Tesla Powerwall Review: A Well-Rounded Solar Battery
The Tesla Powerwall has a few strengths and no glaring weaknesses. And it comes at a reasonable price for a solar battery.
Sarah DroletAssociate Writer
Sarah Drolet is an associate writer at CNET covering home energy, residential solar power and emerging energy technology. She previously wrote about home and moving-related topics for MYMOVE. Sarah graduated from Coastal Carolina University with a bachelor's degree in communications.
Electricity rates are rising, and some states are decreasing how much homeowners with solar panels get compensated for selling their excess energy to the power grid. If you face frequent power outages, fear higher power bills or want to use your excess solar power, you might want to consider a home battery backup. During your solar battery search, you'll probably encounter the Tesla Powerwall.
Tesla, mostly known for its electric vehicles, has made a name for itself in the solar industry too, especially since acquiring SolarCity in 2016. Tesla introduced the Powerwall in 2015, but didn't start mass production of the battery until 2017.
The battery we're reviewing in this article is the Tesla Powerwall 2, but we're referring to it just as the "Powerwall" since the original Tesla Powerwall is no longer available. The Powerwall is interesting because it's just so average, and strangely enough, we mean that in a good way. This battery is on par with its competition in almost every way. There are a few stand-outs: Its unlimited-cycle warranty, capacity stackability and some interesting app features are noteworthy. But other than that, the Powerwall doesn't stand out from the battery crowd too much. Nor does it have any particular glaring weaknesses.
This review is based on specs and information provided by Tesla online. Tesla does not have a media relations department, but they do have a general press email. After emailing this contact, we received no response.
Here's what you should know about the Tesla Powerwall.
What do I get with the Tesla Powerwall?
The Tesla Powerwall is one of the most well-rounded lithium-ion batteries available. In our review of solar batteries, this battery got at least an average rating in just about every category. It's a good value battery option because it tends to be a bit cheaper than its competitors. Here are the Tesla Powerwall's specs at a glance.
Tesla Powerwall specs
How many can I stack?
Up to 10
Depth of discharge
Peak power output (on-grid)
Continuous power output (on-grid)
$9,000 - $13,000
Tesla has two battery options: the Tesla Powerwall and Tesla Powerwall Plus. The batteries are pretty similar to one another -- the difference is how they interact with your home's energy system. The Powerwall is compatible with new and existing solar panel systems. It can also work as a stand-alone home battery without solar panels. On the other hand, the Powerwall Plus battery is integrated with a Tesla Solar Inverter and must be installed with solar panels. Both Tesla batteries can be installed with other brands of solar panels. You don't needTesla solar panels to install a Powerwall.
Both Tesla batteries have a 13.5 kilowatt-hour energy capacity, a decent size for a home battery backup. However, if you have a larger home (or plan on going off-grid), you'll likely need multiple Powerwalls. One Tesla Powerwall is ideal for partial home backup, while whole-home backup will likely require two or more Powerwalls. You can install up to 10 Powerwalls for a total of 135 kWh of energy storage. The Tesla Powerwall is not as modular as other batteries on the market, making size upgrades a bit difficult (and expensive). If you find yourself needing a capacity upgrade, you'll have to buy another 13.5 kWh battery.
Performance and efficiency
Efficiency-wise, the Powerwall is about average for the batteries we examined. The Powerwall's round-trip efficiency is 90%, meaning 10% of the electricity gets lost on its way to the battery for storage. A round-trip efficiency of 90% (or higher) is pretty standard for lithium-ion batteries. The Tesla Powerwall's depth of discharge (how much of the battery you can use at once without damaging it) is slightly higher than average at 96%. However, just because you can drain the majority of your battery all at once doesn't mean you should. One of the main factors affecting a battery's lifespan is the number of cycles it goes through. A battery cycle is the process of discharging (emptying) your battery and then recharging it. In other words, the fewer times you fully cycle your battery, the better.
What about power output? It's pretty good. One Powerwall can output a peak of 7 kilowatts, with continuous power output of 5 kW. A battery's peak power output is the amount of power the battery can put out all at once without damaging anything. Peak power output is typically used when activating large loads or appliances, such as when your AC or heat kicks on. Continuous power output is the amount of power the battery is able to put out at all times. The more Powerwalls you install, the higher the power output. The Tesla Powerwall and Powerwall Plus have the same on-grid power output capabilities, but the Powerwall Plus has far better backup power output capabilities, with a peak power output rating of 22 kW in full sun or 10 kW with no sun and a continuous power output rating of 9.6 kW in full sun or 7 kW with no sun. The Tesla Powerwall can also be installed to a system with a backup generator, but it will need to be connected with an external automatic or manual transfer switch.
Tesla's online customer service reputation is not the best, and it seems easier to find bad customer service reviews than good ones. Tesla Solar is not Better Business Bureau accredited, but anecdotal evidence suggests poor customer service and some customers even regretting their purchases. There are frequent complaints about rude customer service or sales representatives, as well as Tesla not following through when it comes to communicating with their customers.
The Powerwall's warranty stands out among competitors. Here's what it includes:
70% end-of-warranty capacity guarantee
A 10-year warranty is the industry standard for solar batteries, but few come with unlimited cycles. The typical battery warranty covers 4,000 to 6,000 cycles, making Tesla's unlimited-cycle warranty more competitive. The number of times you cycle your battery (drain and recharge it) affects its lifespan, which is why many manufacturers will include a cycle or throughput clause in their warranty.
The Powerwall's warranty also comes with a 70% end-of-warranty capacity guarantee. Batteries lose capacity and their ability to hold a charge over time, so some manufacturers will include an end-of-warranty capacity guarantee. This is the manufacturer's guarantee that your battery will be able to store a specific percentage amount of energy by the time your warranty period is up. Tesla guarantees the Powerwall will retain at least 70% of its original capacity by the time your warranty ends.
Using the Tesla app, you'll be able to view and monitor your home's energy usage, as well as analyze and compare data about your home's past and current energy production. Powerwall can also be customized to help support your energy goals by utilizing the different control mode settings through the app. These settings essentially change how your battery charges and discharges. Keep in mind that some features and settings are only available when paired with solar panels.
You can also set a designated percentage of your Powerwall's capacity aside to be reserved for backup power in the event of grid outages. When using the backup reserve setting, Tesla recommends setting a backup reserve of 20%. However, you can set it to whatever you like.
The Tesla app is not without its flaws. Online reviews show complaints about frequent glitches and the unreliability of the app, with some users saying it only seems to work half the time they use it.
Tesla Powerwall vs. Tesla Powerwall Plus
There isn't much of a difference between the Powerwall and Powerwall Plus. The Tesla Powerwall is just a battery, and can be installed with or without solar panels. The Tesla Powerwall Plus is a regular Tesla Powerwall battery that has been integrated with a Tesla Solar Inverter. The Powerwall Plus is designed specifically for solar installations, while the regular Powerwall model is compatible with or without solar panels.
Both batteries have the same capacity (13.5 kWh). However, the Powerwall Plus has a much higher backup power output rating, making it a better option if you are installing a new system and have plans to go completely or partially off the power grid. Most homes will likely need more than one Tesla battery (of any model) to live completely off-grid. Both Tesla batteries are interchangeable, meaning you can install a mix of up to 10 Powerwall and Powerwall Plus batteries.
How much does the Tesla Powerwall cost?
Home battery systems are not cheap. The Tesla Powerwall generally costs between $9,000 to $13,000. Pricing depends on your location and other installation and labor costs. The Powerwall tends to be cheaper than similar competing batteries. When it comes to batteries, you can generally expect to pay between $1,000 and $2,000 per kWh of energy storage.
To get the most accurate pricing information, talk to a Tesla-certified installer in your area, and get multiple quotes to get the best price possible. Gathering a mix of quotes from national and local installers is the way to go.
Is the Tesla Powerwall my best choice?
The Powerwall is a very well-rounded battery in its capacity, performance and efficiency. Is it a decent battery? Yes. Is it your best choice? It depends. The best battery for your home is one that fits your household's energy needs and what you are looking to accomplish with a battery installation. Most installers offer more than one brand of battery, so explore other battery options from installers in your area if you can. And try to get multiple quotes to get the best price possible.
How we evaluated the best solar batteries
Not every battery is right for every home. It's difficult to pinpoint exactly which solar battery is the "best" battery for your home without doing an on-site inspection. We're unable to do hands-on testing with solar batteries because of the complexity of solar panel systems, but there are ways to evaluate and compare these batteries. Here's how we evaluate solar batteries.
First, we created categories that would be used to evaluate the battery's efficiency, performance, capacity and value. We also weighted each category. The weight of each category reflects the importance we felt was relevant to the average consumer. Here are the categories we considered and their weights:
Battery modularity (stackability): 20%
Round-trip efficiency: 15%
Depth of discharge: 10%
Power output: 10%
Customer reviews: 10%
Battery capacity: 5%
We looked at 15 of the most common batteries on the market and collected the data for each category to compare the numbers. Each category (for every battery) was then given a tier-style rating (from 1 to 5) to see which aspects of each battery were above average (among those on our list), average or below average.
Yes, but you would likely need multiple Powerwalls to go completely off the power grid. If you're installing a new solar system and have plans to go off-grid, consider installing the Powerwall Plus, which has a higher backup power output and was solely designed for solar purposes. However, you will likely still need multiple Powerwall Plus batteries to truly go off-grid.
Is the Tesla Powerwall eligible for the federal solar tax credit?
You can order a Powerwall online through Tesla or find an installer in your area that installs Powerwalls. If you order your Powerwall online and are located at a Tesla-serviceable address, Tesla will bring the Powerwall to your home and install it for you. If you are not at a Tesla-serviceable address, your installation will go through a Tesla-certified installer in your area.
What is the energy storage capacity of the Tesla Powerwall?
The Tesla Powerwall has 13.5 kWh of usable capacity. This is a decent size for a singular battery, but if you are looking for whole-home backup, you'll need multiple Powerwalls. You can install up to 10 Powerwalls for a total of 135 kWh. The Powerwall and Powerwall Plus batteries can be installed together.