Size a battery around your appliances

Enter average watts and hours for each device. For cycling appliances, use average watts derived from measured energy over time. This tool checks energy only; it cannot verify startup or electrical compatibility.

What the result means

Capacity needed includes your chosen reserve. Runtime uses the average load across the longest entered usage period; actual timing and simultaneous use can differ. At very low loads, inverter overhead can make this simplified estimate optimistic.

Example: 100W for 8 hours, 85% usable energy and 10% reserve needs about 1,046Wh nominal. A 1,024Wh battery gives about 7.8 hours at the same 100W load. Neither figure is a measured result.