Heat Rate Formula

Heat Rate

The heat rate is defined as the total amount of energy required to produce one kilowatt-hour (kWh) of electricity by an electric generator or power plant.
It is the input rate required for generating unit power. The heat rate can also be described as the ratio of thermal inputs to electrical output. The lower the heat rate higher the efficiency. In thermal generating system, incoming and outgoing energy typically exist in the same value or unit. The heat amount is proportional to the input of chemical energy divided by the liberated electrical energy.
The formula of heat rate is 

Rh = Ws × c × ΔT


Rh is heat rate in btu/hr,

Ws is steam flow in lb/hr,

c = specific heat capacity in btu/lb F,

ΔT is the temperature difference in F.

Solved Example

Example 1: Calculate the heat rate if steam enters a turbine at 400oF at atmospheric pressure and leaves the turbine at 200oF. Steam at 500 lb flows through the turbine each hour during normal operation.


Given parameters are,

Ws = 500 lbs/hr

c = 0.48

Tin = 400oF

Tout = 200oF

ΔT = 400 – 200

ΔT = 200oF

We have the Formula,

Rh = Ws × c ×ΔT

 Rh = 500 × 0.48 × 200

Therefore,  Rh = 48000 btu/hr

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