Electric energy Electric energy means the energy and service provided by an electricity seller. The amount of energy to be billed is most commonly based on the volume of electricity (kWh) consumed during the billing period.  Electricity transmission Electricity transmission is provided by the local distribution system operator. In Helsinki, the operator is Helen Electricity Network Ltd. The function of the electricity network is to transfer electricity produced in power plants to consumers. The electricity network is maintained by the electricity transmission charges. The Energy Authority monitors the charges to ensure they are reasonable.  Electricity tax Electricity tax is paid on the consumption of electricity. The tax consists of excise duty on electricity and a security of supply charge. The distribution system operator bills the electricity tax from the customer along with the transmission charge and passes it on to the government. Kilowatt-hour (kWh) The watt-hour (Wh) is the unit of energy corresponding to the wattage output for one hour. Generally, the unit of measuring electric energy is the kilowatt-hour (kWh), which is 1,000 Watt-hours.