The cost to run an electric heater depends on the type of house, size of room, and quality of insulation in the home. However,  the maximum consumption of the heater will be 1 kWh per kilowatt of heat. For example, if you have a 1500W heater the maximum it will use is 1.5 KWh. However,  the unit will cycle on and off so while the unit is off it will not consume any electricity. Electric heaters heat only the room you are in and not the entire house. They provide extra heat only where required and help to optimize energy consumption. Electricity costs vary across suppliers. If you check your bill you will be able to find out how much you are paying per KWh. In 2017,  the average cost in North America was $0.12 per KWh. For example: If the unit runs continuously for 10 hours without cycling off it will consume 1.5kWh x 10 hours x  $0.12 = $1.80.