How much battery storage and backup time might this budget support?

How it works

Understand the estimate

Nominal kWh equals budget divided by assumed cost per nominal kWh. Multiply by usable fraction; divide usable kWh by average backed-up load for approximate hours.

Make it more accurate

Discharge losses, inverter limits, backup surge currents, chemistry and warranty rules affect achievable runtime.

These figures are examples based on editable inputs. They do not represent verified current rates, supplier prices or quotes.

Usable capacity and runtime are not the same

Battery labels often state nominal energy capacity. A depth-of-discharge setting, inverter efficiency and minimum reserve can reduce energy available to your appliances. Runtime is then determined by total simultaneous load, not by the battery alone.

Try the numbers: For a nominal 5 kWh battery limited to 80% usable discharge, roughly 4 kWh is available before inverter losses. At a continuous 0.5 kW load, the idealised run time would be eight hours; a 2 kW load reduces it to two hours.

Before relying on the estimate

High start-up loads and inverter limitations can cause an installation to shut down despite theoretical energy remaining. Check both kilowatt output and kilowatt-hour capacity.

For more detail, read our calculation and editorial standards. The current price and personal circumstances must come from you; we do not fetch or invent live supplier rates.