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Formula
Cost = (Watts × Hours per day ÷ 1,000) × Days used × Price per kWh
- Watts
- the appliance's power draw (or enter its kWh per day directly)
- Hours per day
- how long it runs on a day you use it
- Days used
- days of use in the period; days per week ÷ 7 × 365 for a year
- Price per kWh
- your electricity rate, in cents or dollars per kilowatt-hour
What it costs to run an appliance
Your electric bill is a single number, but it’s built from dozens of devices. The electricity cost calculator splits out one of them, a space heater, a gaming PC, a dehumidifier, and tells you what it adds to your bill each day, month and year at your own rate.
It has two modes. From watts takes the power rating and the hours of use. From kWh per day is for appliances you’ve measured with a plug-in meter, or ones that cycle on and off, like a fridge, where a daily energy figure is more honest than the label.
How to use the calculator
- Choose a mode and enter the wattage (W or kW) and hours used per day, or the kWh per day.
- Set days used per week. Seven is every day; five fits a weekday office or a workshop.
- Enter your electricity rate and choose cents or dollars per kWh. The calculator never fills in a price, because rates vary more than threefold between states.
The electricity cost calculator shows the monthly cost first, then the cost per day of use, per year and per hour, plus the energy behind each figure.
How to calculate electricity cost by hand
The formula has three steps: convert to kilowatts, multiply by time, then multiply by price.
Cost = Watts × Hours ÷ 1,000 × Rate per kWh
Say a 1,500 W space heater runs 5 hours a day, every day, at 18.31¢ per kWh:
- Energy per day: 1,500 × 5 ÷ 1,000 = 7.5 kWh
- Cost per day: 7.5 × $0.1831 = $1.37
- Cost per year: $1.37325 × 365 = $501.24
- Cost per month: $501.24 ÷ 12 = $41.77
When you don’t use it every day
Scale the year by the share of days you use it. A dishwasher using 1.2 kWh per load, run 4 days a week at 15¢, uses 1.2 × (4 ÷ 7 × 365) = 250.3 kWh a year. That costs $37.54 a year, or $3.13 a month.
Finding your real rate per kWh
The rate is the part people most often get wrong. Bills list a supply or energy charge, a separate delivery charge and a fixed customer charge. Add the per-kWh parts together for a marginal rate. For a simple all-in figure, divide the total bill by the kWh used. If $142.60 covered 780 kWh, your all-in rate is $142.60 ÷ 780 = 18.3¢.
Electricity prices by state
Where you live changes the answer more than almost anything else. The table uses EIA residential averages for July 2026 and prices one example load: a 1,000 W appliance running 4 hours a day (about 121.7 kWh a month).
| State | Residential rate (July 2026) | Monthly cost | Yearly cost |
|---|---|---|---|
| Hawaii | 48.00¢ | $58.40 | $700.80 |
| California | 33.61¢ | $40.89 | $490.71 |
| Massachusetts | 30.49¢ | $37.10 | $445.15 |
| New York | 29.90¢ | $36.38 | $436.54 |
| U.S. average | 18.31¢ | $22.28 | $267.33 |
| Texas | 15.88¢ | $19.32 | $231.85 |
| Arizona | 15.38¢ | $18.71 | $224.55 |
| Washington | 14.71¢ | $17.90 | $214.77 |
| Louisiana | 12.72¢ | $15.48 | $185.71 |
Summer prices run higher than the annual average in many states, so use the rate from your latest bill rather than a national figure.
Ways to use the results
Deciding whether an upgrade pays off
Price the old and new appliance side by side. If a new dehumidifier saves $6 a month and costs $240, it pays for itself in about 40 months. The same approach works for LED bulbs, heat pump water heaters and efficient monitors.
Budgeting for heating and cooling
Space heaters and window air conditioners are among the most expensive plug-in loads. Running them through the calculator before winter or summer shows what they’ll add to each bill.
Home office and hobby costs
If you work from home or run a 3D printer, crypto rig or kiln, enter its wattage and weekly schedule to see the yearly cost. That figure is also useful when you’re working out home-office expenses.
Checking a solar or battery plan
Knowing which loads cost the most helps you size a solar panel system around what you actually use.
Common mistakes
- Using the label maximum for a cycling appliance. A fridge rated 700 W may average under 2 kWh a day. Measure it, or use the EnergyGuide yearly kWh ÷ 365 in kWh-per-day mode.
- Entering cents as dollars. 16¢ is 0.16 dollars. The calculator flags a rate that looks like the wrong unit.
- Forgetting standby draw. TVs, game consoles and chargers can draw a few watts all day. Enter the standby watts with 24 hours to see what that costs.
- Using only the supply charge. Delivery is billed per kWh too and is often a large share of the price.
Glossary
- Rate (¢/kWh): what you pay for each kilowatt-hour; the number to multiply energy by.
- All-in rate: total bill ÷ total kWh, including fixed fees and delivery.
- Time-of-use plan: a tariff with cheaper off-peak and dearer peak hours.
- Standby power: the draw of a device that’s switched off but still plugged in.
If you only need the energy figure without a price, the kWh calculator works it out from watts or from amps and volts.
Worked examples
A window air conditioner
A 1,000 W air conditioner running 8 hours a day, every day, at 16¢ per kWh.
Inputs (From watts): Appliance power = 1000; Appliance power unit = Watts; Hours used per day = 8 h/day; Days used per week = 7 days; Electricity rate = 16; Rate unit = Cents per kWh (¢/kWh)
Energy per day = 1,000 W × 8 h ÷ 1,000 = 8 kWh Rate = 16¢ ÷ 100 = $0.16 per kWh Cost per day of use = 8 kWh × $0.16 = $1.28 (128¢) Days per year = 7 ÷ 7 × 365 = 365; yearly cost = 8 × 365 × $0.16 = $467.20 Monthly cost = $467.20 ÷ 12 = $38.93
Answer: Using 8 kWh a day, 7 days a week, at 16¢/kWh costs $1.28 per day of use, $38.93 a month and $467.20 a year.
A home office on weekdays
A computer and monitors drawing 250 W for 9 hours a day, 5 days a week, at $0.22 per kWh.
Inputs (From watts): Appliance power = 0.25; Appliance power unit = Kilowatts; Hours used per day = 9 h/day; Days used per week = 5 days; Electricity rate = 0.22; Rate unit = Dollars per kWh ($/kWh)
Energy per day = 250 W × 9 h ÷ 1,000 = 2.25 kWh Cost per day of use = 2.25 kWh × $0.22 = $0.50 (49.5¢) Days per year = 5 ÷ 7 × 365 = 260.71; yearly cost = 2.25 × 260.71 × $0.22 = $129.05 Monthly cost = $129.05 ÷ 12 = $10.75
Answer: Using 2.25 kWh a day, 5 days a week, at $0.22/kWh costs $0.50 per day of use, $10.75 a month and $129.05 a year.
A refrigerator from its kWh per day
A fridge using 1.5 kWh a day (about 548 kWh a year) at 13.5¢ per kWh.
Inputs (From kWh per day): Energy used per day of use = 1.5 kWh; Days used per week = 7 days; Electricity rate = 13.5; Rate unit = Cents per kWh (¢/kWh)
Rate = 13.5¢ ÷ 100 = $0.135 per kWh Cost per day of use = 1.5 kWh × $0.135 = $0.20 (20.25¢) Days per year = 7 ÷ 7 × 365 = 365; yearly cost = 1.5 × 365 × $0.135 = $73.91 Monthly cost = $73.91 ÷ 12 = $6.16
Answer: Using 1.5 kWh a day, 7 days a week, at 13.5¢/kWh costs $0.20 per day of use, $6.16 a month and $73.91 a year.
A phone charger (edge case)
A 5 W phone charger used 2 hours a day costs about 0.2¢ a day; the cost per day is shown in cents too.
Inputs (From watts): Appliance power = 5; Appliance power unit = Watts; Hours used per day = 2 h/day; Days used per week = 7 days; Electricity rate = 20; Rate unit = Cents per kWh (¢/kWh)
Energy per day = 5 W × 2 h ÷ 1,000 = 0.01 kWh Rate = 20¢ ÷ 100 = $0.2 per kWh Cost per day of use = 0.01 kWh × $0.2 = $0.00 (0.2¢) Days per year = 7 ÷ 7 × 365 = 365; yearly cost = 0.01 × 365 × $0.2 = $0.73 Monthly cost = $0.73 ÷ 12 = $0.06
Answer: Using 0.01 kWh a day, 7 days a week, at 20¢/kWh costs 0.2¢ per day of use, $0.06 a month and $0.73 a year.
Assumptions and limitations
- The rate is the one you enter. No price is assumed. The US average residential price (18.31¢ per kWh in July 2026, EIA) is shown only as a reference.
- A flat rate per kWh is used. Tiered, time-of-use and demand charges, and fixed monthly fees, are not modeled; dividing your total bill by the kWh used gives an all-in rate that includes them.
- The wattage is treated as the steady draw while the appliance is on. Appliances that cycle, such as refrigerators and air conditioners, use less than their label suggests; their kWh per day is more accurate.
- A year is 365 days and a month is a twelfth of a year (about 30.4 days). Days per week scales the year, so 5 days a week is 260.7 days of use.
- Money is rounded to the cent after the full calculation; very small daily costs are shown in cents.
Frequently asked questions
How do you calculate the electricity cost of an appliance?
Multiply the watts by the hours used and divide by 1,000 to get kWh, then multiply by your price per kWh. A 600 W microwave used 30 minutes a day uses 0.3 kWh, which costs about 5.5¢ a day at 18.31¢ per kWh.
How much does it cost to run 1,000 watts for an hour?
One kilowatt for one hour is exactly 1 kWh, so the cost equals your rate. At the July 2026 US average of 18.31¢, that's about 18¢; in Hawaii it was 48¢ and in Louisiana under 13¢.
What is the electricity cost formula?
Cost = watts × hours ÷ 1,000 × price per kWh. For a month, multiply the daily cost by 30.4; for a year, by 365, or by the number of days you actually use the appliance.
How do I find my price per kWh?
Look for the energy or supply charge on your bill. For an all-in figure, divide the total amount due by the kWh used. A $126.40 bill for 700 kWh works out to about 18.1¢ per kWh, including fees and delivery.
Why is my bill higher than the calculator suggests?
The label wattage is often a maximum, many devices draw standby power when off, and bills add fixed customer charges and taxes. Your bill also covers every appliance in the house, not just the one you entered.
Is it cheaper to run appliances at night?
Only on a time-of-use plan, where off-peak hours are priced lower. On a flat-rate plan a kWh costs the same at any hour. Check your plan, then enter the off-peak rate to see the saving.
How much electricity does a typical home use?
The EIA reports that the average US residential customer bought 10,791 kWh in 2022, about 899 kWh a month. At 18.31¢ that would be roughly $165 a month before fixed charges.
Sources
- Electric Power Monthly, Table 5.6.A: Average Price of Electricity to Ultimate Customers by End-Use Sector, by State — U.S. Energy Information Administration. Checked October 10, 2026.
- How much electricity does an American home use? — U.S. Energy Information Administration. Checked October 10, 2026.
- Electricity explained: Measuring electricity — U.S. Energy Information Administration. Checked October 10, 2026.