Transmitting electricity at high voltage reduces the fraction of energy lost to
Joule heating, which varies by conductor type, the current, and the transmission distance. For example, a 100 mi (160 km) span at 765 kV carrying 1000 MW of power can have losses of 0.5% to 1.1%. A 345 kV line carrying the same load across the same distance has losses of 4.2%.
[24] For a given amount of power, a higher voltage reduces the current and thus the
resistive losses. For example, raising the voltage by a factor of 10 reduces the current by a corresponding factor of 10 and therefore the I 2 R
losses by a factor of 100, provided the same sized conductors are used in both cases. Even if the conductor size (cross-sectional area) is decreased ten-fold to match the lower current, the I 2 R
losses are still reduced ten-fold using the higher voltage.