How long does a home backup battery last in an outage?
The honest answer is that it depends. Here is what it depends on, and how to estimate it for your home.
It comes down to two numbers
The first is how much energy is reserved in the battery for backup, measured in kilowatt hours (kWh). The second is how fast your home uses energy while the grid is down.
A simple estimate: hours of backup equals the kWh reserved, divided by the kWh your home uses each hour.
How much power homes use
According to the U.S. Energy Information Administration, the average home used 863 kWh a month in 2024. In Texas the average was 1,096 kWh a month, and in Illinois it was 693 kWh. [1]
For the average Texas home, that works out to about 36 kWh a day, or about 1.5 kWh an hour. For the average Illinois home, it is about 23 kWh a day. Averages include air conditioning and heating, so summer days in Texas usually run higher.
A worked example
These numbers are only an illustration, not a promise about any system. Say 10 kWh were reserved for backup, and the home kept using about 1.5 kWh an hour. That energy would last about six and a half hours.
If the household cut back to the essentials and used half as much, the same energy would last about twice as long. Solar panels can also recharge the battery during daylight, where solar is part of the system.
Ways to make your backup last longer
Set the thermostat a few degrees warmer in summer, or cooler in winter.
Hold off on big loads like the clothes dryer, oven, pool pump and EV charging until the grid is back.
Keep the fridge and freezer closed as much as you can.
Charge phones and laptops early, while the battery is full.
How the VirtuGrid program uses your battery
While the grid is up, the energy stored in your battery helps support the grid market. That grid work is how the program covers the battery and its installation. A reserve is kept for your backup.
When the grid goes down, your home switches to the energy reserved in your battery automatically. How long it lasts depends on the battery's charge and how much power your home uses.
VirtuGrid is an independent sales partner of SOLRITE. Licensed installers do the installation, and the program owns, monitors and maintains the equipment. Rates and terms are set in your agreement, which you review before you sign. See the details for Texas or Illinois.
Questions people ask
It depends on the battery, how it is connected to your electrical panel and how much power you use. Your advisor explains what your setup covers before you sign anything.
If your system includes solar panels, they can recharge the battery during daylight. Without solar, it recharges once the grid is back.
Your home is without power until the grid comes back or the battery recharges. Using less power stretches the time you have.
As with any backup system, don't rely on it for life support or critical medical equipment without a dedicated backup plan.
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