kWh Calculator

Enter watts and hours — get daily kWh, monthly kWh, and electricity cost instantly.

Appliance details

Wattage?

Hours per day?

hrs/day

Electricity rate?

$/kWh

Energy consumption

4.000 kWh per day

Monthly kWh120.00 kWh

Annual kWh1,460.0 kWh

Monthly cost$18.00

Annual cost$219

Solar panels to offset3 × 400W panels

1,460 kWh/yr is equivalent to running 146,000 LED bulbs for 1 hour, or 417 miles of EV driving (at 3.5 mi/kWh).

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How to Use This Calculator

Enter watts and hours

The two inputs that determine energy use: wattage (from the appliance label) and hours per day of operation. The kWh result updates instantly. For appliances with variable loads (refrigerators, air conditioners), use the average watts, not peak watts. A fridge labeled 200W runs its compressor at that rating but cycles on and off — its average draw might be 60-80W.

Add your electricity rate

Enter your electricity rate to see daily, monthly, and annual costs. US average is $0.15/kWh but ranges from $0.10 (Louisiana) to $0.35+ (California peak tier, Hawaii). Use the Electricity Cost Calculator to find your exact effective rate from your utility bill.

Solar context

The result shows how many 400W solar panels would be needed to produce enough electricity to offset this appliance's annual usage. This puts consumption in solar terms — a 5,000W electric dryer running 30 minutes per day requires about 1 entire 400W solar panel just for that single appliance.

The Formula

Daily kWh = Watts ÷ 1,000 × Hours per day Monthly kWh = Daily kWh × 30 Annual kWh = Daily kWh × 365 Daily cost = Daily kWh × Rate ($/kWh) Monthly cost = Monthly kWh × Rate Annual cost = Annual kWh × Rate Solar panels to offset = Annual kWh ÷ (Peak Sun Hours × Efficiency × 365) ÷ Panel Watts

The kWh unit is kilowatt-hour — equal to 1,000 watts running for one hour. A 100W light bulb running for 10 hours uses 1 kWh. This is the unit utilities charge for and the unit that defines solar production.

Example

Cost comparison: old vs. LED bulbs

Replacing ten 60W incandescent bulbs with ten 10W LED bulbs. Both sets run 5 hours per day at $0.15/kWh.

10 × 60W bulbs daily3.0 kWh/day

10 × 10W LED daily0.5 kWh/day

Monthly savings75 kWh = $11.25/mo

Annual savings912 kWh = $136.80/yr

The LED switch saves $137/year in electricity and reduces the solar system needed for lighting from 0.8 kW to 0.13 kW — a difference of nearly 2 × 400W panels. LED replacement is the easiest energy reduction before solar installation.

FAQ

What is a kilowatt-hour (kWh)? ▼

A kilowatt-hour is a unit of energy equal to 1,000 watts running for one hour. Examples: a 1,000W microwave running for 1 hour uses 1 kWh. A 100W light bulb running for 10 hours uses 1 kWh. A 3,000W air conditioner running for 20 minutes uses 1 kWh. Your utility charges you per kWh — typically $0.10-0.35 depending on location.

What's the difference between watts and kWh? ▼

Watts measure power — the rate of energy use at an instant in time. kWh measures energy — the total amount consumed over time. Analogy: watts are like speed (mph), kWh are like distance (miles). A 60W bulb running for 2 hours uses the same energy as a 120W bulb running for 1 hour: 120 Wh = 0.12 kWh.

How many kWh does a house use per month? ▼

US average: 899 kWh/month (EIA 2023 data). By region: South (1,100-1,300 kWh, high AC use), Midwest (700-900 kWh), Northeast (600-750 kWh), West (600-800 kWh). All-electric homes with EV charging can exceed 2,000 kWh/month. Very efficient homes with heat pumps and LED lighting can get below 400 kWh/month.

How do I convert amps to watts? ▼

Watts = Amps × Volts. For standard US household outlets: 120V × amps = watts. For 240V appliances (dryers, EV chargers): 240V × amps = watts. Example: a coffee maker drawing 10A at 120V = 1,200W. An EV charger drawing 30A at 240V = 7,200W. Many appliance labels show amps instead of watts — use this formula to convert.

How much does 1 kWh cost? ▼

US average residential rate: approximately $0.15/kWh in 2026. Cheapest states: Louisiana ($0.10), Idaho ($0.11), Washington ($0.11). Most expensive: Hawaii ($0.40+), California (tiered, averaging $0.30+), Massachusetts ($0.22). To find your exact rate, divide your monthly bill by the kWh used (subtract any fixed charges first for an accurate variable rate).