Electricity cost is energy in kilowatt-hours (kWh) times your utility rate: first convert watts and run hours to kWh, then multiply by price per kWh to estimate what a device costs per day or month.
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Electricity cost = (Watts ÷ 1,000) × Hours used × Price per kWh. First convert watts to kilowatts, multiply by run hours to get kWh, then multiply by your utility rate.
Electricity cost estimates assume constant wattage and rate. Actual bills include tiered pricing, demand charges, taxes, and fees not captured here — check your utility statement for your exact rate.
Electricity is measured in kilowatt-hours (kWh) — the energy used by a 1,000-watt device running for one hour.
**The formula:**
1. Convert watts to kilowatts: kW = Watts ÷ 1,000
2. Calculate energy used: kWh = kW × Hours
3. Calculate cost: Cost = kWh × Rate ($/kWh)
**Example — Air conditioner:**
• Wattage: 1,500 W
• Run time: 8 hours/day
• Rate: $0.14/kWh
• kWh per day: (1,500 ÷ 1,000) × 8 = 12 kWh
• Cost per day: 12 × $0.14 = $1.68
• Cost per month (30 days): $50.40
**Average US electricity rates (2025):** ~$0.12–$0.22/kWh depending on state. Hawaii (~$0.38) and California (~$0.29) are highest; Louisiana (~$0.09) and Idaho (~$0.09) are lowest.
This calculator lets you stack multiple appliances to estimate your total monthly electricity bill.
Check the device label, manual, or product spec sheet. Common appliances: refrigerator 100–400W, washing machine 500W, air conditioner 1,000–3,500W, LED bulb 8–15W, desktop PC 60–300W.
Estimate how many hours the device runs daily. Use actual observed time, not just time plugged in — many devices cycle on and off.
Find your rate ($/kWh) on your electricity bill — usually listed as 'energy charge' or 'rate per kWh'. Select your country for a preset average if you do not have your bill handy.
Use the 'Add device' button to stack multiple appliances and see your estimated total daily, monthly, and annual cost.
Input
Gaming PC 400W + Monitor 27W + 5 hours/day + $0.15/kWhOutput
~$6.37/month(427 ÷ 1000) × 5 × 30 × $0.15 = 0.427 × 5 × 30 × 0.15 = $9.61 — but a gaming PC cycles between 150W (idle) and 400W (load), so real-world is lower.
Common real-world scenarios where this tool saves time.
Compare appliances side by side to find which devices consume the most electricity. Air conditioners, electric water heaters, and dryers are typically the top consumers.
A 500W appliance running 4 hours/day costs ~$8.76/month at $0.146/kWh; an efficient 300W equivalent saves $3.50/month — $42/year. Over 10 years: $420 in savings.
A 7.2kW home Level 2 charger running 8 hours per night uses 57.6 kWh — at $0.14/kWh that is $8.06/night or ~$242/month if charging daily.
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Identify which appliances to target for energy savings.
At $0.14/kWh — US average 2024.
| Appliance | Typical wattage | Cost per hour | Cost per month (4h/day) |
|---|---|---|---|
| LED bulb | 10W | $0.001 | $0.17 |
| Desktop PC | 150W | $0.02 | $2.52 |
| OLED TV (55-inch) | 100W | $0.01 | $1.68 |
| Window AC unit | 1,000W | $0.14 | $16.80 |
| Electric oven | 2,400W | $0.34 | $40.32 |
| Central AC | 3,500W | $0.49 | $58.80 |
| Electric water heater | 4,500W | $0.63 | N/A (thermostat-controlled) |
Actual wattage varies by model and age. Check the device label for rated watts.
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Check the label on the back or bottom of the device — it shows voltage (V) and either watts (W) or amps (A). If it shows amps, multiply by voltage to get watts: W = V × A. Alternatively, check the product manual or manufacturer website. A smart plug (Kill-A-Watt style meter) measures real-time actual consumption, which is more accurate than rated wattage.
A kilowatt-hour (kWh) is the unit of electricity on your bill. 1 kWh = 1,000 watts running for 1 hour. Ten 100W light bulbs running for 1 hour use 1 kWh. Your bill shows total kWh consumed in the billing period, multiplied by your rate ($/kWh) to give the energy charge.
Check your latest electricity bill — look for 'energy charge', 'rate per kWh', or 'distribution charge'. Your rate is typically between $0.10 and $0.40/kWh depending on location. In the US, the average residential rate is ~$0.146/kWh (2024 EIA data). Hawaii (~$0.38) and California (~$0.29) are highest.
A typical central AC unit (3,500W) running 8 hours/day at $0.14/kWh costs: (3,500 ÷ 1,000) × 8 × $0.14 = $3.92/day or ~$118/month. A window AC unit (1,000W) costs: 1 × 8 × $0.14 = $1.12/day or ~$33.60/month.
Ranked by typical monthly consumption: 1) Central AC/heat pump (400–1,200 kWh/mo), 2) Electric water heater (300–500 kWh/mo), 3) Electric dryer (75–150 kWh/mo), 4) Refrigerator (30–80 kWh/mo), 5) Washing machine (15–30 kWh/mo), 6) Dishwasher (15–25 kWh/mo). Lighting accounts for ~15% of a typical home bill.
Yes — 'standby power' or 'phantom load' from devices in standby consumes 5–10% of a typical home's electricity. Common standby consumers: TV (1–5W), microwave clock (2–3W), cable box (15–30W even when off), phone charger without phone plugged in (0.5–2W). Smart power strips cut standby power when devices are not in use.
An iPhone draws ~5W while charging and takes ~2 hours. Energy: (5 ÷ 1,000) × 2 = 0.01 kWh. At $0.14/kWh: $0.0014 per charge — about $0.51 per year if charged daily. Smartphone charging is negligible in a household electricity bill.
Not automatically — it uses a single constant rate. Many utilities charge tiered rates where consumption above a threshold is billed at a higher rate. For tiered billing, calculate costs for each tier separately, or use your bill's average rate (total bill ÷ total kWh) as an approximation.
Appliance wattage, usage hours, and rate inputs stay in your browser—they are not uploaded to EverydayTools servers.
Actual bills include tiered rates, demand charges, taxes, and fees not modeled here. Check your utility bill for exact rate. Financial results are estimates for planning only — not tax, legal, or investment advice. Verify with your employer, institution, or a qualified professional.
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Reviewed on 2026-06-08.