Thermodynamic efficiency (e) is defined as:

<math>e \equiv \frac{W}{Q}<math>

where

W is the absolute value of the work done in one thermodynamic cycle

Q is the absolute value of the change in heat done in one cycle

For heat engines, Sadi Carnot derived efficiency as a function of the temperature of its hot and cold reservoirs:

<math> e \equiv \frac{T_H - T_C}{T_H}<math>

sv:Verkningsgrad