tesla powerwall review

The Tesla Powerwall home battery complete review

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Back in 2015, automaker Tesla Motors set its sights on the home energy storage market and announced the launch of its home battery product, the Tesla Powerwall.

In the past, Tesla Motors has been praised for making high-quality electric vehicles, as well as for their ability to reimagine and successfully rebrand existing technologies. In fact, while Tesla’s automobiles revitalized the 21st-century electric vehicle market, the first electric cars were invented more than a hundred years earlier. 

Tesla’s rebranding of residential-use batteries is in line with their legacy of reimagining existing products. Tesla’s battery may represent the first time in history that everyday homeowners are truly excited about the potential of storing energy at their home. The Powerwall, combined with the exciting Tesla Solar Roof, are both potential cornerstones of Elon Musk’s sustainable energy vision for the future.

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How does the Tesla Powerwall work?

The Tesla Powerwall pairs well with solar panel systems, especially if your utility has reduced or removed net metering, introduced time-of-use rates, or instituted demand charges. Installing a storage solution like the Tesla Powerwall with a solar energy system allows you to maintain a sustained power supply during the day or night, as long as you store enough power from your panels when the sun is shining.

As with many other home battery products, the Tesla Powerwall is sized for day-to-day use at your home and is often paired with a solar panel system. When your solar panels produce more electricity than you can use in your home, you can store the excess electricity in the battery system instead of sending it back into the grid. Later, when your panels aren’t producing enough electricity to meet your home’s needs, you can use the electricity stored in your battery instead of having to buy it from your utility company.

Key things to know about the Tesla Powerwall

Tesla describes the Powerwall as a “rechargeable lithium ion battery with liquid thermal control.”  It is one of a few companies in the residential energy storage market that makes small-scale batteries for home energy storage. The first-generation Powerwall launched in April 2015, and an updated Powerwall 2.0 was announced in October 2016.

When evaluating the Powerwall, there are various important metrics and technical specifications to keep in mind. Among the most important are the size of the battery (power and capacity), its chemistry, depth of discharge, and roundtrip efficiency

Size

The Tesla Powerwall comes in only one size of 14 kilowatt-hours (kWh). Two important metrics to keep in mind when comparing the Powerwall to other home storage options are power and usable capacity. Power (measured in kilowatts, or kW) determines the maximum amount of electricity that can be output at a single time, while usable capacity (measured in kilowatt-hours, or kWh) is a measure of the maximum amount of electricity stored in your battery on a full charge. The Tesla Powerwall boasts a maximum power rating of 5.0 kW to go along with 13.5 kWh of usable capacity

Importantly, the Powerwall system is also modular, meaning you can add multiple battery products to your storage setup. For example, you might want to install multiple Powerwall batteries for a home with high energy demands. The Tesla website indicates that you can add up to 10 Powerwall batteries together to form one massive storage system.

Think of your battery like water running through a pipe. The usable energy capacity is the amount of water available to push through the pipe, while power is the size of the pipe itself. Larger pipes allow more water to flow through at once, which depletes the water faster. Similarly, a battery with a high power rating can deliver more electricity at one time, but will burn through its available energy capacity faster too.

A battery’s power determines what appliances you can run with it at the same time, while usable capacity determines how long those appliances can be run. Batteries with a higher power rating are capable of powering more robust appliances or many appliances at once, while batteries with a higher usable capacity can store more total energy and thus can run your appliances for longer periods of time without needing to recharge.

Basic functionality

The functionality of one solar battery next to another can vary; some batteries have excellent off-grid capabilities, while others offer software solutions specific to rate arbitrage. Here are the important qualities of the Tesla Powerwall:

Backup power

Tesla has made a concerted effort to ensure their battery solution is compatible with most common brands and types of off-grid and hybrid inverters. This means that, as long as your installer installs the correct components, your Tesla Powerwall battery will be able to provide backup power for your home when the grid goes down.

Chemistry

The Tesla Powerwall is a lithium-ion storage product; specifically, it is a lithium nickel manganese cobalt oxide (NMC) battery. This is one of the most common lithium-ion battery technologies, and for good reason: relative to other types of batteries, LFP batteries are known for their high energy density (the amount of energy they can store relative to the physical space they take up) and increased safety. To learn more about how different lithium-ion battery chemistries stack up against one another, check out our overview of battery chemistry differences.

Performance metrics

Two key ways to evaluate the performance of a solar battery are its depth of discharge and roundtrip efficiency

Depth of discharge (DoD) indicates the percentage of a battery’s energy that has been discharged relative to the overall capacity of the battery. Because the useful life of a battery decreases each time you charge, discharge, and re-charge–or cycle–your battery, many battery manufacturers specify a maximum DoD level for optimal battery performance. In general, batteries with a higher depth of discharge are considered better quality products. The Tesla Powerwall boasts a depth of discharge of 100 percent, reflective of its remarkably safe and advanced NMC battery chemistry.

Roundtrip efficiency is a measure of electrical losses involved with charging and discharging a battery. The higher the efficiency percentage, the more efficiently the battery is able to convert incoming electricity into stored electricity and then back into usable electricity. The Tesla Powerwall has a high roundtrip efficiency of 90 percent; this means that for every 10 kilowatt-hours (kWh) of electricity you put into the battery, you’ll receive 9 kWh of output.

Tesla Powerwall warranty coverage

Tesla Powerwall warranties

  • Warranty period: 10 years
  • Guaranteed end of warranty capacity: 70%

In most cases, homes with a Tesla battery will charge and discharge their battery every day. The Powerwall comes with a 10-year warranty. Tesla guarantees that the battery will maintain at least 70 percent of its capacity to hold a charge during that time period. 

Tesla’s battery technology is similar to other rechargeable batteries both large and small: as time goes on, the battery loses some of its ability to hold a charge. Think of how the battery life of a brand-new smartphone compares to one that is a few years old. As you continually charge and drain your phone’s battery, it starts to lose some of its ability to hold a charge.

The battery life of your Powerwall battery will deteriorate in the same way. That isn’t an indicator of a product flaw – all batteries lose some of their ability to hold a charge over time, whether it’s an electric vehicle battery, a home energy battery, or a rechargeable AA battery. This is why Tesla offers a warranty that guarantees a certain percentage of storage capacity ten years in the future.

Warranty, capacity, and power are three of the most important metrics you should consider when comparing home battery options. If you’re curious to learn more about the best way to perform your own battery comparisons, check out our video explaining how to evaluate your home energy storage options:

If you want to compare individual battery models side-by-side, our battery Buyer’s Guide lets you select products and compare them based on efficiency, capacity, power, and more.

Tesla Powerwall cost

Tesla lists the Powerwall at a cost of $7,000 alone, and puts supporting hardware costs at $1,000, bringing the price of just the Powerwall and its associated components to $8,000 before installation.  As a rough estimate, you can expect the Tesla Powerwall to cost between $9,600 and $15,600 for a full system installation (before incentives). That number includes the battery, an inverter, various other equipment costs, and estimated installation costs. The cost of installing a battery isn’t as straightforward as looking up the list price for an individual component–i.e., your battery. In fact, depending on your electrical setup, among other factors, installation costs can vary widely.

If you want to install the Powerwall as part of a solar-plus-storage system, battery costs are just one part of the equation. A 5 kilowatt (kW) solar energy system costs anywhere from $9,000 to $15,000 depending on where you live and the type of equipment you choose.

That may sound like a lot of money, but installing a solar-plus-storage system can be a worthwhile investment. Whether or not the Tesla Powerwall makes sense for you is determined by the way that your electric utility structures its rates, as well as your reasons for installing a solar battery.

In some cases, depending on where you live, you may have access to financial incentives that can reduce your home energy storage installation costs. For instance, if you live in California, you could get a cash rebate that covers most of your home battery costs through the Self-Generation Incentive Program (SGIP). Other states (such as Massachusetts) are in the early stages of evaluating battery storage performance incentives as well, and several states already provide cash rebates.

Can you go off-grid with the Tesla Powerwall?

Installing a solar-plus-storage system at your home is a great way to take control of your electricity bill, but it doesn’t mean that you’re completely disconnected from your utility. Going “off the grid” with solar batteries is actually a more expensive and complicated proposition than you might think. Most home batteries, including the Powerwall, only have enough capacity to store a few hours of electricity. If you want to make sure you can maintain power to your property for days at a time, you’ll need to install several Powerwall batteries together to increase your storage capabilities.

Where to buy the Tesla Powerwall

The Tesla Powerwall battery is currently available online through Tesla’s website and through any solar and/or energy storage installation company that carries the Powerwall in their inventory. Adding energy storage technology to your home is a complicated process that requires electrical expertise, certifications, and knowledge of the best practices required to install a solar-plus-storage system correctly.

A qualified EnergySage-approved company can give you the best recommendation about the Tesla home battery system and other energy storage options available to homeowners today. If you are interested in receiving competing installation quotes for solar and energy storage options from local installers near you, simply join the EnergySage Solar Marketplace today and indicate what products you’re interested in your profile’s preferences section.

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About Jacob Marsh

Jacob is a researcher and content writer at EnergySage, where he focuses primarily on current issues–and new technology!–in the solar industry. With a background in environmental and geological science, Jacob brings an analytical perspective and passion for conservation to help solar shoppers make the right energy choices for their wallet and the environment. Outside of EnergySage, you can find him playing Ultimate Frisbee or learning a new, obscure board game.

55 thoughts on “The Tesla Powerwall home battery complete review

  1. AvatarFrank Ergin

    I see where it says the cost is between $9 and $15K, but Tesla rep came out and gave a quote for $26K with $7K rebate, still owing almost $20K for 2 batteries. Why the big difference.

    Reply
    1. AvatarMtg

      So 2 batteries and components cost $16,000. Price quoted is for one battery, components and installation. Based on the range, installation is between $1600 and $7600. Assume that you pay 50% less on labor for the second battery installation and that is $3800. Total labor cost of $11,400. With two batteries, $27400 total cost. Sounds like their estimate is spot on. If you are in a market with either strong demand for solar and battery installation or not enough installers available, your cost for labor is on the higher end. Good news is with rebates you are only paying $5k for installation.

      Reply
    2. AvatarJohn Almond

      Hey Frank,

      You probably didn’t consider the additional costs for other parts to the Tesla Powerwall or additional upgrades required, such as the electric main panel, or hidden conduit.

      Tesla usually does not add that in until after they speak with you. The big thing is what you are powering with the Powerwall.

      For example, with 1 Powerwall, it’s good for main electrical panel items such as lights, electrical outlets, etc.

      With 2 Powerwall, you get the same with one + the ability to power additional large appliances such stove/oven, central air conditioner, etc.

      With 3 Powerwall, the ability to power additional appliances extends quite a lot.

      My suggestion is to always ask what is the full service cost versus just a cost for the Powerwall as you will get a more honest reply and answer.

      Reply
  2. AvatarDean McQueen

    I’ve had a Powerwall 2 for over a year and when my neighborhood’s power went out at 8am, with over 50% charge, the Powerwall died and didn’t even cut me off from the grid so I could run off my solar. The Tesla repair guy said it wasn’t caused by the outage, even though it was working fine right before the outage. Huh? I’ve now been waiting a month for a new Powerwall. I asked Tesla if I could get any compensation for their expensive product failing me during an outage and being without a backup for a month. No dice. Could I return the POS? Nope. With my Model 3 being a complete disaster and now this, I’ve lost all faith in Tesla.

    Reply
    1. AvatarBrian A Roach

      Thanks for the heads up concerning “warranty” on something they advertise to last 10 years. Tesla PW is being offered by our contracted proposal from SunPro. I am postponing the addition of Tesla PW until later 2021. I hold BLNK stock and am reviewing their charger options (AC and DC), battery offering and by then any new R&D from them may give me an option to Tesla PW.

      Reply
  3. Avatarmad_science

    This is a great summary for the spec sheet and costs, etc, but was hoping to get an actual review. As in, a real-world experience with it. That’s especially important with new technologies…doubly so with Tesla products.

    We’ve got one guy here in the comments saying it was free and another quoting like $26k cost…

    Anyone know where there are actual real-world accounts total install cost and how it’s working out? I have my own hypothesis, given that they’ve been out for 5 years but aren’t really that common…

    Reply
  4. AvatarStephanie

    I am considering placing an order for the Tesla Solar Roof and the quote online recommends two Powerwalls, but nowhere does it say they are required. Silly question, will the Solar Roof not work without the Powerwalls? I am in Los Angeles, so I am wondering where to find more information regarding California reimbursing the charge for the batteries and installation as mentioned above. Any direction would be appreciated!

    Reply
    1. AvatarRigo Cisneros

      You can use it without a battery pack, but there are consequences. If you use solar to supplement your utilities, it is not an issue. You’ll need a professional to set you up safely so it can switch between the two power sources.

      Reply
  5. AvatarStanley Eng

    Is it better to use Tesla which took over solar City to install power wall battery or batteries to mesh with my solar city panels already installed on my roof, or can I use another contractor to install battery back up system?

    Reply
    1. AvatarJake Cosley

      You can use licensed contractors or other solar installation companies, and avoid the hassle of waiting for Tesla after failing inspection and experiencing customer service issues.

      Reply
  6. AvatarMark Anderson

    I ordered one Tesla powerwall ,..Tesla had thier guy come out and evaluate,.. the installation (which at the time had to be done by a Tesla certified installation company) total cost would be $26, 000.00 including labor and the battery. I already have solar panels and an inverter. And at the time the battery was $6,000.. I would also have to add 16 more panels to my system to keep the Tesla battery charged which is another $40,000 to feed the Tesla battery. So when you think of the cost of the battery the life of the battery and how much you pay to keep it charged is it really worth it?

    Reply
    1. AvatarDen

      For you, probably not, although your values seem weird.
      $40k for 16 panels of solar (about 5.7kwh) is $7 a kwh which is almost triple that of current prices.
      $20,000 for installation cost of a $6000 battery to an existing system is also weirdly expensive.

      I don’t think these values are typical for most customers. More typically — especially compared to what I paid – is that a Battery, plus gateway, plus installation, minus 26% federal incentives, leads to a payment of about $8000 total. Without the incentives its about $11k.

      For the most part the powerwall isn’t a pure financial decision. Financially it doesn’t pay for itself. If you get it, its for other reasons — the security of having a whole home UPS, the ability to save a little extra money by avoiding Time of Use rates, and of maximizing your net metering and minimizing reliance at night. If those things appeal then the cost is worth it, if they aren’t necessary then skip.

      Reply
    2. AvatarThomas Gardner

      Currently, we are paying upfront for three powerwalls ($34k) and the state of California will reimburse us for the charge for batteries and installation.

      Net cost, zero dollars

      Available battery power, 40.5kwh. The idea, during fire safety/power shutoff, we will have sufficient night time energy to run A/C and the rest of household needs. This coupled with a 12.5kW (39 panel/$42k) solar rooftop array.

      All the above backed up with a redundent generator from a big box store.

      Reply
      1. AvatarKB

        Thomas – My understanding is that the California SGIP rebate is for up to 10% of the cost of the battery only. SGIP does not include installation, permits, other fees etc. Is there some other CA incentive that I am not aware of?

      2. AvatarJulius Seizure

        I also live in California and would gladly pay zero dollars for three powerwalls. Can you tell me more about your reimbursement.

      3. AvatarHoward

        Our “Solar Company “ designed a system where the back up generator would run the house but would NOT charge the Tessla wall batteries. That just seems bizarre and it defeats the whole purpose for having a off-grid home. We had to do the research and change the specs of the generator. On the day they were supposed to show up there was no sign of them and when we finally got ahold of them they said that they had not received the batteries and had no idea when they would arrive. This is despite having a contract for almost a year and having a 50% deposit on the whole thing. I’m afraid that this is going to be a disaster….

      4. AvatarLinda Peckham

        The program for full rebate in CA has to fall under those properties that are in high fire zones that have had PSPS (power shut off events by the power companies to prevent equipment from starting fires during high winds) and rely on an electric pump for their water well. That is my understanding.

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