Volts, Amps, Btu? What do they mean, and how do they affect your energy use?
The energy consumption of your appliance can be difficult to calculate, as it is often expressed in different measurement units. For example, while your 2-slice toaster might use 2 watts and your kettle 1 watt, your vacuum cleaner might use 12 Amps, your air conditioner 8000 Btu, and your fridge might be given an EnerGuide rating of 718 kWh/year. Our guide explains what these different measurements mean so that you can use them to estimate your electricity consumption.
Volts and Amps
Volts and Amps are both measures of electricity. A Volt is the potential amount of work, and an Amp (Ampere) is the amount of charge passing through the electrical wire every second. In an electrical system, a Watt equals the voltage multiplied by the current.
In Canada, electrical current for residential sockets is 120 V. Therefore, your 12 Amp vacuum cleaner has a capacity of 1.440 kW. If you use it for half an hour, you will have used 0.72 kWh.
British Thermal Unit (Btu)
A Btu is the amount of heat that is needed to raise a pound of water by one degree Fahrenheit. The HVAC industry uses Btu to measure the quantity of heat that an air conditioning unit can remove from a room per hour. 1000 Btu are equal to 0.2931 kWh.
Energy Efficiency Ratio
However, the Btu capacity of your air conditioning unit alone is not enough to calculate its energy consumption. For this you need to know the a/c unit's energy efficiency ratio (EER). The EER is the ratio of the cooling capacity, in Btu per hour, to the power input (in watts).
Energy Efficiency Ratio (EER) = British Thermal Unit (Btu) : Watts (W)
The EER of your a/c unit should be marked; you should be able to find it on the unit's EnerGuide label. The higher the number, the more efficient the a/c unit. If you cannot find the EER, you can estimate a rating of 10 for a relatively new unit, and 7 or 8 for an old one.
EnerGuide ratings are part of a Government of Canada labelling program designed to encourage greater energy efficiency in consumer items (such as household appliances, light-duty vehicles, and houses). As part of Canada’s energy efficiency regulations, all household appliances must be tested for energy performance, to ensure that they meet energy efficiency standards and so that their average annual energy consumption can be estimated. The EnerGuide kWh rating therefore indicates how much electric energy your appliance is expected to use in a year under normal conditions.