How to Estimate Home Appliance Energy Usage
Estimating home appliance usage can be useful for a few reasons. It can help a household plan an annual budget for utilities, help decide whether it is necessary to upgrade some appliances to energy efficient models, and help plan ways to cut down on appliance usage to help save energy and money. By calculating the approximate cost of using home appliances, these decisions can be made about home energy usage. It is always beneficial for the environment to help cut down on energy consumption, so even making small changes, such as unplugging appliances when not in use, can collectively help everyone in a household consume less energy.
Formula for Estimating Energy Consumption
To estimate energy consumption of an appliance, two numbers are needed: the wattage of the appliance and the number of hours that the appliance is in use per day. The wattage of the appliance can usually be found on the appliance itself. If the wattage cannot be found, manufacturers’ websites may list the wattages of different models, or a common wattage for that appliance can be found on the Internet. The following is the formula, which will give the result of daily kilowatt-hour consumption (1 kilowatt (kW) = 1,000 Watts):
Wattage of Appliance × Hours Used Per Day ÷ 1000 = Daily Kilowatt-hour (kWh) consumption
Microwave: 1,000 watts
Hours used per day: 0.25 hours
1,000 watts × 0.25 hours= 250
250 ÷ 1,000 = 0.25 kWh
To calculate annual consumption, multiply the result from this formula by the number of days that the appliance is in use throughout the year.
Previous calculation of microwave consumption per day: 0.25 kWh
If the appliance is used every day, the cost would be:
0.25kWh × 365 days = 91.25 kWh
To calculate the annual cost, take the previous calculation of annual Kilowatt-hour consumption and multiply by the local utility rate of cost per kWh.
Hypothetical utility rate: $0.10/kWh
91.25 kWh × $0.10 = $9.13 per year
An exception to this rule is the refrigerator. When calculating the kWh of the refrigerator divide the hours of usage by three. Refrigerators cycle between being on and off even though it may be plugged in all the time; dividing by three gives a more accurate calculation of total usage time.
Most appliances have their wattage listed right on them. This wattage is the maximum amount of power drawn by the appliance; since most appliances have a range of settings, the amount of power used by the appliance will change depending on these settings. If the wattage is not listed on the appliance, the wattage can still be estimated by multiplying the current draw of the appliance in amperes by the voltage that is being used by the appliance. The result will be the wattage. This formula, amperes x voltage = wattage, can be used for any household appliance.
To determine the amperes of an appliance, one can look on the actual appliance to see if it written on a label or stamped on the appliance in place of a wattage. If the amperes are not found, a clamp-on ammeter, a tool used to measure current through one of the appliance’s wires, can be used to find this number. A reading using the clamp-on ammeter should be taken while the appliance is in use to determine an accurate current number. If the current of a motor is being measured, remember that the motor needs more current to start than when it is running constantly. After the first few seconds of turning the motor on, an accurate current reading can be taken. The voltage of most household appliances is 120 volts. Some larger appliances will have a voltage of 240 volts.
Some appliances that remain plugged in all the time will draw “vampire power” and use extra watt-hours. Appliances such as televisions, computers, phone chargers, and even toasters will have “phantom loads” of power drawn when not in use if they remain plugged in. To help reduce the energy consumption of these appliances when not in use, unplugging them will help cut these costs. To make this easier, a home owner can plug all items in a room that are not in use during the day into one power strip, and then shut off this power strip; only the power strip will need to be turned off instead of having to unplug each individual appliance.
Some Typical Wattages of Common Household Appliances
The following is a short list of some commonly used household appliances with a wattage or wattage range that is typical of that individual appliance. These wattages will vary by manufacturer and style of appliance. Also, the wattages are based on the highest setting for the appliance. For example when a blow dryer is set to high it is using its full wattage whereas on a low setting it will not be using as much power.
Air Conditioner: Room: 1000
Central: 2000 - 5000
Computer Laptop: 20 - 75
Desktop PC: 80 - 200
Coffee Maker: 1000
Clock Radio: 1
Clothes Dryer: Electric: 4000
Gas Heated: 300 - 400
Electric Range: 2,500
DVD player: 25
Dishwasher 1200 - 1500
Hair Dryer: 1000 - 1500
Heater (portable): 750–1500
Microwave: 600 - 1500
Vacuum Cleaner: Upright: 200 - 700
Washing Machine: 500
Additional Home Appliance Energy Usage Assistance
The following resources can help to calculate home appliance energy and help find ways to save energy in the home:
How Much Does it Cost Per Year to Operate Your Appliances? – A chart that approximates the cost of some common household appliances based on high and low hours of usage.
GE Data Visualization for Appliances – Pictures of appliances with wattages for estimating energy usage.
Energy Guidance: Appliance Shopping With the EnergyGuide Label – The Federal Trade Commission’s guide to understanding the EnergyGuide label while purchasing new appliances.
Appliance Energy Usage Calculator – An online calculator for determining annual kilowatts per hour used in a year along with annual cost based on a rate of ten cents per kilowatt hour. This cost will differ vary by region.
Typical Power Consumption – This chart shows the watts and annual kilowatt usage for a variety of appliances.
Small Appliances – Some small appliances can actually use more energy than big appliances. California Energy Commission put together this article on small appliances and how they often “leak” energy and what consumers can do to help prevent this from happening.
Appliance Energy Use Chart – A chart with the costs of using different appliances based on a rate of 9.5 cents per kWh.
Plug In and Save: Saving Energy with Electric Cars – Golden Valley Electric Association’s webpage on how to save energy for those who own electric cars; includes a video, information on plug in money saving devices, and a formula for approximating the cost of plugging in a car.
Assess Your Home – Energy Star’s guide to estimating your home energy use and cost based on your zip code, the square footage of your home, energy sources for your home, and your past year’s utility bills.
Importance of Residential Energy Use – Graphs on how much energy an average American household uses annually.
Consumer Guide to Home Energy Savings Online – The American Council for an Energy-Efficient Economy’s (ACEEE) guide for helping consumers save on energy usage in their households.
Unplug for Dollars: Stop “Vampire Power” Waste – An article on vampire power and what consumers can do to cut down on the costs from this excess energy consumption.
Energy Savers Tips: Home Office and Home Electronics – People who work from home are using more of their appliances on a daily basis and therefore consuming more energy. Energy Savers lists some tips to help cut down on these costs.
Power Consumption Table – A table showing the approximates wattages of household appliances along with a calculation form for determining costs located the bottom of the page.
Electricity Explained: Data and Statistics - U.S. Energy Information Administration's chart of electricity data including generation, capacity, consumption and price, and emissions information.
Additional Appliance Parts