Adding Battery Backup To An Existing Home Solar System 

battery storage for existing solar panels

Adding battery storage for existing solar panels enables a variety of benefits:

Solar Home Battery Backup Power During a Grid Outage1

Unlike a solar-only system, with a solar plus battery storage system, you can continue to produce and use your solar energy even when the grid is down. If you have a home solar system without a battery, you will not have power during a power outage.

Your home solar system has a constant relationship with the grid: when the grid is up, you can pull electricity from the grid during time of low solar production (at night, on cloudy days), and you can push excess solar production to the grid if you have net metering.

All grid-tied home solar systems are required by law to have an automatic shutoff switch that turns off your home solar system when the grid goes down. This is because of the connection between your home solar system and the grid - if utility workers are repairing damaged poles and wires, there cannot be any electricity flowing onto the grid. The automatic shutoff switch prevents your home solar system from sending energy back to the grid during an outage.

During a grid outage, your solar battery acts as a substitute for the grid – you will be able to push your excess solar production to charge your solar battery and pull energy from the battery to power your critical loads. Even though solar storage systems have the same automatic shutoff switch, a solar storage system can operate independently of the grid.

Maximize Your Economic Benefit

If you have a Sunnova +SunSafe® battery, we will automatically configure your solar battery to make sure you maximize the economic benefit on your solar investment.2

Traditionally, your excess energy production is transported back into the grid through net metering, which can offset your grid electricity consumption costs. However, with changing net metering policies and the rising costs of grid electricity, more homeowners are battery storage for existing solar panels to take advantage of as much of their solar energy as possible.

Outsmart Time of Use Rates

For solar homeowners in California and Arizona, time-of-use (TOU) rate plans are the new norm. With a TOU rate plan, the price you pay for grid electricity varies based on the time of day.

On a TOU rate plan, electricity is most expensive in the early evening, when the sun is setting and your solar production is waning for the day. For example, SDG&E defines peak hours as 4-9 p.m. However, the value of net metering credits is greater during peak hours.

If you’re a Sunnova customer, your battery will be configured to help you maximize your net metering credits. During peak hours, your home will run off of your battery. Any excess energy stored in your battery will be sent back to the grid for maximum net metering credits. Learn more about TOU rates here.

What is a Solar Battery?

Throughout the day, your home solar system is constantly converting the sun’s rays into energy to power your home. What happens when your home solar system produces more energy than your home needs?

A solar battery does exactly what its name suggests – it captures excess solar production for later use. Depending on your battery configuration, you may be able to pull energy from your solar battery at night, on low-production days, and during grid outages.

Frequently Asked Questions About Adding Battery Backup To Existing Solar

What is the lifespan of a solar battery?

Our Sunnova +SunSafe® add-on battery is a Tesla Powerwall. After 10 years, your Tesla Powerwall warranty guarantees that your battery will still retain 70% of its charging capacity3, so you can keep your battery for years to come.

Where do you install the solar battery?

We recommend you install your battery in a place away from direct sunlight or heavy rain. If possible, we will install in a garage or carport. The battery will be mounted to your wall above the ground.

How do I know if I need more than one solar battery?

If your home solar system is larger than 7.6kW with a single inverter, we recommend installing two batteries to store all of the energy your home solar system is producing.

How will I know if my solar battery is working?

After installation, we monitor your battery 24/7 to make sure it’s working. We also set you up with monitoring so you can check on your battery performance at any time.

Hassle-Free Battery Storage with Sunnova +SunSafe®

During a grid outage, if you do not have a battery, you will not have power. Adding battery storage for existing solar panels is the best way to complete your home solar system and move towards greater energy control and independence.

With Sunnova +SunSafe®, for parts covered under the 10-year manufacturer’s warranty, Sunnova will coordinate all maintenance and repairs, from start to finish.4 We offer a comprehensive installation service, including taking care of any permits you may need.

Depending on your state and utility, you may be eligible for a variety of incentives. For more information about local incentives and financing, schedule a call with one of our solar experts!



1. The amount of power available from the battery during a power outage is limited, depending on the loads connected, customer usage and battery configuration (i.e. batteries in certain areas may be set up to provide you with the best economic benefit, which may affect the amount of back-up power available). Solar systems and/or batteries may require repairs after weather events and such repairs may be delayed due to forces outside of our control. No assurances can be given that the solar system or the battery will always work. You should never rely upon either of these to power life support or other medical devices.
2. Your battery will be configured to provide the best economic benefit to you based on the utility information provided and in accordance with local state laws.
3. Tesla Powerwall warranty
4. Refer to the Warranty Agreement for complete warranty terms and limitations. Labor and/or battery replacement costs are not included.