Electricity Cost - Single Usage Calculator
Find out what a single run of any appliance actually costs in electricity. Enter the device wattage (or pick from 30 common appliances), how long it runs, and your local electricity rate. You instantly get the energy consumed in kWh, the cost per use, and the estimated CO2 emission for that one run. The "show your work" panel walks through every step of the math.
How to calculate the cost of a single appliance use
The formula has two steps. First, convert the device wattage from watts to kilowatts (divide by 1,000) and multiply by the run time in hours to get the energy consumed in kilowatt-hours (kWh). Second, multiply that kWh figure by your electricity rate, found on your monthly bill, to get the dollar cost. Written out: Cost = (Watts / 1,000) x Hours x Rate ($/kWh). For example, boiling water with a 1,500 W kettle for 3 minutes uses (1,500 / 1,000) x (3 / 60) = 1.5 x 0.05 = 0.075 kWh. At a rate of $0.16/kWh that costs about 1.2 cents per boil.
How to find your electricity rate
Your rate appears on your monthly electricity bill, usually labelled "energy charge" or "cost per kWh." In the United States, the national average was about $0.16/kWh in 2024, but state averages range from under $0.11/kWh in Louisiana to over $0.33/kWh in Hawaii. Rates also vary by season and by time of day if your utility offers time-of-use (TOU) pricing. Using your actual rate rather than the national average gives much more accurate results. If you cannot find it on your bill, log in to your utility account online, where most providers display it prominently.
Why the wattage on the label may differ from real consumption
The wattage printed on a device is usually the peak or rated draw, which the appliance reaches only under full load. Many devices use less in practice. A laptop rated at 65 W might average 25-35 W during typical browsing; a refrigerator cycles on and off and averages only about 150 W even though the compressor peaks higher. For the most accurate result, measure the actual draw with a smart plug that monitors energy consumption, such as a Kill A Watt meter. The figure it reports is the true average watt-hours consumed over a real usage session.
CO2 emissions and the electricity grid
Generating electricity produces greenhouse gas emissions, but the intensity varies enormously by region and energy source. This calculator uses the U.S. EPA eGRID average emission factor of approximately 386 g CO2-equivalent per kWh (2023 data). If your utility supplies a high share of renewables, your actual footprint is lower. If you are on a coal-heavy grid, it is higher. Reducing the number of high-draw appliance uses per day, or shifting usage to times when the grid runs cleaner (usually during daylight hours in solar-heavy regions), can meaningfully reduce your carbon footprint alongside your bill.
Typical wattage and cost per hour (at $0.16/kWh)
| Appliance | Typical wattage (W) | Cost per hour (USD) |
|---|---|---|
| LED bulb | 10 | $0.002 |
| Phone charger | 5 | $0.001 |
| Wi-Fi router | 12 | $0.002 |
| Laptop computer | 45 | $0.007 |
| Desktop PC + monitor | 230 | $0.037 |
| 32-inch LED TV | 50 | $0.008 |
| 55-inch LED TV | 120 | $0.019 |
| Ceiling fan | 75 | $0.012 |
| Coffee maker | 1,100 | $0.176 |
| Microwave | 1,200 | $0.192 |
| Electric kettle | 1,500 | $0.240 |
| Toaster | 850 | $0.136 |
| Hair dryer | 1,800 | $0.288 |
| Clothes iron | 1,000 | $0.160 |
| Vacuum cleaner | 700 | $0.112 |
| Dishwasher | 1,400 | $0.224 |
| Washing machine | 500 | $0.080 |
| Clothes dryer | 5,000 | $0.800 |
| Refrigerator | 150 | $0.024 |
| Electric oven | 2,200 | $0.352 |
| Window A/C unit | 1,400 | $0.224 |
| Central air conditioner | 3,500 | $0.560 |
| Space heater | 1,500 | $0.240 |
| Electric water heater | 4,500 | $0.720 |
| EV charger (Level 2) | 7,200 | $1.152 |
Approximate values. Actual wattage varies by brand, model, and usage intensity. Check the device nameplate for the exact figure.
Frequently asked questions
What is a kilowatt-hour (kWh) and how is it different from a watt?
A watt (W) is a unit of power, how fast energy is being used at any instant. A kilowatt-hour (kWh) is a unit of energy, the total amount consumed over time. Running a 1,000-watt (1 kW) device for exactly one hour uses 1 kWh. Your electricity bill charges you per kWh, not per watt, which is why converting is the key step in calculating cost.
How do I find the wattage of my appliance?
Check the label or nameplate on the back, bottom, or inside the door of the device. It usually lists watts (W) or amps (A) and volts (V). If you only see amps and volts, multiply them together to get watts: Watts = Amps x Volts. In the U.S., standard voltage is 120 V for most outlets and 240 V for large appliances like dryers and ovens. You can also check the manufacturer manual or product listing online.
Why does my electricity bill cost more than my calculation predicts?
Your bill includes more than just the energy charge. It typically adds transmission and distribution charges, customer service fees, taxes, and sometimes renewable energy surcharges. The energy-only rate used in this calculator covers the commodity cost of electricity but not those fixed and variable line items. To match your bill total exactly, divide your total bill amount by the total kWh used to get your all-in effective rate, then use that in the calculator.
Does leaving appliances plugged in when not in use cost money?
Yes. Many devices draw power even when switched off or in standby mode, a phenomenon called "standby power" or "phantom load." Common examples include TV boxes, game consoles, microwaves with a clock display, and phone chargers. A device drawing just 5 W in standby costs about $7 per year. Unplugging devices or using a smart power strip eliminates this cost.
How can I reduce the electricity cost of running an appliance?
The main levers are: (1) use a more efficient model - ENERGY STAR devices are 10-50% more efficient than standard equivalents; (2) reduce run time by using the appliance at its most efficient setting (full loads in dishwashers and washing machines, shorter boil times with the right kettle size); (3) shift use to off-peak hours if your utility offers time-of-use pricing, where rates can be 30-50% lower at night or on weekends; and (4) eliminate standby draw by unplugging or using smart plugs.
What appliances cost the most to run?
The biggest electricity users in a typical home are central air conditioning and heating (often 3,000-5,000 W), electric water heaters (4,500 W), clothes dryers (5,000 W), and EV chargers (7,200 W for Level 2). These high-wattage devices run for long periods, so their cost per use can be many times higher than small kitchen appliances even if individual sessions feel brief.
How accurate is the CO2 estimate?
The estimate uses the U.S. EPA eGRID national average emission factor of 386 g CO2-equivalent per kWh, which is a reasonable approximation for the average U.S. household. Your actual footprint depends on which power plants supply your local grid. States with a high share of hydropower, nuclear, or wind (like Washington, Vermont, or Iowa) have much lower emission intensities. States relying heavily on coal or gas have higher intensities. Check the EPA eGRID data for your specific grid subregion for the most accurate figure.