Thermal Efficiency Calculator

Heat pump

Thermal efficiency formula

Enter the THOT

Thermal Efficiency:

This thermal efficiency calculator calculates the efficiency of a heat engine.

The thermal efficiency is a dimensionless unit.

If you take formulas in thermodynamics, you can get that η= 1- (T COLD/THOT).

TCOLD usually represents the ambient temperature where the engine is located. This may just be the temperature outside in whatever environment the engine is at.

THOT represents the temperature that the engine is at, whether this is the temperature of hot steam entering the turbine of a steam power plant or the temperature at which fuel burns in an interal combustion engine.

TCOLD is fixed by the surrounding environment. So in the only way to increase thermal efficiency is to increase the THOT, or the temperature that the engine operates at.

Even though the goal is to increase the thermal efficiency as much as possible, a thermal efficiency near 100% is practically unattainable due to the fact that the ambient temperature will almost always surely be lower than the engine operating temperature. Thermal efficiency of automobile average between 30% and 50%.

When calculating the thermal efficiency, an absolute temperature unit must be used such as Kelvin. This calculator uses Kelvin as the base unit to make all calculations. If you choose Celsius or Fahrenheit, they are converted to Kelvin; and then the calculations are done based on Kelvin.

In order to convert Celsius to Kelvin, 273.15 is added to the Celsius value.

In order to convert Fahrenheit to Kelvin, the formula to do is, TemperatureKELVIN= (T(°F) + 459.67)× 5/9.


Calculate the thermal efficiency (COP) of a heating system in which the TCOLD value is 270K and the THOT value is 500K.

η=1 - (TCOLD/THOT)= 1 - (270K/500K)= 0.46

So the thermal efficiency is 0.46 in this case.

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