Fig 10Why power lines run at high voltagesame power, different voltage46% lost
A power station sends 100 MW through a line with 5 Ω of resistance. Power is voltage times current, so the same power at a higher voltage needs less current. The heat lost in the line goes as the current squared, so raising the voltage tenfold cuts the loss a hundredfold. At 33 kV almost half the power would be lost as heat. At 400 kV, a typical long-distance voltage, the loss is 0.3%.