Electricity Cost Calculator

1. Enter the wattage of your appliance. Look for the "W" rating on the device label or manual.
2. Enter the hours per day the appliance typically runs.
3. Set your electricity rate in dollars per kWh. The default is $0.16 (approximate US average). Check your utility bill for your actual rate.
4. Choose the billing period: daily, weekly, monthly (30 days) or annual (365 days).
5. Read the cost and kWh used for your chosen period, plus the annual totals.

An electricity cost calculator converts an appliance's power rating and running time into a dollar amount. It answers one of the most common household questions: how much does it cost to run this device?

Every electrical appliance draws power measured in watts. When you run it for a certain number of hours the energy consumed is measured in kilowatt-hours (kWh). Your utility company charges you a price per kWh, so multiplying the kWh by that price gives the running cost.

This is especially useful for comparing appliances, deciding whether to upgrade to a more efficient model, or understanding which devices drive your monthly electricity bill. For related energy tools, see the solar panel calculator and the EV charging cost calculator.

The calculator uses a single, well-known formula from electrical engineering.

1. Multiply the appliance wattage by the hours it runs each day.
2. Multiply by the number of days in the billing period.
3. Divide by 1,000 to convert watt-hours to kilowatt-hours.
4. Multiply the kWh by your electricity rate to get the cost.

Why Divide by 1,000?

One kilowatt is 1,000 watts. Utility companies bill in kilowatt-hours, not watt-hours, so the division converts the units to match your bill.

Example 1: 100 W Light Bulb

A 100-watt bulb runs 8 hours per day for 30 days at $0.16/kWh.

Energy: 100 x 8 x 30 / 1,000 = 24 kWh per month.

Monthly cost: 24 x $0.16 = $3.84.

Annual cost: 24 x 12 = 288 kWh/year; 288 x $0.16 = $46.08/year.

Example 2: 1,500 W Space Heater

A 1,500-watt space heater runs 6 hours per day for 30 days at $0.16/kWh.

Energy: 1,500 x 6 x 30 / 1,000 = 270 kWh per month.

Monthly cost: 270 x $0.16 = $43.20.

The heater uses more than ten times the energy of the light bulb because its wattage is 15 times higher, partly offset by fewer running hours.

If you are not sure of your appliance wattage, this table lists typical values. Actual wattage varies by model.

For cycling appliances like refrigerators and air conditioners, the actual duty cycle is lower than the listed hours. Use the average running hours, not 24 hours, for a realistic estimate.

Your electricity bill shows how many kWh you used and the rate per kWh. Some utilities use tiered pricing where the rate goes up as you use more. Others use time-of-use pricing with different rates for peak and off-peak hours.

Finding Your Rate

Look for the line labelled "energy charge" or "price per kWh" on your bill. Divide the total energy charge by the total kWh used if the per-kWh rate is not shown directly. The default $0.16/kWh in this calculator is a rough US national average; your actual rate may differ.

Additional Charges

Many bills include fixed service fees, demand charges, fuel surcharges and taxes that are not captured by a simple kWh calculation. This calculator estimates the energy cost only, not the full bill amount.

Switch to LED Lighting

A 10 W LED replaces a 60 W incandescent bulb, cutting lighting energy by more than 80 percent.

Unplug Standby Devices

Electronics in standby mode still draw power. A power strip makes it easy to cut all standby draws at once.

Use a Programmable Thermostat

Heating and cooling are the largest electricity costs in most homes. Scheduling temperatures around your routine saves energy.

Run Large Appliances Off-peak

If your utility uses time-of-use pricing, running the dishwasher or laundry at night can lower the effective rate.

Consider Solar

Rooftop solar panels can offset some or all of your electricity consumption. Use the solar panel calculator to estimate potential savings.

Watts (W)

A watt is a unit of power, which is the rate at which energy is used. A 100 W bulb uses energy at the rate of 100 watts.

Kilowatts (kW)

One kilowatt is 1,000 watts. It is a more convenient unit for larger appliances and for billing.

Kilowatt-hours (kWh)

A kilowatt-hour is the amount of energy used when a 1 kW device runs for one hour. It is the billing unit on your electricity bill. A 100 W bulb running for 10 hours uses 1 kWh.

Why KWh Matters

Your utility company does not charge for watts; it charges for kilowatt-hours. Watts tell you how fast energy is used; kWh tells you how much total energy was consumed over time.

Comparing Appliances

Before buying a new air conditioner or heater, enter the wattage of each model to see which one costs less to run.

Budgeting Utility Bills

Add up the costs of your main appliances to estimate next month's electricity bill.

Evaluating Energy Upgrades

Calculate how much you save by switching from incandescent bulbs to LEDs or from an old AC to an efficient model.

Understanding Standby Costs

Even small wattages add up over 24 hours. A 5 W charger left plugged in all day uses about 3.6 kWh per month.

For travel fuel costs, try the fuel cost calculator.

1. Using the Wrong Wattage

The number on the box may be peak wattage, not average. Look for the rated or typical wattage for a better estimate.

2. Ignoring Cycling Appliances

A refrigerator does not run its compressor 24 hours a day. Use the estimated average running hours, not the hours it is plugged in.

3. Forgetting About Standby Power

Devices in standby still draw a few watts. Over a year, standby power can cost $50 to $100 across all devices in a home.

4. Using the Wrong Rate

The default $0.16 is a rough US average. Your local rate may be half or double that. Always check your bill.

5. Overlooking Non-energy Charges

Fixed fees, demand charges and taxes add to your bill beyond the kWh cost. This calculator shows energy cost only.

The math is exact: watts times hours times days divided by 1,000 times the rate. The accuracy of the result depends entirely on the inputs you provide.

Multiply the appliance wattage by hours per day by the number of days, divide by 1,000 to get kWh, then multiply by your rate per kWh. For example, 100 W x 8 hours x 30 days / 1,000 = 24 kWh; 24 x $0.16 = $3.84 per month.

A kilowatt-hour (kWh) is the energy used when a 1,000-watt device runs for one hour. It is the standard billing unit on residential electricity bills.

At $0.16/kWh for 6 hours a day over 30 days, a 1,500 W heater uses 270 kWh and costs about $43.20 per month.

As of recent data the US national average is roughly $0.16 per kWh, but rates vary widely by state and utility. Check your bill for your actual rate.

Your bill includes fixed service charges, taxes, demand charges and sometimes tiered pricing. This calculator estimates the energy cost only, not the full bill.

A typical modern refrigerator uses 100 to 400 watts but cycles on and off. Average running time is about 8 to 12 hours per day, so actual daily use is roughly 1 to 4 kWh.

Individual standby loads are small (2 to 10 watts), but across many devices running 24 hours a day the total can reach 50 to 100 dollars per year.

Switch to LED bulbs, unplug standby devices, use a programmable thermostat, and run large appliances during off-peak hours if your utility offers time-of-use rates.

It calculates consumption accurately but does not subtract solar generation. Pair it with a solar panel calculator to see net usage.

Run the calculator once per appliance and add up the costs. Each device has its own wattage and typical running hours.

• Electrical power and energy fundamentals (P = W x t) (Khan Academy; power, energy, and kilowatt-hour definitions).
• US Energy Information Administration - electricity data (EIA; average US residential electricity rates and consumption data).
• ENERGY STAR appliance reference (US EPA / DOE program for energy-efficient appliances and wattage benchmarks).