How do you convert watts to kWh?

Multiply watts by hours of use, then divide by 1,000. Formula: kWh = (Watts × Hours) ÷ 1,000. Example: a 1,500W appliance running 8 hours = 12 kWh per day.

What is the difference between watts and kWh?

Watts measure power (rate of energy use at an instant). kWh measures energy (total electricity consumed over time). Your electric bill charges for kWh. Think of watts as speed and kWh as distance.

Watts to kWh Calculator

Convert watts to kilowatt-hours instantly. Enter wattage and daily use — get energy consumption and electricity cost.

Appliance details

Power draw?

Hours used per day?

hrs/day

Electricity rate?

Energy consumption

12.000 kWh per day

Monthly kWh365.3 kWh

Annual kWh4,380 kWh

Daily cost$1.800

Monthly cost$54.79

Annual cost$657.00

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How to Use This Calculator

Enter the wattage

Input the device's power consumption in watts (W). You can find this on the label on the bottom or back of the appliance, in the owner's manual, or on the product specifications page. Common values: LED bulb 8-12W, laptop 30-65W, TV 55-200W, air conditioner 750-3500W, electric heater 1000-1500W.

Set daily usage hours

Enter how many hours per day the device is running. For devices that run continuously like a refrigerator, enter 24. For intermittent devices, estimate the average on-time. A refrigerator's compressor cycles on about 30-40% of the time, so a 400W rated fridge has an effective draw closer to 150W continuously — or you can use 400W at 10 hours/day.

Use the appliance presets

Click a preset button — LED bulb, Refrigerator, Air conditioner, or EV charger — to instantly calculate energy costs for those common devices. Adjust the values to match your specific appliance.

Select your electricity rate

Choose your electricity rate to see cost calculations. The US average is about $0.15/kWh, but it varies from $0.10 (some southern states) to $0.35+ (Hawaii, California). Check your utility bill for your exact rate.

The Formula

Daily kWh = Watts × Hours per day ÷ 1,000 Monthly kWh = Daily kWh × 30.44 Annual kWh = Daily kWh × 365 Daily cost = Daily kWh × Electricity rate ($/kWh) Monthly cost = Monthly kWh × Rate Annual cost = Annual kWh × Rate

The division by 1,000 converts watts to kilowatts (kW). One kilowatt-hour (kWh) is the energy consumed by a 1,000-watt device running for 1 hour. Your electricity bill charges by kWh — so this conversion is the key to understanding what any device actually costs to run.

Example

Central air conditioner — summer cooling season

A 1,500W central air conditioner running 8 hours per day during a 4-month summer. Electricity rate $0.15/kWh.

Wattage1,500 W

Hours per day8 hours

Electricity rate$0.15/kWh

Result

Daily energy12 kWh/day

Monthly energy365 kWh/month

Daily cost$1.80/day

Monthly cost$54.75/month

Running the AC for 4 summer months costs about $219. A solar system that produces 12 kWh/day would completely offset this usage — roughly a 3 kW array in a sunny location.

Common Appliance Wattages

LED light bulb8–12 W

Laptop computer30–65 W

Desktop computer100–300 W

55" LED TV50–100 W

Refrigerator100–200 W avg

Dishwasher1,200–2,400 W

Clothes washer500–1,000 W

Electric dryer4,000–6,000 W

Electric oven2,000–5,000 W

Air conditioner (window)500–1,500 W

Air conditioner (central)3,000–5,000 W

Electric water heater4,000–5,500 W

EV charger (Level 2)7,200–11,500 W

FAQ

What is the difference between watts and kilowatt-hours? ▼

Watts (W) measure power — the rate of energy flow at a given instant. Kilowatt-hours (kWh) measure energy — the total amount of electricity consumed over time. A 1,000W device running for 1 hour uses 1 kWh. Your electricity bill charges for kWh (total energy), not watts (instantaneous power). Think of watts like speed and kWh like distance — one tells you how fast you're going, the other tells you how far you've traveled.

How do I find the wattage of an appliance? ▼

Check the nameplate label on the back or bottom of the appliance — it lists the rated wattage. For devices that vary in power draw (like a laptop that uses more when gaming), the label shows the maximum. You can also use a plug-in energy monitor (like a Kill-A-Watt meter, ~$25) to measure actual real-time and accumulated consumption. For solar sizing purposes, use rated watts for worst-case planning.

Why does my electricity bill show kWh but my appliances show watts? ▼

Appliances are rated in watts because that tells you their power requirement — useful for sizing circuits, fuses, and inverters. Your utility bills in kWh because that's the accumulated energy you actually consumed over the billing period. The conversion is simple: multiply watts by hours of use and divide by 1,000 to get kWh. This calculator does that math for you.

How many kWh does a typical US home use per day? ▼

The US average household uses about 29.6 kWh per day (10,800 kWh/year according to EIA). This varies widely by region: homes in Louisiana average 40+ kWh/day due to AC use, while Hawaii homes average under 20 kWh/day due to mild climate and high electricity costs driving conservation. Your solar system needs to produce enough daily kWh to cover this consumption.