Calculators

Convert apparent power in kilovolt-amperes (kVA) to real power in kilowatts (kW) using the load’s power factor. The default power factor is an illustrative assumption; use the equipment’s rated power factor when available.

Calculate real power from current and voltage for DC, single-phase AC, or balanced three-phase AC. Enter power factor as 1 for DC or a resistive AC load. For three-phase AC, enter line-to-line voltage and line current. Defaults are illustrative.

Estimate current from real power, voltage, power factor, and electrical system type. For DC, set power factor to 1. For three-phase AC, enter line-to-line voltage; the calculation assumes a balanced load. Defaults are illustrative.

Estimate generator running costs from fuel consumption, operating time, fuel price, and an optional hourly maintenance allowance. Defaults are illustrative; fuel consumption varies with load and generator specifications.

Estimate generator runtime from usable fuel and the generator’s fuel consumption rate at your expected load. Use a manufacturer-rated or measured consumption rate for that load; actual runtime varies with load and operating conditions. Defaults are illustrative.

Estimate fuel used by identical generators from their fuel consumption rate at the actual operating load and their running time. Use a manufacturer rating or measured rate for the expected load; fuel use varies with load and conditions. Defaults are illustrative.

Estimate generator capacity from the total running load and the largest additional starting surge. Enter the starting and running watts for the same appliance, and assume appliances start one at a time. Defaults are illustrative; check appliance labels and generator ratings.

Estimate generator capacity from the appliances you expect to run together, the largest additional starting surge, and a reserve margin. Add the running watts of all simultaneous loads. Enter the largest starting surge above its running watts, rather than the appliance’s total starting watts. Choose a generator with sufficient running and starting ratings; round up to an available size.