Russia is the fourth largest generator and consumer of electricity in the world. Its 440 power stations have a combined installed generation capacity of 220 GW. Russia has a single synchronous electrical grid encompassing much of the country. The Russian electric grid links over 3,200,000 kilometres (2,000,000 mi) of power lines, 150,000 kilometres (93,000 mi) of which are high voltage cables over 220 kV. Electricity generation is based largely on gas (46%), coal (18%), hydro (18%), and nuclear (17%) power. 60% of thermal generation (gas and coal) is from combined heat and power plants. Russia operates 31 nuclear power reactors in 10 locations, with an installed capacity of 21 GW.