The Simple Definition
A kilowatt hour (kWh) is a unit of energy equal to 1,000 watts of power used for one hour. It's how electricity companies measure and bill for the energy you consume.
1 kWh = 1,000 watts × 1 hour = the energy to run a 100W bulb for 10 hours
kW vs. kWh: What's the Difference?
This trips up a lot of people, but it's actually simple once you get it:
Kilowatt (kW) = Power
Measures how fast you're using electricity right now. Like the speedometer in your car.
Kilowatt Hour (kWh) = Energy
Measures total electricity used over time. Like the odometer (total miles driven).
The car analogy: kW is your speed (how fast). kWh is your distance traveled (how far). You pay for distance, not speed—that's why your bill shows kWh, not kW.
How to Calculate kWh
Here's the formula to calculate how many kilowatt hours an appliance uses:
kWh = (Watts × Hours Used) ÷ 1,000
Example 1: TV
A 200W TV watched for 4 hours: (200 × 4) ÷ 1,000 = 0.8 kWh
At 15¢/kWh, that's about 12 cents of electricity
Example 2: Space Heater
A 1,500W heater used for 3 hours: (1,500 × 3) ÷ 1,000 = 4.5 kWh
At 15¢/kWh, that's about 68 cents of electricity
Example 3: Central A/C
A 3,500W A/C running 8 hours: (3,500 × 8) ÷ 1,000 = 28 kWh
At 15¢/kWh, that's about $4.20 per day
What Can 1 kWh Power?
Here's what one kilowatt hour of electricity can do:
kWh
Run a 100W light bulb for 10 hours
kWh
Use a laptop computer for 20+ hours
kWh
Run a microwave oven for about 1 hour
kWh
Charge a smartphone 30-50 times
For Larger Amounts:
kWh
Run a central A/C for about 3 hours
kWh
Dry 3-4 loads of laundry
kWh
Run a refrigerator for about 1 month
kWh
Power an average U.S. home for ~1 month
How Many kWh Do Common Appliances Use?
Here's how much electricity typical household appliances use, based on average usage patterns:
| Appliance | Watts | Hrs/Day | kWh/Month | Cost/Month* |
|---|---|---|---|---|
| Central Air Conditioner | 3,500 | 8 | 840 | ~$126 |
| Electric Water Heater | 4,000 | 3 | 360 | ~$54 |
| Electric Dryer | 3,000 | 1 | 90 | ~$14 |
| Refrigerator | 150 | 24 | 108 | ~$16 |
| Desktop Computer | 200 | 8 | 48 | ~$7 |
| LED TV (55") | 80 | 5 | 12 | ~$2 |
| LED Light Bulb | 10 | 6 | 1.8 | ~$0.27 |
| Phone Charger | 5 | 3 | 0.45 | ~$0.07 |
*Estimated at 15¢/kWh (U.S. average)
How Your Electric Meter Measures kWh
Your electric meter tracks the cumulative kWh flowing into your home. Here's how it works:
Continuous Measurement
Your meter constantly measures the power (watts) flowing through it and multiplies by time to calculate kWh.
Monthly Reading
Your utility reads the meter (or uses a smart meter that reports automatically) and subtracts last month's reading to find your usage.
Bill Calculation
Your usage (kWh) is multiplied by your rate ($/kWh) to determine your energy charges. Additional fees for delivery and taxes are added.
Smart Meters
Modern smart meters record usage in 15-minute intervals, enabling time-of-use rates where electricity costs more during peak hours. This lets you save by running appliances during off-peak times.
How Much Does 1 kWh Cost?
Electricity prices vary significantly by location. Here's a snapshot of average rates:
16.9¢
U.S. Average
13-15¢
Texas*
25-30¢
California
22-28¢
New England
*In deregulated states like Texas, you can often find rates below the average by shopping for competitive plans.
Why kWh Rates Matter
A 5¢ difference in your rate adds up quickly. For a home using 1,000 kWh/month:
- At 12¢/kWh: $120/month
- At 17¢/kWh: $170/month
- Difference: $600/year
How to Reduce Your kWh Usage
HVAC (Biggest Saver)
- • Raise A/C to 78°F (each degree saves 3%)
- • Use ceiling fans (uses 10x less than A/C)
- • Change filters monthly
- • Seal air leaks around doors/windows
Lighting
- • Switch to LED bulbs (75% less energy)
- • Use natural light when possible
- • Install motion sensors/timers
- • Turn off lights when leaving rooms
Appliances
- • Unplug devices when not in use
- • Use smart power strips
- • Run dishwasher/laundry full loads only
- • Air dry clothes when weather permits
Water Heating
- • Lower water heater to 120°F
- • Use cold water for laundry
- • Take shorter showers
- • Insulate hot water pipes
Pay Less Per kWh
In deregulated states like Texas, Ohio, and Pennsylvania, you can shop for lower electricity rates. Enter your ZIP code to compare plans and see how much you could save.
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Frequently Asked Questions
What is 1 kWh equal to?
1 kWh equals 1,000 watts of power used for 1 hour. It's also equal to: 100 watts for 10 hours, 500 watts for 2 hours, or 2,000 watts for 30 minutes. In practical terms, 1 kWh can run a 100W light bulb for 10 hours, a laptop for about 20 hours, or a microwave for about 1 hour.
How much does 1 kWh cost?
The average U.S. electricity rate is about 16-17 cents per kWh. However, prices vary widely by state: Texas averages 13-15¢/kWh, California 25-30¢/kWh, and New England states 22-28¢/kWh. In deregulated markets, you can often find rates significantly below the average by shopping for a competitive energy plan.
How many kWh does a typical house use per month?
The average U.S. home uses about 900 kWh per month, but this varies significantly. Apartments typically use 400-600 kWh, average single-family homes use 800-1,200 kWh, and larger homes with electric heating or pools can use 2,000+ kWh. Climate is a major factor—homes in hot climates use more due to air conditioning.
What's the difference between kW and kWh?
kW (kilowatt) measures power—how fast you're using electricity at any moment. kWh (kilowatt hour) measures energy—the total electricity used over time. Think of kW as speed and kWh as distance. A 1,500W space heater uses 1.5 kW of power, and running it for 2 hours uses 3 kWh of energy.
How do I calculate kWh from watts?
To calculate kWh: multiply watts by hours used, then divide by 1,000. Formula: kWh = (Watts × Hours) ÷ 1,000. Example: A 100W TV watched for 5 hours = (100 × 5) ÷ 1,000 = 0.5 kWh. To find the cost, multiply kWh by your electricity rate.
Why is my electric bill measured in kWh?
Electricity is sold in kWh because it measures the actual energy delivered to your home over time—not just power capacity. This ensures you pay for what you actually use. Your meter tracks cumulative kWh, and your utility reads it monthly (or estimates) to calculate your bill.
How can I reduce my kWh usage?
The biggest kWh savers are: 1) Adjust thermostat 2-3 degrees (saves 5-10%), 2) Switch to LED bulbs (use 75% less than incandescent), 3) Unplug devices when not in use (saves phantom load), 4) Run major appliances during off-peak hours, 5) Upgrade old appliances to Energy Star models. A/C and heating typically offer the largest savings potential.
What appliances use the most kWh?
The biggest kWh consumers in most homes are: 1) Central air conditioning (3,000-5,000 kWh/year), 2) Electric water heater (2,500-4,500 kWh/year), 3) Electric dryer (1,800-5,000 kWh/year), 4) Refrigerator (400-800 kWh/year), 5) Electric oven (500-1,000 kWh/year). Space heaters and pool pumps can also be major consumers.
How We Ensure Accuracy
Since 2009, the team at ElectricRates.org has helped over 5 million energy consumers find better electricity rates. Supplier information comes from state regulators, company filings, and documented customer feedback. Read the editorial standards & see our methodology.