Build your load list
How the calculation works
Delivered energy is the sum of average watts × hours for all devices. Required nominal battery capacity = delivered energy ÷ delivery efficiency ÷ usable fraction. A 20% reserve means the usable fraction is 80%.
For example, 1,000Wh of load energy at 85% efficiency with 20% reserve requires about 1,471Wh nominal capacity. These percentages are adjustable assumptions.
Output and startup estimates
The calculator conservatively adds running watts for all listed devices. For startup, it assumes one device starts while the others are running, then reports the highest such combination. Multiple simultaneous starts may need more.
If you enter zero startup watts, the calculator treats the startup requirement as unknown. A compatibility warning remains visible. Surge duration, voltage and individual-port limits require a separate manual check.
Limits of the estimate
The runtime result assumes the listed energy pattern repeats over the longest device window. It is not an appliance simulation. Inverter standby draw, battery age, temperature and changing loads can shorten real runtime.
Use measured appliance energy when possible. This calculator cannot approve medical equipment, house wiring, motor compatibility or a solar array. Confirm those separately before purchasing.