-starting engines, RV trips, camping, and power tools
• Charges from 120 Voltage wall outlet or optional solar panel
• 4 in. LCD displays system information battery status
• Internal sealed lead acid (SLA) battery is non-toxic, fuel and fume-free, and safe for indoor outdoor use
• Continuous output power: 1440 Watt
• Equipped with 2 car auxiliary outlets, 2 USB ports and 2 plug outlets
• AC charge time max: 24 hours
• Solar panel charge time max: 60 hours
• Made from plastic and metal
• Warranty: 2 years limited
• No assembly required
• Weight  : 107 lbs
• Dimensions (L x W x H) : 21.65 x 17.75 x 25.60 Inches

✓ View or download the MANUAL for the Sun Joe SJ1440SG.

Overview

At around a third of the price, compared to the Yeti 3000W, some may find the Sun Joe 1440W (SJ1440SG) indoor generator to be an irresistible bargain. Sun Joe is a cheaper brand and some of the plastic components don’t appear to match the Goal Zero build quality. None the less, the Sun Joe is a reasonably rugged indoor generator, capable of withstanding the rigors of camping and site work, albeit not quite as tough as the formidable Yeti or, for that matter, the Ego Power+ Nexus. Since the Sun Joe SJ1440G Provides 1440W continuous power (only 60W less than the Yeti) at a much better price, I’m sure many would be prepared to overlook the minor discrepancies when it comes to cheaper build quality. The Sun Joe is not at all that flimsy. But it is as simple as all that?

Form the outward appearance, one wouldn’t consider the Sun Joe SJ1440SG to be that different when compared to its more expensive rivals. Though, after a detailed examination of the technical specifications, I can see why the Sun Joe is so much cheaper. The most significant difference between the Sun Joe and all the other indoor generators in this review, is the use of a modified sine wave inverter. All the others use a true sine wave inverter. After the review, I’ll explain the technical aspects of inverters, which should help you better understand the difference between square wave, modified sine wave, and true (or pure) sine wave inverters. For now, let’s just say that a modified sine wave inverter is the cheaper option compared to true sine wave inverters.

VIDEO | A Closer Look at the Sun Joe Indoor Generator

The modified sine wave inverter is not as efficient as the true sine wave alternative and, therefore, reduces the time that one gets from a battery. Inverter and exchange efficiency stats for the Sun Joe are rated at 85%.

There are some appliances that don’t function optimally, using a modified sine wave, putting further load on battery. These inverters usually produce an audible humming sound, that can be a little distracting under high loads. Taking all this into account, a modified sine wave is still a step up from the cheapest option, this being a square wave inverter. In the end, you may see a slight pulsing of LED lights, and some electrical equipment may generate extra heat when using a modified sine wave inverter, like the Sun Joe. Not ideal, but you still have power during an electrical outage, or heading off grid. There has to be some sort of compromise at this price.

With the exception of a few cheap plastic components and the less efficient inverter, the Sun Joe compares favorably to the other larger indoor generators in our top 5 review. Though, it doesn’t have a very high peak load. With a surge capacity of 1800W (15A), the Sun Joe is a far cry from the 3000W peak current as seen on the Yeti 3000. This is still enough to provide the in-rush current to start a refrigerator, or microwave, but limits the ability to start more than appliance at a time.

VIDEO | See it connected to the Sun Joe SJ1440SP 60W solar panel

I suppose another reason why the Sun Joe is cheaper, would be the use of a lead acid (deep cycle) battery, the others use lighter, more expensive lithium ion batteries. The only real drawback to this, from a user point of view, would be the extra weight. The Sun Joe weighs a hefty 107 LBS. To manage this weight, it has large built-in wheels and a telescopic handle. The lead acid battery provides a very acceptable 100AH at 12.5V. Though not quite as impressive as the (10.9V) 280.8 AH used to supply the Yeti.

The heavier battery used in the Sun Joe, combined with a less efficient inverter, will provide less than half the runtime when compared to the Yeti. If you’re using the Sun Joe to power a mid-sized refrigerator and few low-watt appliances, I wouldn’t expect more than 3 – 4 hours runtime from the single internal battery. You should be able to power a single TV (or computer), along with a few LED lights and phone charger, in an emergency for about 8-hours.

I see no mention of the ability to chain extra batteries to extend this time. Given the long (24-hour) charge time for the single battery, I seriously doubt whether the charger will handle additional batteries. Though, because the Sun Joe uses a nominal 12V battery, you can haul out your car battery in an emergency, but don’t expect the generator to charge the battery afterward. It has handy jump-starting terminals to start your car if needed, and you can use these same terminals to chain in additional batteries.

Apart from the AC charger, the Sun Joe also has inputs for a solar panel. This is a 20A solar charger and is not of the MPPT variety (another cost cutting measure). The 3-stage charger is not as efficient as the more expensive MPPT chargers with a 5% loss factor. I suppose this isn’t too bad, using a single 60W Sun Joe (10 – 24.5 VDC) solar panel, it will take about 60-hours to charge the internal battery. Though, by my calculations, the 20A solar charger can accommodate four of these panels, which would bring the battery charging time down to a more reasonable 15-hours.

Outlets and user features on the Sun Joe can be compete with any of the top 5 indoor generators in this review. It has 2 X 120V AC outlets, with GFCI protection. The DC outlets include 2 X 12V automotive auxiliary outputs, and 2 X 5V USB outlets. The large LCD screen has a great display for battery level, battery voltage, output watts, charge watts, and time remaining. All the outlets are protected by plastic covers.

Had it not been for the exceptionally good price, the Sun Joe would have no place in this review of the top 5 indoor generators. It doesn’t have the best inverter, it uses a cheaper lead acid battery, and is a little heavier than one would want from a portable battery power station. However, these compromises are perfectly acceptable when you look at the great value that you’re getting for your money. This must be the most affordable indoor generators in its class. Compared to any of the cheaper alternatives, I doubt you’ll be able to match the quality or performance of this product. If you’re not up to spending the extra cash on the real top-rated indoor generators, this would be the one I’d recommend.

ROCKPALS RP300W / Discontinued

Features :

• 300 Running Watts and 600 Surge Watts (max).
• Large Capacity: 280WH (3.7V 75Ah/12V 18.7Ah) high capacity lightweight power pack.
• Numerous powering options including:1*AC output to 300W continuous (600W surge max);5* DC port (16A / 96W max); 2* USB 2.1A and 1*Quick Charge 3.0 usb.
• Pure sine wave better than modified sine wave and clean power like utility supplied electricity.
• Inductive loads like microwaves and motors run faster, quieter and cooler.
• Gas-free source of portable power supply, it runs quiet (The cooling fan on the side of generator will make a slight sound when working), no exhaust fumes.
• An informative display featuring a running time/power time estimator, as well as a power level monitor and an output/input meter.
• Easily powered via the sun powered solar panel or wall outlet.
• On the go power source with lightweight and easy carry handle
• 18 months worry-free warranty and friendly customer service.

What can it power?

280wh(75000mah 3.7v/12v 18750mah) lithium-ion batteries and weighs only 7.3lbs. Powerful enough to charge smartphones 25 times, laptops 4-5 times, 32″ TV 4+ hours, cpap machine 4+ nights(using dc/dc converter), mini-refrigerator 5+ hours, lights or other small appliances and its pure-sine wave inverter provide clean power, just like plugging into the wall at home.

• Powering options :
  • With 120v ac (300w rated / 600w surge) us-standard outlet for your laptop, monitor, tv, air mattress, lamp, fan, router, modem, Christmas lights etc.
  • With 4* 12v dc (48w*3+96w*1) for car powered device under 96w, such as car vacuum, car refrigerator, car air fan, cpap machine etc
  • With 1*24v dc (24v-3a)for connecting 24v appliances.
  • With 4* 5v usb ports (two qc3.0 fast charge) for phones, ipad, gps, mp3, camera, rc helicopter etc.
• Weight : 7.3 lbs.
• Powerful enough to charge smartphones 25 times, laptops 4-5 times, 32″ TVs 4+ hours, CPAP machine 4+ nights (using DC/DC converter), mini-refrigerator 5+ hours, lights or other small appliances.
• Easily rechargeable via the sun or wall:
  • Can be recharged from the sun with any compatible 50w or 100w solar panel (sold separately).
  • Fully charged in 8 hours by being plugged into the wall outlet.
• Pure sine wave inverter: better than modified sine wave and clean power like utility supplied electricity.
• Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, tv, fax and answering machines.
• Quiet
• Ports : DC Output: 3 x DC Output Ports (12V/4Al),1 x DC output 24V/3A
  USB Output: 2 x QC 3.0 USB, 2 x USB Ports (5V/3.1A)
  1 x Cigarette lighter, 2 x Flashing Lights for Emergency,1 x Led Display 
• Includes : Rockpals portable generator (280wh portable generator), ac adapter, car charger cable, mc4 adapter, user guide, our worry-free 18-month warranty and friendly customer service.
• For optimal use with cpap:
  • Rockpals rp250w power station has two ways to power your cpap machine: 110v ac plug or 12v/24v dc plug. We strongly recommend that cpap users use dc converter to work with this power station and turn off or remove the heater/ humidifier, thus it should last at least 4 nights. To buy the dc converter, please consult with your cpap supplier or simply reach us for a guide.

Overview

The Rockpals Portable battery power station is a very affordable option for a small unit to use in your RV or at home. Portability is tops, the Rockpal is wonderfully lightweight and has an easy to use retractable handle. If you were considering the Jackery Explorer 440 or Goal Zero Yeti 400, the Rockpals RP300W might be a more appealing option, as you could end up saving a few dollars and end up with an indoor generator with the same capabilities. I really like the value for money aspect to this product. It has the build quality to compete with any of top indoor generators of this size and an excellent, lightweight, lithium ion battery.

VIDEO | ROCKPALS RP300W Indoor Generator

Output capacity is 300W, with a very impressive 600W peak load rating. The only downside is the smaller battery. The lithium ion battery inside the Rockpals provides 280 WH, this almost half that of the Jackery Explorer 440 or Yeti 400. The advantage is a much lower weight of 7.3 pounds, but you have about 60% of the runtime compared to the other two. So, you can’t expect much more than 4-hours if you’re using a 32” LCD TV. You’ll be able to charge a cell phone about 25 times, before running out of battery power.

It takes 6 – 7 hours to charge the battery, using the 110V AC charger and you have about 78W through current when the battery is charging. So, you can continue using low-wattage equipment, like a laptop, whilst charging the internal battery. It has a 12V car charge input, that also accepts a nominal 12V solar panel. Using a car battery, it will take about 6 -7 hours to fully charge the Rockpals, a 60W solar panel will take about 10 – 11 hours to fully charge the battery. Real world testing of the solar charger reveals an efficiency of around 75%. This is certainly not the best and cannot compete with the MPPT solar chargers fitted to the other two 300W indoor generators featured in this review.

The Rockpals has a single 110V AC output socket, supplied by a pure sine wave inverter. DC outputs include an 8A cigarette lighter style 12V DC socket, 3 X 4A 12V DC outputs, and a 24V DC 3A outlet. It also has 2 X QC 3.0 USB ports and 2 X 5V (3.1A) USB ports. Two bright LED flashlights, with separate control switches are a handy addition.

The LCD screen provides most of the essential information, output and input wattage and battery status by means of a battery with charge lines. It doesn’t show exact battery percentage though, the battery indicator really just gives an approximate (25%, 50%, 75%, 100%) indication.

For the lower price tag attached to the Rockpals RP300W indoor generator, the shortcomings aren’t that noticeable. It has a smaller battery with fewer ampere-hours, and a less than ideal solar charger. The redeeming feature may be the higher peak wattage and lightweight design (mostly due to the smaller battery). This is a solid little machine and can be taken anywhere with ease.

More About Indoor Generators

Although marketed as generators, these are not, strictly speaking, generators at all. A portable battery power station does not generate electricity, it stores power in a battery and then supplies electricity from the battery. A generator uses mechanical power to generate electricity, a battery power station (or indoor generator) stores kinetic energy and converts this into AC electricity using an inverter. Understanding an indoor generator is all about understanding inverters.

What is an Inverter?

An inverter converts Direct Current (DC power), usually stored in a battery, into Alternating Current (AC power). There are two methods used to achieve the power conversion. The simplest, and oldest method is a switch mode inverter using Metal Oxide Semiconductor Field Electric Transistors (MOSFET). Engineers sure like to use long and difficult terms to describe stuff. The second more modern method is also a term that most can’t get the hang of: Internal Gate Bipolar Transistors (IGBT) are more modern, computer-controlled inverters. These are much more efficient and produce a pure sine wave.

Switch Mode Inverters

These inverters have been around the longest and use very basic technology. The simplest switch mode inverter creates a square sine wave. By using two MOSFETs to switch the DC current across two poles, an AC pulse is generated. It is called a square wave because, when viewed through an oscilloscope, the sine wave is square. A true sine wave, like those produced by a large gas-powered generator is an elliptical curve. It has a wide base, tapering to narrow curved apex.

Square sine wave inverters are hardly ever used anymore because they are inefficient, and the square wave is not ideal. Any electric equipment used with a square sine wave will produce excessive heat and noise. This not only wastes energy but can harm some appliances. There are some appliances that won’t function at all when powered by a square wave inverter.

To improve performance and efficiency, additional MSFETs can be used to produce multiple square waves. Each consecutive square is smaller than the preceding one. By stacking these decreasing squares on top of each other, the wave resembled steps. This is known as a step square, or modified sine wave. The more steps used, the more it will resemble a true sine wave square. Though, with each additional MOSFET, the inverter becomes heavier and more expensive. Modified sine wave inverters seldom have more than 3 steps (6 MOSFETs). While these inverters are more efficient and provide a better sine wave than square wave inverters, they still don’t provide a true sine wave. Essentially, they have the same inefficiency and operating properties of a square wave inverter. The issues are simply reduced with each step in the square wave.

IGBT Inverters

If we were to get really technical, IGBT inverters also generate a modified sine wave. However, the multitude of steps used, resemble a true sine wave. In comparison to a modified sine wave with only a few steps, IGBT invertors use thousands of steps, making them undetectable when using an oscilloscope. They, therefore, function in exactly the same way as pure sine wave generated by an alternator. In fact, the resultant wave is better than one can usually expect to find when measuring the AC current supplied from the grid. In other words, a pure sine wave (IGBT) inverter provides the cleanest power possible with the lowest Total Harmonic Distortion (THD). When people talk about “dirty power” harming electronic equipment, this refers to high THD levels. I consider 5% THD, or less, to be good power than won’t damage these appliances.

THD refers to imperfections in the sine wave caused by fluctuations in the frequency and voltage. An IGBT inverter uses sophisticated transistors, combined with capacitors, to produce a constant pure sine wave. The general standard for these inverters is a THD reading of less than 3%. Some are as low as <1%. Because the inverter has an onboard computer monitoring the current constantly, minor changes in frequency and voltage are corrected within less than a 60^th of a second. I’ve done many tests, measuring the voltage and frequency that is supplied from the grid. The grid power supplied to your home can have THD levels close to 10%, in some areas even higher. Most gas-powered generators (that don’t use an inverter) produce THD levels of 25% or more. This is why these generators are not recommended for TVs, computers, or any electrical equipment with electronic circuitry. This would mean any appliance with an LCD screen or soft touch controls.

Pure sine wave inverters are, therefore, much better for your electronics. They are also more efficient and offer higher surge capabilities. This makes these inverters more capable when starting electric motors (pumps, refrigerators, and air conditioners), as well as other inductive loads, like microwaves and fluorescent lights.

Understanding Batteries

Of the numerous rechargeable batteries on the market, only two types are extensively used for indoor generators, or portable battery power stations. Lithium Ion batteries are widely considered to be the best batteries available today and are rapidly becoming the battery of choice for indoor generators. The other option would be lead acid (deep cycle) batteries. A more environmentally friendly alternative to lead acid batteries are calcium gel batteries. Because these batteries have the same characteristics as lead acid batteries, you can view them in the same way. It’s just that the lead has been replaced by calcium, which is not toxic.

Lithium Ion Batteries

Used in everything from mobile devices to battery-powered tools, lithium ion batteries have become the most popular portable power source in use today. The fact that these batteries have a wonderful ratio between density and mass to their power output, is the main reason why they are so popular. A relatively small, lightweight battery can provide a large number of ampere hours (AH).

Apart from their efficiency, lithium ion batteries are much more accommodating when it comes to battery cycles. The term battery cycle refers to the number of times a battery can be discharged and recharged. A full battery cycle is running from full to charge to complete discharge and then back to full charge again. A 50% cycle means only discharging a battery to half its capacity and then recharging it to full. So, when you see a battery rated for 500 cycles, it means the battery can be completely discharged and then recharged a total of 500 times before it needs to be replaced. This cycle time will usually be accompanied by a percentage. If, for example, the spec is 500 cycles at 80%, it means that the battery will last for 500 cycles at an average discharge rate of 80% of its total capacity before recharging.

Most rechargeable batteries deteriorate rapidly as a result of irregular cycles. This means that the battery should be completely discharged and then recharged to full every time they are used. These batteries also deteriorate when stored for prolonged periods, especially if stored when not fully charged. This does not apply to lithium ion batteries. Depending on how they are manufactured, lithium batteries can be stored for up to a year without needing to be placed on charge. Furthermore, you can store these batteries when they are not fully charged.

The only disadvantage to using lithium ion batteries is their cost. These are the most expensive batteries that you can buy. Fortunately, we have seen prices for these batteries drop over the years.

Lead Acid Batteries

Included among standard lead acid batteries, we can also list Absorbed Glass Mat (AGM) batteries and calcium gel batteries. I’ve already explained the difference between calcium gel and conventional lead acid batteries in the introduction to this section of the article, so I’ll briefly explain AGM batteries. These batteries were first developed for solar applications that need to allow for exceptionally long charge and discharge cycles. By using a glass matt and a gel, these batteries have improved cooling abilities, and this increases their lifespan during charge and discharge cycles. AGM batteries are usually more expensive than conventional lead acid batteries, but should last longer. Other than this, they function in the same way.

Lead acid batteries are preferred as a cheaper type of rechargeable battery. They are, however, very heavy. This makes them less than ideal for portable equipment. One also has to pay more attention to maintenance when dealing with lead acid batteries. Although most are sold as maintenance-free sealed lead acid batteries, this merely means that you don’t need to add water or acid over the lifespan of the battery. Lead acid battery maintenance centers around charging, discharging, and storage.

No battery is more affected by irregular cycles than a lead acid battery. Leaving a lead acid battery for any length of time at low charge can destroy the battery in short period of time. It is essential that you charge the battery to full immediately after every use, at least within 24-hours. Another issue with these batteries is a high level of self-discharge. This means that when a lead acid battery is stored, it starts to lose charge. A lead acid battery should always be stored at full charge and then placed on charge at least every three months.

An important, and often overlooked, maintenance requirement for lead acid batteries, is regular maintenance cycles. Every year, or every 100 cycles, a lead acid battery needs a maintenance cycle. This entails a gradual discharge until the battery reaches full discharge and then a full recharge. This re-energizes the electrolytes and prolongs the battery life.