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.
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.
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.
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:
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.
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.
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
- 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.
How much does the Tesla Powerwall cost?
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. Tesla lists the Powerwall at a cost of $6,500 alone, and puts supporting hardware costs at $1,100, bringing the price of just the Powerwall and its associated components to $7,600 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. That number includes the battery, an inverter, various other equipment costs, and estimated installation costs.
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.
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.