The “Ask a Builder” series is dedicated to answering some of the many questions Fairbanks residents have about building, energy and the many other parts of home life.
Have you ever wondered how much an electrical appliance costs to use? For instance, how much does it cost to run your oven for four hours on Thanksgiving? Or, how much does it cost to dry a load of clothes?
There are many online calculators that will determine the cost of running an appliance if you are able to provide basic information such as how long it is run and the power or current that it draws. CCHRC has such a calculator for the Fairbanks area on our website here: www.cchrc.org/sites/all/files/calculator.html.
To use a calculator application, first look up the electricity it requires (which will be listed as watts or amps). This information is often found on the appliance itself, or in an appliance manual. Or, you can purchase a Kill A Watt meter at a hardware store, which allows you to measure the power consumption of appliances that plug into the wall.
You also can calculate the cost of using an electrical appliance yourself, but first you should be familiar with a few terms that describe the electricity that appliances use.
• Amp — The amount of current that an appliance draws is measured in amps. For instance, you might own a clothes dryer that draws between 10 and 15 amps. Smaller appliances require less current to run, for instance, many light bulbs draw less than one amp.
• Volt — A volt is the unit used to measure the electric potential in a circuit. You can think of volts as the force that makes current flow to an appliance. In the US, electric sockets that are found in residences are 120 volts or 240 volts for larger current draws — such as to run a dryer or an electric hot water heater.
• Watt — A watt is a measure of electrical power. Electrical power is calculated by multiplying voltage and current, so from the current rating, you can calculate the watts that an appliance will use. Information about the power the appliance uses is often given on the appliance too — think of a 100 watt light bulb.
• Kilowatt — A kilowatt is the name given to 1,000 watts, just like 1 mile is 5,280 feet.
• Kilowatt-hour (kWh) — A kWh is a measure of electric energy, which is what the electric company sells to you. To know the cost of running an appliance, you need to know the kilowatt-hours that it uses. To do this, you have to figure out the power draw (kilowatts) and multiply it by the amount of time that you will use the appliance (hours). Let’s consider some examples.
First, consider a television that is rated to use a current of 2 amps. To begin, convert the current draw to power by multiplying the current by the voltage from the socket: 2 amps x 120 Volts = 240 watts. To convert to kilowatts, divide by 1,000. The television uses 0.24 kW. Now let’s assume that your family watches TV each night for 3 hours. To find the electrical energy you will need to buy from your utility, multiply 0.24 kW x 3 hours = 0.72 kWh. In Fairbanks, electricity costs approximately $0.18 per kWh, so the TV will cost about $0.13 every time you watch it for 3 hours.
For the second example, let’s imagine that the appliance lists power draw instead of the current: an oven uses approximately 4,000 watts, or 4 kW. If you have the oven on for 2 hours while you bake dinner, you will have used 8 kWh, which will cost $1.44.
Lastly, it’s good to be aware of ghost loads, or electricity used by appliances that are not on all the time but are plugged in all the time — such as a television or a phone charger.
If you don’t know if an appliance has a ghost load, a Kill A Watt meter is a handy tool for figuring this out. Even though ghost loads are small, if your house has several appliances with ghost loads, they could add up in the course of a month.
The good news is that they are easy to prevent — simply unplug appliances that are not in use, or plug them into a power strip that can be turned off.
Ask a Builder articles promote awareness of home-related issues. If you have a question, contact us at cchrc.org or (907) 457-3454.