Estimate how much solar battery backup you need for outages, critical loads, whole-home backup, RV backup, cabin backup, or off-grid power. This calculator estimates backup runtime, required battery size, usable battery capacity, batteries needed, solar recharge time, load coverage, and estimated battery backup cost.
Runtime mode:
The calculator estimates how long an existing battery bank can power your average backup load.
Required size mode:
The calculator estimates the battery size needed to run a load for a target outage length.
Critical loads mode:
The calculator estimates battery backup needs from daily critical-load energy use and backup days.
Solar recharge mode:
The calculator estimates how much solar energy can recharge the battery per day and how long recharge may take.
A solar battery backup calculator helps estimate how much storage is needed before buying batteries, adding backup power, or designing a solar-plus-storage system.
It can help compare backup hours, usable battery capacity, battery count, reserve capacity, critical load coverage, solar recharge time, peak load, and estimated backup cost.
Your result shows estimated backup runtime, usable battery capacity, required battery bank size, number of batteries, amp-hours, solar recharge per day, estimated recharge time, peak load coverage, reserve capacity, and estimated battery backup cost.
Divide usable battery capacity by average backup load. For example, a 10 kWh usable battery running a 1 kW load may last about 10 hours.
Multiply your average load by the outage hours you want to cover, then adjust for depth of discharge, inverter efficiency, and reserve capacity.
Critical load backup powers only essential circuits such as refrigerator, lights, internet, sump pump, medical equipment, or selected outlets instead of the entire home.
They may, if the system is designed for solar charging during outages. Recharge depends on solar array size, sunlight, inverter design, battery state of charge, and system settings.
No. This is an estimate. Actual backup runtime can vary based on battery age, temperature, load changes, inverter limits, surge loads, battery chemistry, wiring losses, weather, solar recharge, and manufacturer settings.