ToolNestFree Electricity Cost Calculator
Last updated: October 25, 2026
Quick answer: A space heater and an LED bulb can both be 'on' for hours, but one costs about 150 times more to run — and the difference is just watts times hours times your electricity rate. This free electricity cost calculator turns any appliance into dollars: enter its wattage, hours per day, and your price per kWh, and it shows the kWh and cost per day, week, month, and year, with presets for the appliances people ask about most — fridge, TV, gaming PC, space heater, air conditioner, dryer, water heater, and EV charger. Everything runs in your browser; nothing is uploaded.
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Formula: kWh per day = (watts ÷ 1,000) × hours per day × duty cycle × quantity. Cost = kWh × rate. Month = daily × 30, year = daily × 365. The default rate, 18.31 cents/kWh, is the US residential average (EIA, July 2026) — replace it with the rate on your own bill for an exact figure, since delivery charges, taxes, and tiered pricing sit outside the energy rate. Wattages are typical values; check the label on your appliance. Appliances that cycle (fridges, air conditioners) do not draw full power continuously — use the duty-cycle field or the preset's cycling value.
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How to Use the Electricity Cost Calculator
- Pick an appliance preset to fill in typical watts and hours, or enter your own numbers from the appliance label — watts are printed on the back, bottom, or power adapter of most devices.
- Enter your electricity rate in cents per kWh from your bill. If your bill only shows a total, divide the total amount due by the kWh used that month for an all-in rate.
- Set the duty cycle if the appliance cycles on and off: a fridge rated 150 W that runs about a third of the time is 33%, not 100% — the preset handles this for you.
- Click Calculate cost to see kWh and dollars per day, week, month, and year, plus the cost per hour of running it.
- Compare before you buy or replace: run the old appliance and the new one through the same rate and hours, and the yearly difference is the payback math for the upgrade.
Why Use Our Electricity Cost Calculator?
- Day, week, month, and year costs — one input gives all four horizons, so a $2-a-day habit and a $65-a-month bill are the same number, seen both ways.
- Common-appliance presets — fridge, TV, gaming PC, space heater, air conditioner, dryer, water heater, and EV charger with typical watts and hours pre-filled.
- Duty-cycle support — cycling appliances (fridges, AC units, heaters with thermostats) cost far less than their nameplate watts suggest; the duty field models that honestly.
- Your own rate, not a guess — the US average (18.31¢/kWh) is only the default; entering your bill's rate makes the result exact for your utility.
- Quantity multiplier — ten LED bulbs, two space heaters, or a bank of monitors: scale the result without retyping.
- 100% client-side — your rate and usage never leave your browser; no signup, no account.
Common Use Cases
- Deciding whether to replace an old appliance: Run the old fridge (say 250 W at 50% duty) against a new one (150 W at 33%) at your rate: the yearly difference is the real payback period for the purchase price, not the marketing claim.
- Explaining a high bill: Plug in the space heater, the dryer, and the water heater at your household's actual hours — one of them usually explains the spike, and knowing which one stops the argument about who left the lights on.
- Sizing a home battery or solar offset: Add up the daily kWh of the loads you want to cover (EV charging alone can be 28.8 kWh a day) before sizing a battery — the calculator's daily kWh figure is the input solar and battery quotes are built from.
- Landlord and renter cost splits: When a rental includes a heater, a dryer, or an EV charger on a shared meter, the per-appliance monthly cost gives a defensible split instead of a flat guess.
- Shifting laundry and dishwashing off-peak: A household on a time-of-use tariff moves its five weekly dryer loads and nightly dishwasher run to off-peak hours: the same 3 kWh dryer load costs $0.45 instead of $0.90, and the weekly saving of about $2.25 compounds to roughly $117 a year. The calculator quantifies it: run the dryer once at the peak rate and once off-peak, and the two monthly figures are the argument for a timer plug.
- Heat pump versus baseboard for a spare room: Heating a guest room with a 1,500 W baseboard heater for 8 hours a day through a 30-day month costs $65.92 at 18.31 cents/kWh. A mini-split heat pump delivering the same heat at COP 3 costs about $21.97 for the same month. The $44-a-month gap is the payback math for the mini-split, and it is computed from two runs of this calculator, not from a sales brochure.
- Pricing a holiday light display: Ten LED strings at 10 W each draw 100 W; six hours a night for 30 nights is 18 kWh, about $3.30 a month. The same display in old incandescent strings at roughly 1,000 W would be 180 kWh, about $32.96. The calculator settles the annual neighborhood debate about whether the lights are worth it — LEDs yes, incandescents maybe not.
Electricity Cost Calculator vs Alternatives
- EverydayTools' electricity cost calculator: A strong niche tool with time-of-use peak/off-peak rates and a detailed appliance table — the most complete free option for tariff nerds. Ours is the faster answer: watts, hours, rate, duty cycle, and all four horizons on one screen.
- WattItWillCost.me: A clean single-purpose calculator with a big typical-wattage table and volts × amps support. Ours adds the duty-cycle field for cycling appliances, quantity scaling, and copyable summaries.
- Your utility's bill breakdown: Authoritative for your total, and the only source for your exact tariff — but it won't tell you what one appliance costs. Use the bill for your rate, this calculator for the per-appliance split.
- A smart plug with energy monitoring: The ground truth for one device's actual draw, and the right way to settle a disputed wattage. It costs money per plug and measures one outlet at a time; use the calculator for every other appliance and the plug for the one you can't pin down.
- US DOE Energy Saver appliance estimator: The official reference: typical wattages and annual costs for common appliances, from the source utilities themselves quote. It is a table, not a calculator — no custom rate, hours, or duty cycle — so use it to check a wattage, then come back here for your household's actual numbers.
- Kill A Watt meter plus a spreadsheet: The measurement-first route: plug the meter in, read the real kWh over a week, and do the rate math yourself. Unbeatable for settling a disputed appliance, but it costs money per meter, measures one outlet at a time, and the spreadsheet is yours to maintain.
Bottom line: your utility bill tells you the total, a smart plug tells you one device exactly, and the tariff-focused tools tell you the most about rates. For the everyday question — 'what does this appliance cost me to run?' — watts, hours, rate, and duty cycle on one page is the whole job, and this page does it free.
Frequently Asked Questions
How do I calculate the electricity cost of an appliance?
Multiply watts by hours, divide by 1,000 to get kilowatt-hours (kWh), then multiply by your rate: cost = (watts × hours ÷ 1,000) × rate per kWh. A 1,500 W space heater running 8 hours uses 12 kWh; at 18.31¢/kWh that is $2.20 a day, $65.92 a month (× 30 days), and $801.98 a year (× 365 days). The calculator does this and scales it to all four horizons at once.
Where do I find how many watts my appliance uses?
On the label on the back or bottom of the unit, on the power adapter, or in the manual. If it only lists amps, multiply by your outlet voltage to get watts (120 V in the US, so 10 A ≈ 1,200 W). Note that the label usually shows maximum draw: for appliances with motors or compressors, typical draw is lower, and a smart plug with energy monitoring gives the real measured number.
What electricity rate should I use?
The best number is on your own bill: divide the total amount due by the kWh used that month for an all-in rate that includes delivery charges and taxes. If you don't have a bill handy, the US residential average of about 18.31 cents/kWh (EIA, July 2026) is a reasonable starting point — but rates vary widely by state and utility, from under 11¢ to over 30¢ per kWh.
Why is my real bill higher than the calculator says?
The calculator estimates the energy charge only. Utilities also add a fixed monthly service fee, delivery charges, taxes, and sometimes demand charges or tiered pricing that raises the rate past a usage threshold. Cycling appliances also run harder in extreme weather than their typical duty cycle suggests. Treat the result as the energy portion of the bill, not the whole bill.
How much does it cost to run a fridge, a TV, or a gaming PC?
At 18.31¢/kWh: a modern fridge (150 W, ~33% duty) runs about $6.53 a month; a 100 W LED TV at 5 hours a day about $2.75 a month; a 450 W gaming PC at 5 hours a day about $12.36 a month. The expensive items are the heaters: a 1,500 W space heater at 8 hours a day is $65.92 a month, and a Level 2 EV charger at 7,200 W for 4 hours a day is about $158.20 a month.
Does standby (phantom) power matter?
For one device, rarely: a TV or router on standby draws a few watts, worth pennies a month each. Across a whole entertainment center left on standby 24 hours a day it adds up to a few dollars a month — worth a power strip, but not worth worrying about compared with one space heater, which can cost more in a week than a year of standby draw.
What is the difference between kW and kWh?
kW (kilowatts) is a rate — how fast power flows right now. kWh (kilowatt-hours) is an amount — power multiplied by time — and it is what your bill charges for. A 1,500 W space heater draws 1.5 kW; run it for one hour and you have used 1.5 kWh. A 100 W bulb run for 10 hours also uses 1 kWh. Same energy, very different appliances — which is why the calculator asks for watts and hours separately, never just one of them.
Can I save money by running appliances off-peak?
On a time-of-use tariff, yes — off-peak rates are often roughly half the peak rate. A 3,000 W dryer load uses 3 kWh; at a 30-cent peak rate that is $0.90, at a 15-cent off-peak rate $0.45. Shifting five dryer loads a week off-peak saves about $2.25 a week, roughly $117 a year, for changing nothing but the hour you press start. The calculator uses a single rate, so run it twice — once at your peak rate, once off-peak — and the difference is your saving.
What is tiered electricity pricing?
Some utilities charge a lower rate for the first block of usage each month and a higher rate above it — for example, 16 cents/kWh for the first 500 kWh, then 28 cents/kWh after that. If you cross a tier, no single rate describes your bill: use the blended rate, total bill divided by total kWh. At 600 kWh on that example tariff, (500 × $0.16 + 100 × $0.28) ÷ 600 = $0.18/kWh blended. Enter that blended figure in the calculator for totals that match your bill.
Does a heat pump really cost less than a space heater?
Roughly a third as much for the same heat. A resistance heater turns 1,500 W of electricity into 1,500 W of heat; a heat pump with a COP of 3 moves about 1,500 W of heat while drawing only ~500 W. At 18.31 cents/kWh, eight hours of heating costs $2.20 a day with the resistance heater and about $0.73 with the heat pump — $65.92 versus about $21.97 over a 30-day month. That is the whole economic case for heat pumps in one division.
Why does my air conditioner cost so much more in a heatwave?
Because its duty cycle climbs with the temperature. A 1,500 W window unit at 60% duty for 8 hours uses 7.2 kWh a day ($1.32 at 18.31 cents/kWh); in a heatwave at 90% duty the same unit uses 10.8 kWh ($1.98) — 50% more for the same hours, because it barely switches off. Every degree you lower the thermostat adds roughly a few percent to runtime, which is why the calculator's duty-cycle field matters more in July than in April.
What uses the most electricity in a typical home?
Heating and cooling first, water heating second, then large appliances — lighting is a rounding error by comparison since LEDs arrived. An electric water heater at 4,500 W for 3 hours a day uses 13.5 kWh a day, about $2.47 a day or $74 a month at 18.31 cents/kWh. If your bill jumped and nothing changed, check the heaters first: one space heater running all month costs more than every LED bulb in the house combined.