Heat Pump COP Calculator

About this calculator

The coefficient of performance (COP) of a heat pump measures how much heat energy it moves per unit of electrical energy consumed — a COP of 4 means 4 units of heat delivered for every 1 unit of electricity used. The ideal, theoretical maximum is the Carnot COP, set by thermodynamics alone: for heating, COP_heating = T_hot / (T_hot − T_cold), and for cooling, COP_cooling = T_cold / (T_hot − T_cold), with both temperatures in Kelvin — no real machine can exceed this limit.

HVAC engineers and energy analysts use the Carnot COP as a theoretical benchmark against which real heat pump efficiency is measured (real units typically achieve 40–60% of the Carnot value), and it explains why heat pumps become less efficient in very cold climates — as the outdoor-indoor temperature gap widens, the Carnot ceiling drops, so there's less heat to extract per unit of work. Enter the hot and cold reservoir temperatures to find the ideal COP.