Estimate the appliances likely to run at the same time.
How this calculator works
The calculator starts from estimated simultaneous running load, adds a configurable safety factor and checks the largest likely motor or compressor surge. The result then rounds upward to a commonly available inverter capacity.
Check short-duration startup demand from motors and compressors.
Apply safety headroom and round upward to a practical inverter size.
Worked example
A practical planning scenario
A property with 5.9 kW of likely simultaneous load should not normally use a 6 kW inverter with no headroom. After allowances and surge review, a 10 kW hybrid unit may be the practical tier.
Frequently asked questions
Is inverter kVA the same as kW?+
Not always. Power factor affects conversion between kVA and usable kW. Confirm the actual continuous kW rating of any inverter you consider.
Can a larger inverter give longer backup?+
Not by itself. Backup duration mainly depends on usable battery energy and the load being powered.
Why does the calculator add headroom?+
Operating continuously at the limit leaves little room for startup events, temperature derating or future loads.