No real engine can beat the Carnot limit, which is why power plants aim for very high steam temperatures.
How to use the Carnot Efficiency Calculator
- Hot reservoir temperature
- Cold reservoir temperature
Results update as you type, and every field accepts the units shown in its menu.
How it works
Convert both temperatures to kelvin and subtract their ratio from one.
Inputs explained
| Field | What to enter |
|---|---|
| Hot reservoir temperature | Units: K, °C, °F |
| Cold reservoir temperature | Units: K, °C, °F |
What each result means
- Maximum efficiency = (1 – [Cold reservoir temperature]÷[Hot reservoir temperature]) × 100
- Carnot COP (heat pump) = [Hot reservoir temperature] ÷ ([Hot reservoir temperature] – [Cold reservoir temperature])
Example values
How the main result changes when Hot reservoir temperature changes and everything else stays at the example values above:
| Hot reservoir temperature (K) | Maximum efficiency (%) |
|---|---|
| 436.58 | 30.56 |
| 654.86 | 53.71 |
| 873.15 | 65.28 |
| 1,091.44 | 72.22 |
| 1,309.73 | 76.85 |
| 1,746.3 | 82.64 |
Formula
η = 1 − T_c ÷ T_hWorked example
Inputs — Hot reservoir temperature: 873.15 K; Cold reservoir temperature: 303.15 K.
Results — Maximum efficiency = 65.28 %; Carnot COP (heat pump) = 1.532.
Frequently asked questions
Why use kelvin?
The formula needs absolute temperature.
How efficient are real power plants?
Typically 33–45% for steam plants and up to about 60% for combined-cycle gas plants.
What formula does the Carnot Efficiency Calculator use?
η = 1 − T_c ÷ T_h.