Backup Power Math: size your home backup before you buy
Backup power products are sold by capacity, output and surge. Those three numbers decide whether a battery will run your refrigerator, your well pump or your air conditioner. Our tools work them out from the appliances you actually own.
Tools
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Home battery backup calculator
Pick your appliances, outage length and solar. Get the battery capacity, continuous output and surge you need, then see which products meet all three.
How the numbers work
Each tool shows its working. You can edit the appliance watts and hours, the outage length, the solar size and the peak sun hours. Fixed assumptions, such as 90% depth of discharge and 90% inverter efficiency, are stated on the page but cannot be changed. Typical appliance watts are starting points, not promises, so check your own labels.
What we do not do
We do not install equipment, and nothing here replaces a licensed electrician. A licensed electrician should confirm any panel, transfer switch or 240 V work. Some links on this site are affiliate links, explained below and on the About page.