Estimate the solar battery size needed for backup power, off-grid use, RV solar, cabins, sheds, or home energy storage. This calculator estimates usable battery capacity, required battery bank size, amp-hours, backup time, number of batteries, depth of discharge, inverter losses, and reserve capacity.
Daily use mode:
The calculator multiplies daily energy use by backup days, then adjusts for depth of discharge, inverter efficiency, battery efficiency, reserve capacity, and safety factor.
Load watts mode:
The calculator multiplies average watts by backup hours to estimate required kWh, then calculates the needed battery bank size.
Backup time mode:
Enter an existing battery capacity to estimate how many hours it may support your average load.
Battery count mode:
The calculator estimates how many batteries are needed based on the capacity of each battery and the required total battery size.
A solar battery size calculator helps estimate how much battery storage may be needed before buying batteries, designing an off-grid system, adding backup power, or comparing storage options.
It can help compare battery kWh, usable capacity, backup time, amp-hours, voltage, number of batteries, system losses, reserve capacity, and estimated cost.
Your result shows the estimated battery bank size needed in kWh, usable capacity, required amp-hours, number of batteries, backup time, total nominal capacity, total usable capacity, reserve capacity, and estimated battery system cost.
Estimate the energy you need in kWh, then divide by depth of discharge and system efficiency. Add reserve capacity or a safety factor if you want extra backup margin.
For one day of backup, start with your daily kWh use. A home using 10 kWh per day may need more than 10 kWh of nominal battery capacity after depth of discharge and efficiency losses are included.
Usable battery capacity is the amount of energy you can realistically use after accounting for depth of discharge and efficiency losses.
Multiply battery kWh by 1,000, then divide by battery voltage. For example, 10 kWh at 48 volts is about 208 amp-hours.
No. This is an estimate. Actual battery sizing can vary based on load type, surge loads, inverter rating, battery chemistry, temperature, depth of discharge, wiring losses, solar recharge, generator backup, and local electrical code.