Each year, power plants world-wide send out 50 EJ, or about 14 trillion kWh, to consumers. Thus, approximately one eighth of primary energy (400 EJ) comes from the electrical outlet. The average US citizen consumes 270 kWh per day, with about 40 kWh per person per day from electrical power. However, this is mostly via industry and service providers, not direct home use.
Between the power plant and the outlet in your home are transmission lines and transformers; for example, a voltage of 10 kV at the producer is transformed to 400 kV for the transmission, which becomes finally 110 V for consumers in the United States or 230 V in Europe. High voltage networks reduce heat loss in the transmission as seen from Ohm’s law.
Ohm’s law is shown below with U the voltage measured in volts [V], R the resistance measured in ohms [Ω], and I the current measured in amperes [A]:
The electrical power, designated by P, is measured in watts [W]. It is the product of voltage and current:
The formula for power loss is found using Ohm’s law:
The electric power should be large compared to the power loss due to the electrical resistance of the power line. From the above equations, one can see that the transfer of electrical power should be done with the highest possible voltages.