What is Tesla Powerwall? ǀ The Full Story Behind Tesla Home Power Storage
Since 2012, When Tesla began development of the Tesla Wall, this technology has been the topic of many discussions around renewable energy and power storage. Since then, we’ve seen the second generation Tesla Wall 2 and there’s a lot of talk about the next upgrade, Tesla Wall 3. But what exactly is the Tesla Wall? How does it work? An important question for most consumers; is it worth installing a Tesla wall, will it actually save you money on your electricity bills?
This article is all about Tesla wall, what it is, where it began, and where it is heading. If you have questions about Tesla Wall technology, here is where you’ll find the answers.
Explained | What is Tesla Powerwall?
Essentially, Tesla Wall is an advanced and efficient battery designed to store electricity for homes and commercial buildings. Used in in conjunction with an inverter, the DC power stored in the battery system can be used to power all your household appliances. The Tesla Wall battery is compatible with most solar inverter and uninterrupted power supply systems.
The thinking behind the Tesla Wall has 3 main objectives, aimed at meeting the needs of different electricity consumers.
- Provide emergency backup power during an outage.
- Manage power consumption to save on electricity bills during peak metering periods.
- Store and Supply power for off-grid solar power systems.
Is the Tesla Wall different from other solar batteries?
When the first generation Tesla Wall (Tesla Wall 1) entered the market in 2015 it was, arguably, the most advanced DC power storage system in the world. Traditionally, solar batteries used Absorbed Glass Mat (AGM) deep cycle batteries. These batteries use old-fashioned chemicals, like lead acid with improved cooling to allow for an improved lifespan over longer discharge and charge cycles.
The Tesla wall offered a much more efficient battery, with improved cycle capabilities. The Tesla battery uses Lithium Nickle Manganese Cobalt Oxide (LNMC) as the basis for the battery’s chemistry. It is one of the most commonly used structures for a lithium ion battery. This is mostly because of the high energy density the battery provides. In other words, less volume – more power.
Tesla improved on the basic technology by including sealed liquid cooling. By controlling the battery temperature, the Tesla Wall can guarantee a longer life and improved efficiency of 92% and a 10-year warranty for 5,000 cycles, with a 100% discharge capacity. To understand what all this means, we should look at how batteries are evaluated.
The power a battery provides is measured in watts (W) or kilowatts (KW). There are two ways of using this information, the total amount of power that can be used at any given time and the amount of power actually stored in the battery.
Usable power, expressed as kilowatt-hours (KWH), is the amount of power available to be used from a single battery charge cycle. The Tesla Wall 2 is rated for 13.5 KWH. This means that if you’re 13.5 KW power in your home, the battery will supply power for 1-hour before it needs to be recharged. At an average power consumption of 6KW, you can expect just over 2-hours of battery usage before recharging.
A battery cycle defines how the battery is used. A cycle consists of 3 stages: charge, discharge, and recharge. So a full battery cycle will be the power it takes to charge the battery to full capacity, the amount of power that is used, and the amount of power needed to restore the battery to full charge.
The depth of a cycle is determined by what percentage of the total battery capacity is used during a discharge cycle. If a battery is rated for 10KWH, and you use 5KWH, your battery has gone through a 50% cycle.
Most batteries experience a loss of voltage as the battery approaches 100% depth of discharge, or full discharge. Lithium-ion batteries are preferred for their ability to maintain usable power down to 100% discharge.
Deep cycles, beyond 50% of full capacity, also take a toll on battery life for most rechargeable batteries. So deep cycles will shorten the battery lifespan. Lithium ion batteries are not affected by cycle depth or time between recharging cycles. So these batteries will last longer over deep discharge and longer recharge cycles.
An adaptable cycle, as is the case with lithium ion batteries, is the best for a solar power system. Long periods without much sunshine will result in total discharge or close to 100%. The battery may only recharge partially, it can take several days of interrupted sunlight to fully charge the battery. Lithium ion batteries are the only battery type that will not be adversely affected by these erratic charge cycles.
This is the maximum power a battery, or inverter, is able to provide. Most batteries are capable of providing a high output, more than one would ever expect to use to supply power for any household appliance.
Power output is most applicable when using a DC-AC inverter. This converts the DC power of a battery to the AC power we use in our homes. An inverter will have a limited peak and continuous power output rating. Peak power being the maximum amount of AC power the inverter is able to provide for a short period. Continuous power is the maximum amount of power the inverter can provide continuously.
Tesla Powerwall 1
This was the first version of the Tesla Power Wall, developed in 2012. The Tesla Wall 1 consisted of a DC battery pack with a 6.4 KWH capacity. The Power Wall included a DC-DC converter, or charge controller, allowing the battery pack to be connected to standard solar panels.
The Tesla Wall 1 did not include an AC inverter, so could not be connected directly to your household power. However, the battery pack is compatible with most solar inverters and uninterruptible power supply systems.
- Tesla Powerwall 1 Price: ± $3,000 (not including additional hardware and installation)
- Tesla Powerwall 1 Dimensions: 51.3” X 34” X 7.2”
- Tesla Powerwall 1 Capacity: 6.4 KWH per battery pack. Up to 10 Powerwall packs can be connected for a maximum total capacity of 64 KWH
- Tesla 1 Warranty: 5,000 cycles, 10-years or more for normal household use. A 100% cycle every day, is 3,600 cycles over 10-years.
Tesla Powerwall 2
The Powerwall 2 has two significant improvements on the original Powerwall 1. Capacity has been increased and an AC inverter has been included. This means that the Tesla Powerwall 2 can be connected to the main power supply. It is charged using AC power from the grid and provides AC power for the home during an outage, without the need for an additional inverter-charger.
When using solar panels, an additional solar inverter is required to convert the DC solar charge into AC power. This conversion reduces efficiency and places the Tesla Powerwall2 at a disadvantage when compared to competing solar hybrid systems. I’ll discuss these factors in more detail when we look at alternatives to the Tesla Powerwall.
Despite providing more than double the power, and the inclusion of an AC inverter, the Tesla Powerwall 2 is much more compact than its predecessor.
- Tesla Powerwall 2 Price: ±$6,400 (not including additional hardware and installation)
- Tesla Powerwall 2 Dimensions: 45.3” X 29.6” X 5.75”
- Tesla Powerwall 2 Capacity: Battery storage – 13.5 KWH; AC output – 7 KW peak and 5 KW continuous power. Up to 10 Powerwall 2 packs can be connected to provide 135 KWH batter storage and 70 KW peak / 50 KW continuous AC output.
- Tesla Powerwall 2 Warranty: Unlimited cycles, with guaranteed 70% of the original capacity after 10-years (solar self-use and backup only).
Tesla Powerwall Gateway
In order to use the Tesla Powerwall 2 as a backup system for power outages, the Backup Gateway is required, costing around $1,700. This is a monitoring and control system that allows you to control the system, set parameters, and isolates the backup circuits during an outage for electrical safety. The Tesla Backup Gateway is not designed for off-grid applications. It is also 3-phase compatible, with high-speed 4G internet connectivity for use with the Gateway App.
Now in its second generation, the Backup Gateway 2 is more sleek looking and compact. It also has many functions that allow the user to customize the Tesla Powerwall 2 to meet their needs. Depending on your priorities, you can choose to maximize backup storage capacity. This will ensure that the batteries remain charged to full capacity. This is preferred for users who primarily use their Tesla Powerwall as an uninterruptible power supply for outages. For maximum savings, when using solar panels, the user may choose to run maximum battery cycles, thereby using less power from the grid and more stored power generated by the solar panels.
Together with the Gateway mobile app, there are several advanced features to promote battery efficiency and lifespan. To overcome the tendency of lithium ion batteries to be less efficient in cold weather, the Gateway can be programmed to heat the battery, shortly before sunrise on cold mornings. This will allow more efficient early morning solar charging in cold climates. The user also has timer options, this allows for maximum cost savings in areas where electricity costs are higher during certain peak periods. You are able to ensure maximum battery capacity before peak metering rates are applied and then use stored battery power during the high-cost period. All this can be controlled remotely using the Tesla Gateway App.
Tesla Powerwall 3
As early as 2018, there has been much speculation surrounding a new version, Tesla Powerwall 3. However, despite many opinions as to how Tesla Powerwall could be improved upon, there has been no announcement from Tesla with regards to a 3rd generation Powerwall. Though the company is known for dramatic, last minute, press announcements. This could be a strategy to gain the most publicity. It could also just be the way of tech research and development. When spending billions of dollars on R & D, tech companies are understandably reluctant to reveal new developments too early. Proprietary information and all of that. No one wants the competition to catch onto what they’re planning next.
In my opinion, Tesla has fallen behind in the hybrid power storage field. A hybrid charger and inverter system refers to a power generation and storage system that charges batteries using either AC power from the grid or generator (for off-grid systems) and DC power from solar panels or some other form renewable energy, like wind.
Most hybrid battery power packs are more suited to adaptability, when compared to Tesla Powerwall, especially for off-grid or solar priority systems. Because the Tesla Powerwall 2 cannot be linked directly to solar panels (a solar charger inverter is required), it is a more complicated, and more expensive, installation. The cost and effort of installing a solar charger and inverter is not necessary for most hybrid inverters. It also means a loss of power. The DC current from the solar panels needs to be converted into AC power as this is the only input current that can be used to charge the Tesla Powerwall. It is then converted back into DC, which is the current used by the battery for storage. Finally, the electricity is then converted back into AC power for use in our homes.
Most hybrid inverter battery systems allow for solar panels to be connected directly to an inverter charger module. These systems will usually have external batteries. This allows the user to connect any type of 12V deep cycle or lithium ion batteries. The amount of batteries can specified for the amount of storage required. Usually several inverters can be connected in parallel to supply the requisite wattage for a few emergency circuits or the whole home, even large commercial applications.
While Tesla may have the best looking, and most compact system. It is more geared to home backup power. It does provide maximum benefits for solar power generation. My guess is that when Tesla introduce Powerwall 3, it will have a direct DC input for solar panels. No doubt, Powerwall 3 will have more power and more programmable features, using an improved Gateway module and mobile app.
Learn about the latest Tesla Powerwall by visiting their site.
Is Tesla Powerwall cost effective?
I spent many years in the alternative power business and the argument for and against solar power, in particular, is riddled with complications. To be honest, I’m not entirely sure if it’s worth the initial financial outlay in many cases. Some have called the Tesla Powerwall a novelty for rich greenies who need to show off their commitment to solving climate change. As for the environmental issues, that will be discussed later.
I’ve done countless cost assessments for various types of solar and hybrid systems in different areas. One thing I can say for sure is that all the factors need to be considered. I have a quick checklist of important considerations when deciding on the viability of using renewable energy for a home or business:
- Local metering cost $/KWH
- Subsidies and rebates for solar installations
- Utility company buy-back rates for user power generation. In some areas, environmentally conscious local authorities will buy back power generated by homeowners at a premium rate, allowing these homeowners to profit from supplying low carbon footprint power to the grid.
- Distance from a grid power supply. In remote locations, the cost of connecting to the grid can exorbitant. If a lodge or home is many miles from an existing power supply, the cost of installing a solar power system, along with no long term electricity bills, can make an off-grid system more cost effective.
- Amount of daily sunlight through the year. Solar efficiency is a key factor, when considering both financial and environmental viability. In areas that that don’t receive much sunlight on a daily basis, solar power is not that viable. Ironically, in northern Europe, where solar power is least viable, it is most popular. This is because of government incentives for renewable energy that will reduce their carbon tax burden.
For urban and suburban use of solar power, the most important factors will be local electricity prices and incentives, like rebates and power buy-back rates. When considering Tesla Powerwall as part of a solar generating system for your home, you need to consider all the costs involved: Tesla Powerwall 2, Powerwall Gateway, solar panels, installation and materials.
To supply a home with a single (5KW) Tesla Powerwall 2, the required additional hardware, solar panels, and installation, you’ll be paying around $10,000 – $15,000. When you consider that the average US home requires about 7,000 to 10,000 KW to supply all electrical needs, this price will double for a complete (full-house) solar electrical system, taking the cost of the Tesla Powerwall, panels, and hardware up to $20,000 to $30,000. Now we’re talking some big money.
To put this cost into context, we need to consider the factors I listed above. If you’re looking at the real cost of a complete Tesla Powerwall system vs payback over 10 – 15 years, you need to first take into account any rebates. For example, the California HERO payback system allows homeowners to finance a solar power system and pay it back through their property tax. You should do research into all state, county, and municipal incentive schemes before deciding on the actual cost. Most installers are familiar with these and will help with the applications.
Once you have a realistic idea of the actual cost to you, as the homeowner, you can see how this compares to your electricity bills over the next 10 to 15 years. The Tesla Powerwall is guaranteed to last at least 10-years for a home solar power system, by which time the batteries will still be supplying a minimum 0f 70% original capacity, easily allowing for a 15-year payback period.
In states like California, that have attractive incentives for renewable energy, a solar-powered Tesla Powerwall is usually a great benefit and should save a lot in real terms.
Is the Tesla Powerwall really environmentally friendly?
This is another area where I’ve had long arguments with my colleagues in the renewable energy business. I’m not sure it is always the green option to use solar power. Purely as a backup system, without solar panels, there is no environmental benefit to using a Tesla Powerwall. In these instances, it is quite the opposite, only providing the convenience of power backup during an outage.
So the real question comes down to the environmental sustainability of solar panels. A little known fact is that there is a limited supply of silicon that is of a suitable grade for poly-crystalline solar panels. Cheap, mono-crystalline solar panels cannot be considered green. They don’t last very long and aren’t efficient. This means that the manufacturing footprint for cheap solar panels is greater than the energy they provide over their expected lifespan. Even poly-crystalline solar panels vary in their efficiency, making only the more expensive options truly viable in terms of environmentally sound lifespan.
It is estimated that the total silicon reserves on the planet, if used for the manufacture of solar panels, will provide for about 23% of our current electricity demand globally. When you account for increased future energy demands in developing countries, and our growing dependency on electricity for new technology, like electric cars, this figure could be half the current estimate in ten years or less. So, solar power will never be a complete solution for our electricity needs.
We then need to look at the environmental effect of quarrying all this silicone from the surface of the earth. What will be the long term effects of removing thousands of tons of tons of dirt, leaving behind massive craters?
Other factors, like transporting raw materials and the energy required to manufacture solar panels, as well as additional materials, like aluminum and copper, also need to be accounted for. However, with responsible management, these factors need not detract from the 20 – 30 year energy efficiency of high-grade poly-crystalline solar panels, as long as these panels actually produce the energy that that they are theoretically capable of.
In my opinion, solar panels in an area that doesn’t receive sufficient sunlight, are a waste of money and serve no environmental benefit. Short winter days, snow, and heavy cloud cover reduce the effective use of solar panels to a point where the energy produced cannot be justified by the energy input during manufacturing. Let alone other factors, like the impact of obtaining the raw materials.
All the statistics used to promote the use of solar panels, are derived from testing in ideal situations. In a desert environment, solar panels are extremely efficient, making them ideal. In far northern areas, solar panels on the roof of your house are no more than a politically correct statement. In reality, you are doing more environmental harm than good. At least, this is my opinion after many years of research into the viability of using solar energy.
Alternatives to the Tesla Powerwall
Tesla faces countless competitors in two market sectors: backup uninterrupted power supply and solar hybrid power supply. These are two distinctly different applications and alternatives to the Tesla Powerwall need to be separated into these two categories.
Backup Power Supply
If you’re looking merely for a convenient way to supply backup power to your home, without using solar panels, Tesla Powerwall can be considered one of the best options. There are many manufacturers of uninterruptible power supplies, using an inverter, charger, and batteries. These can range from really cheap units, to incredibly expensive.
Taking into account quality, electrical efficiency, and battery lifespan, Tesla Powerwall is probably the best and relatively inexpensive. Some may be taken aback by this this statement, as Tesla Powerwall isn’t exactly cheap. However, from many years of experience in this industry, I know what the costs involved are, and how to measure initial purchase price against long term value.
First of all, cheap inverters don’t last, and many can’t handle inductive load, limiting what you can use them for. Basically, I’d never buy a cheap inverter. Furthermore, there’s the question of efficiency. Tesla Powerwall is rated at around 92% efficient. This means very little power is lost through conversion. Less efficient, cheap inverters will increase your electricity consumption when charging the batteries and reduce the amount of usable power that is stored.
The most significant benefit to using Tesla Powerwall for home backup power is the superior battery technology. I’ve found that the largest long term expense with uninterrupted power supplies is battery replacement. When used for power backup, really cheap deep cycle batteries might only last a year, at most 3-years, if you’re lucky. Even the best AGM batteries seldom last more than 10-years, and they’re not cheap. Most of the readily available, higher quality deep cycle batteries last around 5-years when used for backup emergency power. I’ve found that the cost of replacing these batteries is the biggest drawback. Enough storage capacity to supply a home with backup electricity for around four hours will cost $3,000 to $4,000. Spending this much on battery replacement every 5-years, sort of puts the price into perspective. When you’re looking at a guaranteed 10-year, probably 15-years, for the Tesla Powerwall, the price starts to make sense.
Hybrid Solar Power Supply.
Although the Tesla Powerwall is among the better options for high quality battery storage when using hybrid and off-grid solar systems, there are better options. Albeit usually more expensive. The main reason why Tesla Powerwall is not as competitive for the solar market, is the fact that they have not been designed for direct solar panel input. The Powerwall can only be connected to an AC power supply. This requires solar input power to be first converted into AC before connecting to the Tesla Powerwall.
A hybrid inverter, designed for solar and AC grid-linked operation, usually has a built-in MPPT solar charger. This makes the most efficient use of every amp generated by the solar panels. A purpose-built solar hybrid inverter-charger will be more efficient than a Tesla Powerwall. That is to say a quality product, which would obviously be quite expensive.
It is widely considered that Enphase Energy is the leader in solar and hybrid technology. This is a California based company, a state that has long been associated with the development and promotion of renewable energy. Enphase has developed a hybrid solar system, with lithium ion batteries that is probably the most efficient in the world, 96%. This beats the Powerwall 92% efficiency when used as an AC charger. If we then consider a further loss when converting the solar power into AC, so that it can be used with the Powerwall, we see Enphase emerge as the outright winner.
I’ve long been a fan of the Dutch manufacturer, Victron. However, these are large heavy industrial-grade inverters. They don’t have the compact elegant design that make the Tesla Powerwall so desirable. What I like about Victron hybrid inverters is their indestructible design. The batteries are sold separately, so you can use any type of 12V battery. Another manufacturer of rugged off-grid and hybrid inverters is the Australian company, Outback Power. These are also tough, and a little more aesthetically pleasing than the bulky Victron. Though no one can compete with Tesla for elegance and style, which can important if your system is visible within the home.