Estimate how long a solar battery will last based on battery capacity, amp-hours, voltage, load watts, depth of discharge, inverter efficiency, and reserve capacity. Use this calculator for solar battery backup, RV batteries, off-grid batteries, cabin batteries, and emergency power runtime estimates.
Battery kWh mode:
The calculator uses battery capacity in kWh, adjusts for usable capacity, then divides by load kW.
Amp-hour mode:
The calculator converts amp-hours and voltage into watt-hours, then estimates runtime.
Watt-hour mode:
The calculator converts watt-hours into kWh, applies efficiency and reserve settings, then estimates runtime.
Required battery mode:
The calculator estimates how much battery capacity is needed for a target runtime and load.
A solar battery runtime calculator helps estimate how long a battery may power appliances, critical loads, RV equipment, cabin loads, or backup circuits before needing to recharge.
It can help compare runtime hours, usable kWh, amp-hours, load watts, reserve capacity, inverter losses, recharge time, and battery cost.
Your result shows estimated battery runtime in hours and days, usable battery capacity, nominal battery capacity, amp-hours, required battery size for target runtime, reserve capacity, recharge days, peak load comparison, and estimated battery cost.
Convert the battery capacity to usable kWh, then divide by the load in kW. For example, 9 usable kWh running an 800-watt load is about 11.25 hours.
Multiply amp-hours by battery voltage to get watt-hours. Then divide by 1,000 to get kWh, adjust for usable capacity, and divide by load kW.
Usable capacity is reduced by depth of discharge limits, inverter losses, battery efficiency losses, and any reserve capacity you want to keep available.
Yes. Runtime is directly affected by load. A 2,000-watt load will drain the same battery much faster than a 500-watt load.
No. This is an estimate. Actual runtime can vary based on battery chemistry, temperature, battery age, inverter design, surge loads, wiring losses, discharge rate, manufacturer limits, and changing appliance usage.