Electricity Cost Calculator

What the calculator works out

Electricity is sold by the kilowatt hour, and a kilowatt hour is 1,000 watts used for one hour. A device that draws 1,000 watts for 60 minutes uses 1 kWh. A device that draws 100 watts for 10 hours also uses 1 kWh. That single idea is the whole calculator: watts times hours, divided by 1,000, times the price on your bill.

The formula the page runs is kWh = watts x hours / 1,000, and cost = kWh x price per kWh. Enter the watts from the label on the appliance, the hours it runs on a normal day, how many days a month you use it, and the all in price you pay per kWh. The output covers one day, one month and twelve months, plus the cost of each hour of use.

Two numbers on the label are worth telling apart. The nameplate figure is the highest draw the device can pull, and the running figure is what it draws once it is going. A refrigerator nameplate may say 725 watts while the compressor averages 150 watts because it cycles on and off. Use the running figure when you have it, and read the section on refrigerators and other cycling loads before you trust a nameplate number.

The rate box wants the price you pay in full, not the teaser rate on a supplier mailer. On a United States residential bill that number is supply plus delivery, and the EIA puts the 2025 national average at 17.30 cents per kWh.

Worked example: a 1,500 watt space heater

A space heater is the cleanest example because it runs at a steady draw. Take 1,500 watts, 8 hours a day, 30 days a month, and 17.30 cents per kWh.

• Daily energy: 1,500 x 8 / 1,000 = 12 kWh
• Monthly energy: 12 x 30 = 360 kWh
• Cost a month: 360 x 0.173 = $62.28
• Cost a day: 12 x 0.173 = $2.08
• Cost an hour: 1.5 x 0.173 = $0.26
• Twelve months: 360 x 12 = 4,320 kWh, which is $747.36

The twelve month figure uses twelve 30 day months, which is 360 days. A strict 365 day year adds five more days of running: 4,380 kWh and $757.74. The gap is about ten dollars, and it exists because bills arrive monthly while the calendar does not.

Now cut one hour. Dropping from 8 hours to 7 saves 45 kWh a month, which is $7.78 on the bill and $93.42 over a year. That is the number to remember when a heater is the only thing keeping one room warm: the hours dial on the unit moves the bill more than the low and high heat setting does, because the low setting still runs the fan and the element, just less often.

A 1,500 watt heater on high for 8 hours is also a lot of heat for one room. Most of that energy ends up as heat in the room it sits in, so the honest comparison is not heater against nothing, it is heater against the house furnace or heat pump running less.

Worked example: the loads that run all day

Always on devices are cheap per hour and expensive per month, which is why they get missed. A cable box drawing 20 watts on standby around the clock is 14.4 kWh a month, or $2.49. Over a year that is 172.8 kWh and $29.89. One box is small. Four of them, plus a router and a game console in rest mode, is closer to 50 watts of constant load, which is 36 kWh a month and $6.23, or $74.74 a year for doing nothing.

A refrigerator is the other all day load, and the arithmetic has a trap. A modern ENERGY STAR full size unit averages roughly 150 watts while the compressor runs, but the compressor does not run 24 hours. The Department of Energy suggests dividing plugged in time by three to estimate real compressor hours, so 24 hours plugged in becomes 8 hours of running. That gives 1.2 kWh a day, 36 kWh a month and $6.23 on the bill, or 432 kWh and $74.74 over twelve months.

Use the nameplate number instead and the same fridge looks like a disaster: 725 watts for 24 hours is 17.4 kWh a day, 522 kWh a month, $90.31. The nameplate figure is a worst case that the unit never sustains. If you want the real number, a plug in energy meter costs about twenty dollars and reads the actual kWh over a week, which beats every table on the internet.

Compare that with a lamp. A 9 watt LED bulb for 5 hours a day is 1.35 kWh a month, or $0.23. Swapping bulbs is worth doing, but the savings are measured in dollars a year, not tens of dollars a month.

Appliance watts and what a month costs

The wattages below are typical running figures from the Ohio Consumers' Counsel appliance fact sheet, which collects the ranges utilities publish. Hours are assumptions that match how most households use the device, so treat the last two columns as a starting point and put your own hours in the calculator.

The nine rows add up to $291.37 a month at 17.30 cents per kWh, and the top three rows carry 83 percent of that total. That concentration is the useful part of the table. Chasing the last dollar out of a laptop charger is wasted effort when the air conditioner, the water heater and the heater are more than four fifths of the bill.

Heating and cooling numbers vary with the house, not just the appliance. A 3,500 watt central air conditioner in a leaky 1970s house runs far more hours than the same unit in a house with new windows, and the thermostat setting decides most of the difference. The 6 hours a day in the table is a mild climate average, not a promise.

What a kilowatt hour costs where you live

The national average hides a spread of more than two to one. The figures below are residential prices for July 2026 from the EIA Electric Power Monthly, Table 5.6.A, and they are the number to use in the rate box if your own bill is not in front of you.

Run the 1,500 watt heater for 8 hours a day in Massachusetts and the month is 360 kWh at 30.49 cents, which is $109.76. The same heater and the same hours in North Dakota is $48.28. The difference of $61.49 a month, or about $740.00 over twelve months, comes from the rate alone. Nothing about the heater changed.

Rates also move inside a state. In July 2026 the EIA reported 30.49 cents for Massachusetts and 21.72 cents for Pennsylvania, and both states buy power in the same regional market. Delivery charges, state efficiency programs and the mix of generation contracts explain most of that. Your own bill, not a state average, is the number that matters, and it is printed as a price per kWh or as a total divided by kWh used.

The average also drifts year to year. The EIA annual series reported 16.48 cents for all of 2024, 17.30 cents for 2025, and 17.55 cents for January and February of 2026. Using a rate from a five year old article will undersell a bill by a wide margin.

Hours matter more than wattage

Two devices can use the same energy with widely different wattages, and the hours decide which one costs more. A 5,000 watt dryer for one hour is 5 kWh. A 60 watt laptop for six hours is 0.36 kWh. The dryer draws 83 times the power and uses 14 times the energy, because it runs for a sixth as long.

Read that table as a menu. Going from 8 hours to 6 saves $15.57 a month. Going from 8 hours to 4 saves $31.14 a month, which is more than the dryer, dishwasher, fridge, television, laptop and cable box in the table above combined, $50.03.

This is why the usual advice, which is to swap bulbs and unplug chargers, feels ineffective to anyone who has tried it. Those changes are real but small. The big three loads are heating, cooling and hot water, and within those the lever is hours and thermostat setting rather than the price of the appliance. A heat pump water heater, a smart thermostat and a lid on the pot of pasta all do more than a drawer full of LED bulbs.

Why the estimate and your bill disagree

An estimate that lands within 10 percent of the bill is a good estimate. This page prices one device at the hours you give it, which is a different question from which fuel or heat pump is cheapest per unit of heat; that comparison needs cost per million Btu, not cost per kWh. Here is what else moves the two apart.

Cycling and duty cycle. Anything with a thermostat, which covers fridges, freezers, ovens, irons, water heaters and air conditioners, runs part of the time and idles the rest. Watts times hours assumes it runs the whole time, which overstates the energy for a cycling load and understates it for a device that starts more often than you think.

Nameplate against real draw. Labels show maximum. A 1,200 watt microwave pulls 1,200 watts only while the magnetron is on, and the display and fan draw a fraction of that for the rest of the minute.

Rate structure. Many United States utilities bill in tiers, so the price per kWh rises after a baseline amount, and a summer bill can be billed at a higher rate than a winter bill for the same kWh. Time of use plans price 5 pm to 9 pm higher than the middle of the night. A single rate in the calculator is an average of all that.

Fixed charges and taxes. A monthly customer charge of 10 to 20 dollars appears on the bill whether you use one kWh or 900. Sales tax and local fees sit on top in some states. Those lines do not scale with use, so an appliance estimate should be compared with the variable part of the bill.

Estimated reads. A bill marked estimate is a guess by the utility, corrected the next month. If the kWh on the bill jump by 40 percent with no change at home, the read is the first thing to check before blaming an appliance.

Cutting the number without buying anything

Start with the meter and the biggest load, not with a shopping list. Read the meter at the same time two days in a row with nothing unusual running, and the difference is the base load of the house. A base load of 20 kWh a day is 600 kWh a month, $103.80, before anyone turns on a light.

Then attack in order of size. Heating and cooling first: two degrees of thermostat change in the right direction is roughly 3 percent of the heating bill per degree in the Department of Energy energy saver guidance, and a smart schedule that drops the setpoint while the house is empty does more than any single appliance swap. Hot water second: a 120 degree tank setting instead of 140 costs little in shower time and trims standby loss, and a 10 minute shower instead of 20 halves the hot water draw.

Laundry third. Washing in cold water and hanging half the loads takes a 5,000 watt dryer out of the picture for those loads: 16 loads a month at 5 kWh each is 80 kWh, $13.84, and halving it saves $6.92 a month. Standby fourth: a power strip on the television, console and cable box, switched off at night, removes about 30 watts of constant load, which is 21.6 kWh a month and $3.74.

Rates last, because switching suppliers only helps after the usage is under control, and a lower rate on a high usage bill is still a high bill. If your state allows retail choice, compare the all in price per kWh including delivery, not the supply rate alone, and read the term length before signing.