Home Solar Battery Sizing Calculator
Sizing a home battery backup system means balancing your daily critical load against how many hours you want to stay powered. Enter your load and backup duration to estimate the battery capacity you need.
Required Battery Capacity
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Critical Load Per Hour (kWh)—
Total Energy Needed (kWh)—
Battery Capacity After Losses (kWh)—
About this calculator
Estimate the battery capacity needed to back up your essential home appliances during an outage based on daily energy usage and desired backup hours.
Frequently Asked Questions
What counts as a critical load?
Critical loads typically include refrigerators, lighting, medical equipment, well pumps, and internet/routers — not full HVAC or large appliances.
Why does depth of discharge matter?
Most batteries shouldn't be fully drained to protect longevity, so usable capacity is less than the rated capacity.
Should I size for more than my critical loads?
If you want to run more appliances during an outage, increase the critical load percentage or add another battery module.