When constructed it was the largest and most powerful coal-fired station in Europe, and it is still the second largest, after Drax in Yorkshire, England. It is a regional landmark, dominating the Forth skyline with its 183 m (600 feet) chimney stack. Like all other power stations in Scotland it lacks cooling towers, relying instead on river water as a coolant.

Longannet has an installed capacity of 2,400 MW (equivalent to 2 AGR nuclear stations) made up from four 600 MWe generation units, each featuring a single boiler feeding two 300 MWe GEC turbo-alternators, with the steam spaces cross coupled. The declared net capacity is rated at 2,304 MW due to operational losses. On average Longannet produces 10.4 TWh per year and in 2000-2001 achieved the highest generation output in its history by supplying more than 12.25 TWh to the National Grid.