That space heater is $1.80 a day. Every day. Quietly, in the corner, like a subscription.
Use this free electricity cost calculator to find what any appliance costs to run. Enter its wattage, hours used per day, and your price per kWh, and get the daily cost — then multiply out to see the monthly and yearly damage.
Electricity bills feel like one unexplained number because they arrive as a total. Broken down per device, they become obvious: a few high-wattage items running for hours dominate the bill, and the gadgets people worry about barely register.
What This Electricity Cost Calculator Does
- Calculates the daily running cost of any appliance
- Converts watts and hours into kWh, the unit your utility bills
- Lets you compare devices and find what is actually driving the bill
- Multiply by 30 or 365 for monthly and annual figures (see the notes)
How to Use the Electricity Cost Calculator
Inputs:
- Watts — the appliance's power draw, from the label, manual, or a plug-in meter
- Hours/Day — how long it actually runs, not how long it is plugged in
- Cost/kWh — your electricity rate (default $0.15; check your bill, US averages run $0.11–0.45 depending on the state)
Steps:
- Find the wattage on the appliance label or nameplate
- Estimate realistic daily run hours — a fridge compressor cycles about 8 hours a day, not 24
- Enter your rate per kWh from your bill and click Calculate
- Multiply the daily cost by 30 for a month and 365 for a year. The yearly number is the one that changes behavior
How the Calculation Works
kWh per day = (Watts × Hours) ÷ 1,000
Daily Cost = kWh × Price per kWh
Yearly Cost = Daily Cost × 365
- Divide by 1,000 because utilities bill kilowatt-hours: 1 kWh = 1,000 watts for one hour
- Typical wattages: LED bulb 10 W · laptop 50 W · TV 100 W · fridge 150 W (cycling) · desktop PC + monitor 300 W · window AC 1,000 W · space heater 1,500 W · electric dryer 3,000 W
- Appliances with heating elements or compressors dominate bills. Electronics are rounding errors by comparison
- Standby draw is real but small: 1–5 W per device, a few dollars a year each — it adds up across 30 devices, not one
Worked Example: 1,500 W space heater, 6 hours/day, $0.16/kWh
- kWh per day = (1,500 × 6) ÷ 1,000 = 9 kWh
- Daily cost = 9 × 0.16 = $1.44
- Monthly = $43.20 · over a 5-month winter = $216
- A 10 W LED bulb running the same 6 hours costs $0.0096 a day — $3.50 a year. The heater costs 150 times more than the bulb, which is worth knowing before you obsess over light switches.
Tips (From People Who Have Made These Mistakes)
- Find your real rate on your bill: total charges ÷ kWh used. The advertised supply rate excludes delivery fees, which are often half the bill
- Rank targets by watts × hours, not by how modern the device looks. Heating, cooling, water heating, and drying are almost always the top four
- A $25 plug-in energy meter settles arguments permanently and usually pays for itself in one discovery
- On a time-of-use plan, shifting the dryer and dishwasher to off-peak hours can cut those costs 30–50% with zero behavior change beyond a timer
Frequently Asked Questions
How do I calculate electricity cost?
Multiply watts by hours, divide by 1,000 for kWh, then multiply by your rate. A 100 W TV for 5 hours at $0.15/kWh: (100 × 5) ÷ 1,000 × 0.15 = $0.075 per day.
How much does it cost to run a space heater?
A 1,500 W heater uses 1.5 kWh per hour — about $0.23 per hour at $0.15/kWh, or $1.80 for an 8-hour night. Running one all winter routinely adds $150–300 to the bill.
What is a kWh?
A kilowatt-hour: 1,000 watts drawn for one hour. It is the unit utilities bill. A 1,000 W appliance for 1 hour, or a 100 W appliance for 10 hours, both use 1 kWh.
How much electricity does a refrigerator use?
A modern fridge draws 100–200 W but cycles roughly 8 hours a day, so about 1.2–1.6 kWh daily — $65–90 a year at $0.15/kWh. Older units can easily double that.
Does unplugging devices actually save money?
A little. Standby draw is typically 1–5 W per device, so unplugging one saves a few dollars a year. Worth a smart power strip for an entertainment center; not worth unplugging the microwave nightly.
Mini Roast Disclaimer
We roast the number, not you. The gaming PC is not the problem. The gaming PC left rendering overnight for three weeks is a different conversation.
Reality Check
Nameplate wattage is usually the maximum draw, not the average — motors, compressors, and thermostatically controlled devices cycle, so real consumption is often 30–60% lower. Tiered and time-of-use rates also mean your marginal cost may differ from your average. A plug-in meter measures what estimates approximate.