Heat Pump Electrical Load Calculator

How to use this calculator

1. Enter the heat pump's heat output in kW (the thermal power it delivers).
2. Enter the COP — how many units of heat it gives per unit of electricity.
3. Pick the supply and click Calculate load for the electrical input, current and breaker.

How the electrical load is found

A heat pump's electrical input is its heat output divided by the COP; the current then follows from the supply:

The suggested breaker is the next standard rating above the running current. Heat pumps draw a higher inrush at start-up, so the manufacturer may specify a larger breaker or a soft starter.

Typical COP and what it means

COP falls in cold weather, so a unit rated COP 4 in mild conditions may give 2–2.5 at −10 °C, raising the electrical load.

Frequently asked questions

How much electricity does a heat pump use?

Divide the heat output by the COP. A 6 kW heat pump at COP 3.5 draws about 1.7 kW of electricity — roughly 7.5 A on a 230 V supply.

What breaker does a heat pump need?

Size it above the running current, but follow the data plate: inrush at start-up and defrost cycles often mean the maker specifies a larger breaker or a dedicated circuit.

Why does the load change with temperature?

COP drops as the outdoor temperature falls, so the same heat output needs more electrical input on the coldest days — exactly when demand is highest.