Fellside Power Station is a 168 MWe CHP gas-fired power station adjacent to the Sellafield site, which it supplies with process and heating steam. It is run as Fellside Heat and Power Ltd, is wholly owned by Sellafield Ltd and is operated & managed by PX Ltd. It was built in 1993, in anticipation of the closure of the Calder Hall generating station, which supplied these services.

The station uses three General Electric Frame 6001B gas turbines, with power entering the National Grid via a 132 kV transformer. The turbines at Fellside are normally natural gas fired but are also able to run on distillate (diesel) fuel.

In May 2023, Sellafield Ltd removed a set of large, now redundant steel tanks at the Fellside power station. Their original purpose has been fulfilled by newer tanks.