Heat rate
The fuel energy a thermal power plant consumes per kWh of electricity generated; the inverse of efficiency, usually in BTU/kWh or kJ/kWh.
The heat rate measures thermal plant efficiency the other way round: how much fuel heat is needed per unit of electricity. A lower heat rate is better. It is standard in the US power industry and in plant performance guarantees, and is the key input for fuel cost per MWh.
Heat rate (BTU/kWh) = 3,412 / η
Example: 6,400 BTU/kWh → 3,412 / 6,400 = 53.3% (HHV)
Fuel cost (USD/MWh) = heat rate (MMBtu/MWh) x fuel price (USD/MMBtu)
Typical full-load heat rates (US EIA, HHV basis):
- Modern CCGT: 6,200–6,800 BTU/kWh (50–55% HHV, 56–62% LHV)
- US gas combined-cycle fleet average: about 7,500 BTU/kWh
- Open-cycle gas turbines: 9,500–11,500 BTU/kWh
- Coal steam plants: 9,500–10,500 BTU/kWh (fleet average about 10,000; supercritical about 8,700)
- Nuclear: about 10,400 BTU/kWh thermal equivalent (33% efficiency)
Heat rates rise (worsen) at part load, during start-ups and at high ambient temperatures, which affects plants that cycle to balance variable renewables. Gross versus net output (after auxiliary consumption) and HHV versus LHV must be specified; see calorific value.
Related terms
All terms →- Calorific value (HHV / LHV)
The heat released by complete combustion of a unit quantity of fuel; the higher (gross) value includes condensation heat of water vapour, the lower (net) value excludes it.
- Combined-cycle gas turbine (CCGT)
A power plant that runs a gas turbine and uses its hot exhaust to raise steam for a second, steam turbine, reaching electrical efficiencies of 55–64%.
- MMBtu
One million British thermal units (1.05506 GJ, 293.07 kWh); the standard pricing unit for natural gas and LNG in the United States and Asia.
- BTU (British thermal unit)
A traditional unit of heat, approximately the energy needed to raise one pound of water by one degree Fahrenheit; 1 BTU (IT) = 1,055.06 J.
- Open-cycle gas turbine (OCGT)
A simple-cycle gas turbine that exhausts hot gas directly to the atmosphere, trading lower efficiency (33–42%) for fast start and low capital cost, used mainly for peaking.
- CHP (Combined Heat and Power)
Simultaneous generation of electricity and useful heat from one fuel input, reaching total efficiencies of 75–90% versus about 35–60% for power-only plants.