Generator Capacity Calculator

About this calculator

Sizing a backup generator directly off total connected load badly oversizes the unit, because not every connected appliance or circuit runs simultaneously at full draw, and generators are rated in kVA (apparent power), not the kW (real power) figure connected load is usually specified in. This calculator multiplies your total connected load by a diversity or demand factor, the realistic fraction of connected load actually drawn at once, then divides by a power factor to convert from real power to the apparent power (kVA) rating generators are sold by. Enter connected load, an appropriate diversity factor and power factor, and get a right-sized generator recommendation instead of over-provisioning based on total nameplate load alone. Because diversity factor depends heavily on what's actually connected, a building with many simultaneous heavy loads needs a higher diversity factor than one with occasional intermittent use, use a factor grounded in your actual load profile rather than a generic default for a dependable sizing result.

Frequently asked questions