Solar panels and batteries can do more than provide backup power during an outage. They can also help you use more of your own solar energy after sunset.
Imagine a sunny afternoon in California. Your solar panels are producing electricity, and then the neighborhood loses power. Will your lights stay on?
For a typical grid-connected solar system without backup equipment, the answer is no. The system shuts down when the grid goes out, even while the sun is shining. That prevents electricity from flowing onto utility lines while crews restore power.
What changes when you add a battery?
A properly designed solar and battery system can disconnect your home from the grid during an outage. The battery can then power the parts of your home connected to its backup system. When conditions allow, the panels can continue producing electricity during the day and help recharge the battery.
Having a battery does not automatically mean every appliance in the house will run. Your installer needs to know what you want to keep on and design the system around those needs.
Batteries are useful on ordinary nights, too
A battery does not have to wait for a blackout to help. During a normal day, your panels may produce more electricity than your home needs at that moment. A battery can store some of that excess solar energy for you to use in the evening or overnight, when the panels are no longer producing.
That can have a financial benefit, depending on your utility and billing plan. Some plans give you less credit for electricity sent to the grid than they charge when you buy electricity later. In that situation, storing solar energy and using it yourself after sunset may be more valuable than exporting it during the day and buying power back at night.
For example, California’s Net Billing Tariff pays for exported electricity based on its value to the grid at the time of export; it does not simply give a one-for-one retail credit. That makes the timing of your solar use an important part of the battery conversation. Utility rules differ, though, so a homeowner should compare the actual export credits and electricity rates on their own plan before assuming a battery will save a particular amount.
How long will a battery last during an outage?
That depends on how much usable energy it stores and how much electricity your home uses. Keeping a refrigerator, Wi-Fi, lights, and phone chargers running is a different job from running multiple air conditioners and an EV charger.
Sunlight matters as well. Solar production may help replenish the battery during a daytime outage. At night, you rely on the energy already stored. California’s Public Utilities Commission recommends understanding your battery’s limits and prioritizing the appliances you need most.
Two questions to ask before you choose a system
First: “If the grid goes down tonight, exactly what will still work in my house?”
Second: “On a normal day, how will this battery use my solar energy, and how does that compare with my utility’s export credits?”
The answers will tell you much more than the phrase “battery backup included.” Vibe Solar can help you look at both sides of the decision: the power you want during an outage and the solar energy you could use after sunset.
Sources: U.S. Department of Energy—Homeowner’s Guide to Solar, California Public Utilities Commission—Net Energy Metering and Net Billing, and CPUC—Public Safety Power Shutoff FAQs.
Check out our other blogs HERE!
