While not everyone can be a physics expert, understanding your energy use shouldn’t be a foreign concept. Knowledge about your energy use is a good first step in making changes to your energy consumption and lowering your electricity bill.

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How energy is measured

A kilowatt, also abbreviated kW, is a globally recognized standard for measuring electricity. One kilowatt is equal to 1,000 watts.

Your electricity company charges by how much electricity you use per kilowatt hour (kWh). To put it simply, this means it measures the number of kilowatts you use over time.

For example: A 100 watt light bulb uses 0.1 kilowatts each hour. It would take 10 hours for the light to consume 1 kWh of energy. If your energy company charges you a rate of $0.10 for each kWh, you would pay $0.10 to use a light every 10 hours. It may not seem like much now, but small amounts of energy use add up over the course of a month.

Calculating household usage

Most household appliances have wattage listed on the label, making calculating the energy cost easy. To find the kilowatts used by an appliance, you simply divide the watts listed on the appliance by 1,000 (the number of watts in a kilowatt) and then multiply by the hours used.

For example:You used a 400 watt radio for one hour today. Since we know a kilowatt is 1,000 watts, we divide the radio’s wattage by 1,000 (400/1,000=0.4). Now we know you used 0.4 kW of energy to listen to your radio today.

Next, we have to multiply the kW (0.4) by the hours of use (1) to calculate the kWh used (0.4 x 1 = 0.4).In this case, you only used 0.4 kWh to listen to your radio. However, if you had used the radio for two hours, you would have doubled your usage to 0.8 kWh (0.4 x 2 =0.8).

Fun facts

  • According to the U.S. Energy Information Administration, the average household electricity use is 11, 496 kWh per year, or 958 kWh per month.
  • Since the refrigerator has to run constantly, it is one of the biggest energy users in the home. A refrigerator can use anywhere from 80-200 kWh per month, depending on size and age of the unit. Smaller, newer units tend to use less energy to operate.
  • Energy-efficient appliances such as ENERGY STAR appliances use about 15% less energy than other models.
  • Baking in the oven uses 3.2 kW per hour. But cooking on the stovetop also uses significant energy. The large burner uses 2.4 kW per hour and the small burner uses 1.2 kW per hour.
  • An electric dryer uses 2.7 KWh per load. If you dry two loads of laundry every week, that is 208.8 kWh consumed each year!
  • An electric blanket uses 1 kWh for each night of use.
  • The average family of four uses 400 kWh to run the water heater each month, or 4,800 kWh per year.
  • Central air conditioning uses 1.2 kWh for each hour of use. Using the unit all day consumes 28.8 kWh.
  • A compact fluorescent light bulb (CFL) uses .025 kWh per hour. These bulbs provide energy savings since a typical 100-watt bulb uses .1 kWh for each hour of use. Changing to CFLs could lower your lighting costs by 75%.

Smart meters

Many households now benefit from smart meters. These meters, placed outside the home, measure electricity use and communicate with your utility provider on a daily basis. As an advantage to the consumer, the meter also displays up-to-date information on your energy usage. This allows you to better manage your energy use and calculate your energy bill before it arrives. If you are using more energy than normal, make changes to your energy usage to lower your electricity costs. Through this meter, you can easily take note of energy savings when you make changes to things such as lighting or air conditioning use.