Electricity cost calculator,
wattage to dollars.

Field guide

Understanding electricity usage, kWh, and your electric bill.

Every device in your home consumes electricity measured in watts (W) or kilowatts (kW). Multiply the power draw by the time the device runs and you get energy consumption in kilowatt-hours (kWh): the unit your utility company charges you for.

The fundamental formula

The core calculation is straightforward:

• kWh = Watts × Hours ÷ 1,000
• Cost = kWh × Rate ($/kWh)

For example, a 1,500 W space heater running for 8 hours consumes 1,500 × 8 ÷ 1,000 = 12 kWh. At the US national average rate of $0.13/kWh, that's $1.56 per day.

Watts vs. kilowatts

The difference is simply a factor of 1,000. Small appliances like phone chargers (5 W) and LED bulbs (10 W) are most naturally expressed in watts. Large appliances like electric dryers (5,000 W) and EV chargers (7,200 W) are more readable in kilowatts (5 kW and 7.2 kW). Both units are equivalent. This calculator accepts either.

Average appliance wattages

Power draw varies significantly between device categories:

Note that the refrigerator's compressor cycles on and off — actual draw averages around 150 W over 24 hours, not a continuous 150 W full-blast.

How electricity rates work

Your utility rate (in cents or dollars per kWh) is the price you pay for each kilowatt-hour consumed. Rates vary widely:

• US national average: ~$0.13/kWh (ranges from $0.10/kWh in states like Louisiana to $0.30+/kWh in Hawaii and California).
• Time-of-use (TOU) rates: Many utilities charge more during peak hours (typically 4–9 PM) and less at night. If you have TOU pricing, run high-wattage appliances (laundry, EV charging) during off-peak hours.
• Tiered rates: Some utilities charge a lower rate for the first block of kWh each month and a higher rate once you exceed a baseline. Heavy users effectively pay a blended rate higher than the advertised base.

Find your actual rate on your electric bill under "kWh charges" or "energy charge." Divide the total energy charge by the total kWh consumed for your effective rate.

CO₂ emissions from electricity

Burning fossil fuels to generate electricity releases carbon dioxide. The US EPA estimates a national grid average of approximately 0.386 kg CO₂ per kWh (386 g/kWh). This figure represents a blend of coal, natural gas, nuclear, and renewables across the US grid.

Your actual emissions depend on your utility's energy mix. If your utility is heavily renewable (hydro, wind, solar), your per-kWh emissions are much lower. If it's coal-heavy, they may be higher. The EPA publishes regional emissions factors for more precise estimates.

The average US household uses 887 kWh/month

According to the US Energy Information Administration (EIA), the average American household consumes about 887 kWh per month (10,632 kWh/year), costing roughly $115/month at national average rates. This calculator shows how any single device compares to that total, helping you identify your biggest energy consumers.

Heating and cooling typically account for the largest share (~45%) of home energy use, followed by water heating (~18%) and appliances/lighting (~35%). An electric vehicle charger, run nightly, can easily add 200–300 kWh/month — a 25–35% increase to your bill.

How to reduce your electricity bill

• Switch to LEDs. Replacing a 60 W incandescent with a 10 W LED cuts lighting energy by 83%. Across 10 bulbs used 4 hours/day, that saves ~70 kWh/month.
• Use smart power strips. Devices in standby mode ("vampire load") still draw 1–5 W each. A TV, game console, and sound bar together can waste $15–$30/year doing nothing.
• Run laundry and dishwashers at night. On time-of-use plans, off-peak rates can be 50–70% cheaper than peak hours.
• Set your thermostat wisely. Every 1°F you raise your AC setpoint saves roughly 1–3% on cooling costs. A programmable thermostat that raises the temperature while you're at work can save $100+/year.
• Audit your refrigerator and freezer. Old refrigerators from the 1990s can consume 3–4× more energy than modern Energy Star models. If yours is 15+ years old, replacing it may pay for itself within a few years.

Using this calculator effectively

The most common use case is identifying expensive-to-run appliances. Enter each major device, set realistic usage hours, and sort by monthly cost. A few typical discoveries:

• An electric space heater run 8 hours/day all winter can cost $45–$75/month, more than your entire base bill.
• An EV charged 2 hours/night at 7.2 kW adds ~$28/month at $0.13/kWh, far cheaper than gasoline.
• A gaming PC running 6 hours/day costs ~$4–$8/month, similar to leaving a single incandescent bulb on 24/7.

For the most accurate results, check the actual wattage on the device label or in the manual — appliance databases use typical averages, but real-world draw varies by model, age, and usage intensity.