Adding Battery Backup To Existing Home Solar Panels

  • February 23, 2023
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Adding Battery Backup to an Existing Home Solar System

You’ve installed solar panels on your home, now you’re considering battery storage. Maybe you know someone with a solar battery, or you want to make your home more resilient to extreme weather. Whatever piqued your interest, you’ve come to the right spot.

It’s no secret that times are changing. Electricity prices are increasing, severe weather is becoming the norm and grid infrastructure is growing older as the demand for electricity escalates.

Adding battery backup to an existing solar system can help you protect your home and your loved ones against events that are beyond your control.


How Do Solar Panels and Battery Storage Work Together?

Your solar photovoltaic (PV) panels work by absorbing energy from the sun and turning it into an electrical current. That energy is then used in real time, powering your electric appliances when the sun is up. If you don’t use that energy, it would be wasted — this is one reason why net energy metering (NEM) is appealing.

In states that allow net metering, you can send any excess energy that you don’t use back to the grid and your utility will issue credits on your electric bill in return. Some utilities offer an attractive retail rate for this clean energy, others offer a small percentage and some offer nothing. As utilities strive to reduce their costs, many are pushing to cut net metering programs, as is the case in California, with the state’s recently approved NEM 3.0.

Any credit rate less than full retail makes a solar battery more financially appealing. By allowing you to store your own solar power and use it later on, a backup battery means you don’t have to send excess energy to the grid subject to the program offered by your utility for excess energy; you can use the power your system generated during the day.

Solar Home Battery Backup Power During a Grid Outage*

Real-time production also means if you have a home solar system without a battery, you will not have power during a power outage.

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 for safety. 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 from your system back onto the grid.

During an outage, your solar battery acts as a substitute for the grid. You’ll 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 as a solar-only system, a solar system with storage can operate independently of the grid.

Outsmart Time of Use Rates


In an effort to shift power consumption away from peak demand, new rate designs are gaining traction across the nation. Utilities in California, Massachusetts and Arizona, for example, have adopted time-of-use (TOU) rate plans, and more are piloting new rate structures. With a TOU plan, the price you pay for grid electricity varies based on the time of day and when demand is the highest.

For instance, PG&E, the nation’s largest utility company serving parts of California, applies peak TOU rates between 4 and 9 p.m. on weekdays. On these plans, electricity is most expensive in the early evening, when the sun is setting, and your solar production is waning for the day. However, the value of net metering credits is also greater during peak hours.

When you have a solar battery, you can program it to help you maximize net metering credits by using stored energy during peak hours and sending any excess power to the grid for maximum credits.

Even if you don’t have net metering policies in your state, a solar battery can prevent you from having to pull electricity from the grid during peak pricing to help keep your bill as low as possible.


Frequently Asked Questions About Adding Battery Backup to Existing Solar


When you choose Sunnova +SunSafe® add-on battery service, we offer several different options from leading manufacturers, from Tesla to Generac to Enphase to SolarEdge. The expected lifespan will depend on the product you choose. For instance, after 10 years, your Tesla Powerwall warranty guarantees that your battery will still retain 70% of its charging capacity*, so you can keep your battery for years to come.

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.

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.

During a grid outage, if you only have solar panels, you won’t have power. Adding battery storage to an existing solar system is the best way to use clean energy during an outage. Sunnova also offers standby generators, powered by natural gas, as an alternative (or in addition to) battery storage.

With Sunnova +SunSafe® add on-battery, the coverage for an add-on battery depends on the term of your agreement, whether it’s for 10, 15 or 25 years.

Ready to learn more? Each solar system is different, so the first step to adding battery backup is to speak with one of our solar experts. They can help you determine the best way to retrofit your solar system for better control over your energy independence.


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