Knowing how much energy is used is the start to reducing electricity bills. The cost of electricity that appears on a bill goes up with the amount of energy used. This is not as straightforward as the power consumption of an appliance, since energy used depends on the time the appliance is consuming power.
Energy Consumption versus Power Consumption - It's about Time as well as Watts
Most people know that a kettle draws more power than, say, a refrigerator. The kettle draws around 3 kilowatts, a fridge is rated at about 150-300 watts. However, it would be a very unusual household that clocks up more energy usage through the kettle. That is because the kettle is only on for about five minutes, while the fridge is on 24 hours a day, 365 days a year.
The energy used is measured in kilowatt-hours, so a 3kW kettle on for five minutes consumes 3 x 5 / 60 = 0.25 kWh,whereas the fridge, assuming the motor runs half of the time drawing 0.15 kW, draws 0.15 x 24 / 2 = 1.8kWh. Boil the kettle seven times in a day, however, and its contribution to the electricity bill will be on a par with the fridge.
Measure the Energy Used with a Plug-In Energy Meter
Estimating the energy consumption of appliances like fridges is hard, since the power rated on the back will be the maximum power drawn. How often the motor runs and how long depends on many factors - the fridge efficiency, if it is frosted up, how hot the ambient temperature is. Measuring the actual energy consumed over a week will show if it is running inefficiently, if compared with a previous measurement. Often all that is needed is a defrost.
Using a plug-in energy meter to measure the energy used in a washing machine cycle can show the difference between using a hot wash and a cool wash. It will also show the horrific consumption of an electric clothes dryer!
Use Electronic Timeswitches to Reduce Standby Power
Home entertainment appliances like TVs, satellite receivers and personal video recorders can consume a surprising amount of power even when set standby. Some of these products need to be left on standby to update the electronic programme guide (EPG), however, they do not need to be left on standby all night. If they are switched off at the wall, a satellite receiver or PVR can take a few minutes to download the EPG. Using a timeswitch in the wall socket to feed the A/V system power strip, the equipment can be switched on only between 7am and 9:30 am and 17:00 to midnight weekdays, reducing standby consumption by half by switching the equipment off while the household is at work.
A plug-in energy meter is an excellent too to get real knowledge of how much power appliances take in the home. Knowledge is the key to reducing power consumption, lowering electricity bills and saving money and CO2 emissions.
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