The efficiency of a Carnot heat engine, known as the Carnot efficiency, is given by:
Where:
- is the efficiency of the Carnot engine (dimensionless),
- is the absolute temperature of the cold reservoir (in Kelvin, K),
- is the absolute temperature of the hot reservoir (in Kelvin, K).
The absolute temperature in Kelvin is used in this formula.
The Carnot efficiency represents the maximum possible efficiency for a heat engine operating between two given temperature reservoirs, assuming reversible processes and no energy losses.