In 2001, Laos had a total installed electrical generating capacity of 425,000 kW, up from 225,000 kW in 1988. Production of electricity in 2000 totaled 1,000 million kWh (up from 532 million in 1988), of which 98% was hydropower and the remainder from conventional thermal sources. Consumption of electricity in 2000 was 690.6 million kWh. The nation has an estimated hydroelectric potential of 12,500,000 kW, most of which is undeveloped. The largest power project is the Nam Ngum Dam, located on the Mekong 72 km (45 mi) from Vientiane. Construction began in 1969, with the first stage completed in 1971 and the second stage in 1978. Annual output at Nam Ngum is around 900 million kWh, with about 90% of the electricity produced being supplied to Thailand. An additional 3,000 kW of capacity comes from several smaller hydroelectric facilities, and about 14,000 kW is provided by diesel-powered generators throughout Laos.