Home Power Battery
Backup FAQ

The most common home power battery backup & Tesla Powerwall Questions.

We talk to people daily about securing their home power battery backup with a Tesla Powerwall systems, and we hope our FAQ will answer your questions too.

Behind the Powerwall’s sleek, minimalist white casing is one of the highest density residential and light commercial AC battery storage solutions on the market. Backed by the Tesla name, the Powerwall 2 is a 13.5kWh capacity rechargeable lithium-ion battery that boasts 7kW peak and 5kW continuous power.

At roughly 45 inches tall, 30 inches wide, and 6 inches deep, the Powerwall 2’s compact profile combined with floor and wall mount options that can be installed inside or outdoors means you don’t have to sacrifice a ton of space for more storage.

What does a Tesla Powerwall Battery do?

Just like any other battery storage option, a Tesla Powerwall captures and stores energy to be used by your home when needed later. What makes the Powerwall standout from other battery storage options is its ability to power larger loads and for a longer duration. This means you have the freedom to power up more of what you need without running out of storage during an outage.

How does a Powerwall Battery Work?

In basic terms, sunlight is captured by your solar panels then converted into energy that you can use for your home. As that energy flows into your house, it is used by your appliances and any excess energy is stored in the Powerwall. Once the Powerwall is fully charged, additional electricity your system generates on top of that is sent back to the grid. When the sun goes down and your solar panels are not producing energy, your Powerwall will provide electricity to power your home.

Does a Powerwall need to be installed with solar?

Not technically, but it’s hard to see the benefit of having battery storage that’s not connected to a solar system in Washington State. Unlike areas that have a high variation in on-peak and off-peak rates, think California, time-of-use load shifting isn’t financially rewarding in the Evergreen State. There is no need to store your unused solar energy since net metering allows you to store your excess production on the grid as a credit to use later. This is essentially a free energy storage vault.

Battery backup systems that are connected to a solar system are eligible for the 26% Federal Solar Investment Tax Credit. Beginning in 2021, this tax credit will step down to 22% until a full sunset in 2022. Now’s a great time to lock in your energy rate before it rises again and the incentives disappear.

What can you power with a Tesla Powerwall?

It’s all about the give and take when it comes to planning out your home battery storage solution. When designing your energy storage system, it is essential to find a balance between the total capacity of the Powerwall(s) with the demand of everything you need to power up. Each Powerwall can deliver up to 21 amps, and up to 6 Powerwalls can be stacked together. However, even if there is enough amperage to cover all of your loads, we need to consider the pace of how quickly electricity will be drawn to maximize the effectiveness of your back-up system.

A common misconception is that your solar output will recharge your battery at the same rate you’re using it. This depends greatly on uncontrollable factors like weather and user consumption habits. An easy way to look at battery storage is to think of how driving tendencies vary by operator and by vehicle. You may be a more efficient driver of your new Prius while your cousin Karen drives a 2001 Jeep Wrangler like she’s running a desert race. Similarly, Powerwall performance will be dependent on user consumption tendencies and what you are powering up. A small, highly efficient home with energy efficient appliances might power more than a larger, older home with leaky windows. By monitoring your usage and storage abilities, you’ll gain greater insight into what you can power and how quickly your Powerwall might recharge.

Ultimately, to determine what’s best for you, we need to take a look at your average historic usage and discuss what you’re looking to get out of our battery storage.

Do I need more than one Powerwall?

We’re seriously not trying to dodge this question, but it really is different on a site-to-site basis and from a personal preference. For most systems, we install 1 or 2 powerwalls. The total number is a personal choice depending on how much power you want or need to store and what types of devices you hope to switch on during a grid outage. Each of our systems are fully customized to maximize the homeowner’s financial benefit and to reach their goals. To get a full picture of how many powerwalls you might need, we would need to have an in-depth conversation about your objectives and review your average consumption history.

How long does a Tesla Powerwall battery last on one charge?

It depends on what you use. Let’s just say you won’t be blasting your electric heating if the power goes off at night. A more realistic assumption for one Powerwall would be to run ten 100 watt light bulbs for 12 hours (without recharging the battery).

How many hours does it take to charge a Powerwall with solar?

This is another question that’s hard to quantify. How long it takes to charge a Powerwall with solar really depends on the weather, seasonal day lengths, brightness and shading. In perfect conditions with no loads and 7.6kW of solar power, a Powerwall could charge in 2 hours. Whereas for a typical December week up to 3 full days. Visit our main Powerwall page for how much longer solar will make a Powerwall last during an outage.

Does a Powerwall automatically switch on when the grid fails?

Your Powerwall will operate in a grid failure and your home will automatically switch over to the batteries. If the sun is shining when the grid goes down, your solar system will continue to charge your batteries and stop sending any energy back to the grid. We are required by code to install a “gateway” unit that relays power from your system to the Powerwall and isolates all the power in the house from the grid. This ensures the safety of lineworkers and is an automatic process when the grid goes out.

How much does a Tesla Powerwall cost?

A one unit Powerwall system can run from $12,500 to $13,000 depending on the degree of electrical difficulty. location on the building and if you purchase with solar. Multiple unit systems come with a significant savings, a two unit system can run from $20,500 to $23,500. Visit our financing page for our $0 down low interest loan options. Don’t forget, now is the best time to go solar with battery storage before the federal tax credit starts to fade away in 2021 and disappears in 2022. This incentive is also only eligible for Powerwall systems if they are connected to a solar system.

What type of warranty does a Tesla Powerwall have?

The standard Tesla Powerwall warranty is 10 years at 70% capacity. This means, if the Powerwall loses more than 30% of its storage capacity within 10 years it would be covered by the warranty.

What Incentives are available for battery backup systems?

Tesla Powerwall systems that are connected to a solar system are eligible for the 26% Federal Solar Investment Tax Credit. Beginning in 2021, this tax credit will step down to 22% until a full sunset in 2022.

Battery backup systems are exempt for all sales taxes. Visit our incentives page for more detaile information.

Now’s a great time to lock in your energy rate before it rises again and the incentives disappear.