In the 1980s, Bulgaria produced only about 35% of its energy needs. In 2000, net electricity generation was 39 billion kWh, of which 47.9% came from fossil fuels, 7.5% from hydropower, and 44.5% from nuclear energy. In the same year, consumption of electricity totaled 34.4 million kWh. Total installed capacity at the beginning of 2001 was 11.9 million kW. Lignite and brown coal are major sources (98%) for thermal power plants, which are located primarily in the coal-mining areas, including the Maritsa East Basin. The Maritsa East thermoelectric station has a capacity of about 650,000 kW.
In September 1974, Bulgaria's first nuclear power station—with a 440-MW reactor—opened at Kozloduy in the northwest. A second reactor was added in 1975, and a third and fourth in 1981 and 1982. The fifth and sixth reactors, each with a capacity of 1,000 MW, came online in 1988 and 1993, respectively. By 1994, nuclear plants supplied about 40% of Bulgaria's power. Until the two new reactors were added, continuous problems with the two oldest reactors had contributed to the decline of the country's overall electrical production.
Petroleum was discovered in the early 1950s in southern Dobruja (along the Black Sea), and in 1968 about 475,000 tons were produced; output subsequently declined to a low of 117,000 tons in 1976 and then rose to an estimated 1,000,000 tons in 1987, before falling to 45,000 tons in 1995. In 1998, production amounted to 1,000 barrels per day. Petroleum processing began in 1963. In September 1974, a Soviet-Bulgarian natural gas pipeline was opened with an annual carrying capacity of 5 million cu m (176.5 million cu ft). In 1991, Libya doubled its crude oil deliveries to Bulgaria to offset declining exports from the former USSR.
Coal is the most important mineral fuel, with lignite accounting for nearly 90% and brown coal for around 10%.