Electricity Cost Calculator (Watts, kWh & Monthly Bill)
Enter watts, hours, and your kWh rate to estimate what an appliance costs per day, month, and year—or price a monthly electric bill from kWh.
Electricity cost calculator
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How to Calculate Electricity Cost
Electricity is billed in kilowatt-hours. Divide watts by 1,000 to get kilowatts, multiply by hours to get kWh, then multiply by the price of one kWh. A 1,000 W load running 5 hours uses 5 kWh that day. At $0.18/kWh that is $0.90 for the day and $27 over 30 days.
How to Use This Electricity Cost Calculator
- Choose Appliance cost or Electricity bill.
- Enter watts or kW, hours per day, and quantity—or monthly kWh in bill mode.
- Enter your rate in cents/kWh or dollars/kWh. The US average is a starting point, not your tariff.
- Add more appliances if needed. Duty cycle is for devices that cycle, such as refrigerators.
Electricity Cost Formula
kWh/day = (watts ÷ 1,000) × hours/day × quantity × (duty % ÷ 100) × (days/week ÷ 7)
kWh/month = kWh/day × days/month
Cost = kWh × (cents per kWh ÷ 100)
Example: 1,500 W × 8 hours × 30 days = 360 kWh. At $0.1831/kWh the energy cost is $65.92. Time-of-use pricing applies the peak rate only to the peak hours you enter; remaining runtime uses the off-peak rate. Peak hours cannot exceed daily runtime.
How Much Does It Cost to Run Common Appliances?
Assumptions: 30 days and $0.1831/kWh (EIA July 2026 US residential average of 18.31 cents/kWh). Wattages are typical estimates.
| Appliance | Estimate | Hours/day | Cost/month |
|---|---|---|---|
| LED bulb | 10 W | 5 | $0.27 |
| Refrigerator | 150 W at 33% duty | 24 | $6.52 |
| Window / room AC | 1,500 W at 60% duty | 8 | $39.55 |
| Space heater | 1,500 W | 8 | $65.92 |
| TV | 100 W | 5 | $2.75 |
| Gaming PC | 427 W | 5 | $11.73 at 18.31¢; $9.61 at 15¢ |
| Washer + dryer | 500 W + 3,000 W | 1 each | $19.23 |
| EV charger | 7.2 kW | 4 | $158.20 |
Gaming PC check: 427 W × 5 h × 30 days × $0.15/kWh = $9.61/month, not $6.37. Idle draw is lower than 427 W; use a meter if you need measured watts.
How to Estimate Your Monthly Electricity Bill
Bill mode is for a kWh total you already have. Energy charges = kWh × rate. Add a customer charge or other fixed fee only if it is not already inside an all-in rate (total amount due ÷ kWh). Optional tax is applied to energy plus fixed charges. 600 kWh at $0.18/kWh plus a $12 fixed charge is $120 before tax.
Average Electricity Rates in the USA
Residential prices in this calculator come from EIA Electric Power Monthly Table 5.6.A for July 2026, released September 24, 2026. The US average is 18.31 cents/kWh. Those figures are monthly state averages of revenue per kWh, not a live quote from your utility, and a state can contain many tariffs.
Source: EIA Table 5.6.A. Always replace the preset with the rate on your bill.
How to Reduce Your Electricity Costs
- Cut hours first on the highest-cost row.
- Compare a lower-watt replacement in the efficiency section; payback uses the purchase price you type.
- Standby loads are small watts for many hours—add them as their own row if you care.
- If you have time-of-use rates, shift runtime into off-peak hours rather than guessing an average.
Common Electricity Cost Calculation Mistakes
- Treating watts as kWh.
- Entering 18.31 as dollars/kWh instead of cents/kWh.
- Using an old national average after the EIA table has moved.
- Assuming nameplate watts run continuously on a cycling appliance.
- Forgetting quantity or using 31 days for a 28-day bill.
- Adding a fixed charge on top of an all-in rate that already includes it.
- Assigning more peak hours than the appliance actually runs.
Frequently Asked Questions
How do I calculate electricity cost from watts?
kWh = (watts ÷ 1,000) × hours. Cost = kWh × $/kWh. Example: 1,000 W × 1 hour × $0.1831 = $0.18.
How much does 1 kWh cost in the US?
The EIA Electric Power Monthly Table 5.6.A residential US average for July 2026 (released September 24, 2026) is 18.31 cents/kWh. State averages ranged from 12.72 cents in Louisiana to 48.00 cents in Hawaii. Your utility tariff can differ.
How much does it cost to run a 1000 watt appliance for one hour?
1 kWh. At 18.31 cents/kWh that is about $0.18. At $0.18/kWh it is exactly $0.18.
How do I calculate electricity cost per month?
Monthly kWh = (watts ÷ 1,000) × hours/day × days/month × quantity × duty-cycle fraction. Monthly cost = monthly kWh × $/kWh.
How much does it cost to run a 1500 watt heater?
At 8 hours/day, 30 days, and $0.1831/kWh: 360 kWh and $65.92/month. Use the Space Heater Cost Calculator for seasonal heater-only estimates.
Does a refrigerator consume electricity 24 hours a day?
It is plugged in 24 hours, but the compressor cycles. A 150 W nameplate at a 33% duty cycle is closer to 50 W average. The duty-cycle field is for that.
How do I calculate the electricity cost of multiple appliances?
Add a row for each device, keep one shared rate, and read the combined monthly total. The highest-cost row is labeled in the results.
Where can I find my electricity rate?
On the utility bill, look for energy charge or price per kWh. An all-in rate is total amount due ÷ kWh. If you use that all-in rate, leave fixed charges at $0.
What is the difference between kW and kWh?
kW is power (how hard the appliance draws). kWh is energy (power × time). Bills charge energy.
How accurate is an electricity cost calculator?
It is as accurate as wattage, hours, duty cycle, and rate. It does not model every utility rider, demand charge, or tier automatically.
Can I calculate my electricity bill using kWh?
Yes. Use Electricity bill mode: monthly kWh × rate, plus optional fixed charges and tax.
Does the calculator include taxes and utility fees?
Only if you enter them. Appliance mode is energy cost. Bill mode can add a fixed charge and a tax percent. It does not invent fees.
Methodology, sources, and limits
- Formulas above. Display is rounded; internal math keeps extra precision.
- Residential rate presets: EIA Electric Power Monthly Table 5.6.A, July 2026, US average 18.31 cents/kWh.
- This page estimates energy cost in your browser. It is not a utility bill, rebate form, or solar-savings guarantee.