Electricity Cost Calculator: How Much Does It Cost to Run?

Every device’s running cost comes down to two numbers: how many kilowatt-hours it uses and what you pay for each one. The first depends on its power draw and how long it runs. The second depends a lot on where you live, from about 12 cents per kWh in the cheapest states to more than 40 in Hawaii. This calculator does the arithmetic and uses your state’s average residential price from the EIA unless you enter your own.

How it works

kW          = watts × quantity ÷ 1,000
kWh / year  = kW × hours per day × days per week × 52.14
cost        = kWh × price per kWh
per month   = yearly ÷ 12      per hour = kW × price

Watts are the device’s power draw while it runs. The label usually gives the maximum. Devices that cycle, like refrigerators, heaters on a thermostat, AC units and dehumidifiers, spend part of each hour off, so their average draw is lower. For those, a plug-in meter reading over a full day gives the best number.

Days per week lets you price something you only use on weekends or a few days a week. The calculator converts it to a yearly total with 52.14 weeks.

Price. By default the calculator uses the EIA’s year-to-date average residential price for your state. That figure is total revenue divided by kWh sold, so it includes delivery charges spread over usage. Your own bill’s total divided by its kWh is closer still.

What it doesn’t include: standby power when the device is “off”, demand charges and seasonal rate changes.

Worked example

A homeowner in Pennsylvania runs a 1,500-watt space heater in a home office for 8 hours a day, every day, through the winter. Pennsylvania’s EIA average is 21.13¢ per kWh.

• Power: 1,500 W ÷ 1,000 = 1.5 kW
• Daily use: 1.5 × 8 = 12 kWh, or 365 kWh a month
• Per hour: 1.5 × $0.2113 = about 32¢
• Per month: 365 × $0.2113 = about $77

By comparison, a 100-watt device left on around the clock in the same state costs about $15 a month. Small loads that never turn off add up.

Electricity prices by state: reference table

Average residential prices and what three common loads cost to run in each state, from most to least expensive.

Tips and common mistakes

Use your real rate. The state average is a good starting point, but rates vary a lot between utilities in the same state. Your bill’s total ÷ kWh is the number to use.

Measure, don’t guess, for cycling loads. A plug-in meter on a refrigerator for a week tells you more than its label. Many fridges draw 100 to 200 watts while running but use far less on average.

Watch heating elements. Anything that makes heat with electricity, like a space heater, kettle, dryer or water heater, draws a lot of power. A few hours a day can be a big share of a bill.

Look at standby. Game consoles, cable boxes and older electronics can draw several watts all the time. Smart power strips cut that.

Price a replacement before you buy. Run the old and the new appliance through the calculator with the same hours. The yearly difference, multiplied by the years you expect to keep it, is what the more efficient model is worth to you.

Compare with the EnergyGuide label. Major appliances carry a yellow label with yearly kWh measured under a standard test. Multiply it by your rate for a quick annual cost.