Electricity Calculator

Calculate electricity costs for any appliance based on power, usage, and rate.

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What Is the Electricity Calculator?

An electricity cost calculator turns wattage and runtime into dollars, exposing what appliances really cost to run. Every device draws watts; multiply by hours used to get watthours, divide by a thousand for kilowatthours, then multiply by your utility rate. The arithmetic is simple, but few people ever see it laid out, which is why space heaters, old fridges, and always on electronics quietly inflate bills. Use the tool to audit your home, decide when upgrading an appliance pays back, compare space heating against central heat, or check whether that gaming PC marathon is worth it. Knowledge here converts directly into a lower bill.

Key Statistics

Roughly 10,700 kWh

Annual electricity use of the average US home

Source: US Energy Information Administration
About 16 cents

Average residential price per kilowatthour nationally as of mid decade

Source: US EIA Electric Power Monthly
Near half

Share of home energy use consumed by space heating and cooling combined

Source: US EIA residential energy survey

The Formula

kWh per Day = (Watts x Hours per Day) / 1000. Total kWh = kWh per Day x Days. Total Cost = Total kWh x Rate per kWh.

Worked Examples

A 100-watt bulb on 24 hours daily for 30 days at $0.12 per kWh uses 72 kWh costing $8.64. A 1,500-watt space heater running 8 hours daily for 30 days draws 360 kWh at $43.20. Replacing with a 15-watt LED drops the bulb cost from $8.64 to just $1.30 per month.

Space heater evening habit

Heater draws 1,500 watts for 6 hours nightly
Daily energy is 9 kilowatthours
At $0.17 per kilowatthour the day costs $1.53

Thirty days of that habit adds about $45.90 to the bill.

Always on fan

A 75 watt fan runs 24 hours a day, using 1.8 kilowatthours daily
Monthly use is about 54 kilowatthours
Multiply by a $0.15 rate

Continuous comfort costs about $8.10 per month.

Real World Use Cases

Bill auditing

Rank your appliances by monthly cost to find the offenders driving up the bill.

Upgrade payback analysis

Compare an old fridge's draw against a new efficient model to compute payoff time.

Space heater decisions

Weigh supplemental electric heat against central options room by room.

Home office planning

Price out computers, monitors, and lighting running business hours all month.

Expert Tips

✓ Find the wattage on the appliance label or plug in a cheap power meter for measured truth.
✓ Rates vary hugely by state; pull your exact rate from the bill rather than using national averages.
✓ Phantom loads from chargers and standby electronics add up; smart strips cut them automatically.
✓ Heating and cooling dominate bills, so thermostat discipline beats gadget hunting every time.
✓ Time of use plans shift pricing by hour; run heavy loads off peak where the plan allows.

Frequently Asked Questions

How do I calculate electricity cost? ▼

Multiply wattage by hours used and divide by 1000 to get kilowatt hours, then multiply by your electricity rate. A 1000 watt space heater running 5 hours uses 5 kWh, and at 15 cents per kWh that costs 75 cents.

What is a kilowatt hour (kWh)? ▼

A kilowatt hour is the energy used by a 1000 watt device running for one hour. It is the unit your utility bills you for, so 1 kWh equals 1000 watts times 1 hour.

How do I convert watts to kilowatts? ▼

Divide watts by 1000. A 1500 watt appliance is 1.5 kilowatts. To find energy, multiply the kilowatts by the hours it runs to get kilowatt hours.

How much does it cost to run an appliance? ▼

Multiply the appliance wattage by hours used per day, divide by 1000, then multiply by your rate per kWh. Running a 200 watt TV for 4 hours daily is 0.8 kWh per day, roughly 12 cents at 15 cents per kWh.

What is the difference between watts and watt hours? ▼

Watts measure power, or how fast energy is used, while watt hours measure the total energy consumed over time. A 100 watt bulb draws 100 watts, but over 3 hours it uses 300 watt hours.

How do I estimate my monthly electricity bill? ▼

Estimate the daily energy use of each major appliance in kilowatt hours, multiply by your rate, and add them up for the month. Lighting, heating and cooling, and large appliances usually dominate the total.

How is electricity cost calculated? ▼

Multiply device watts by hours of use, divide by 1,000 to get kilowatthours, then multiply by your rate per kilowatthour.

Do old appliances really use much more power? ▼

Often yes, especially refrigerators built before modern efficiency standards, which can draw two to three times what a current model needs.

Common Mistakes to Avoid

⚠ Entering watts without dividing by 1000 to get kilowatts first (1500W = 1.5 kW for the kWh calculation).
⚠ Using peak surge wattage instead of running wattage for motor-driven appliances like refrigerators and AC units.
⚠ Assuming thermostat-controlled appliances run continuously when most cycle on and off throughout the day.
⚠ Confusing watts with kilowatthours. Watts describe instantaneous draw, while the bill charges for energy, meaning watts sustained over hours.

Last updated: 08-24-2026 · by CalculatorPro Tools

Electricity Calculator