Key Takeaways
- Electricity cost = (Watts x Hours) / 1000 x Rate per kWh
- The average US electricity rate is $0.13 per kWh
- LED bulbs use 75-80% less energy than incandescent
- Phantom loads from standby devices can add $100-200/year
- Air conditioning typically accounts for 12% of annual energy costs
What Is a Kilowatt-Hour (kWh)?
A kilowatt-hour (kWh) is the standard unit for measuring electricity consumption. It represents the energy used by a 1,000-watt appliance running for one hour. Your electricity bill charges you based on how many kWh you consume each month.
For example, if you run a 100-watt light bulb for 10 hours, you use 1 kWh of electricity (100W x 10 hours = 1,000 Wh = 1 kWh).
The Electricity Cost Formula
Cost = (Watts x Hours) / 1000 x Rate
Example: 60W Light Bulb at $0.13/kWh
Common Appliance Wattages
Knowing the typical wattage of household appliances helps you estimate costs:
| Appliance | Typical Wattage | Daily Cost (8 hrs) |
|---|---|---|
| LED Light Bulb | 10W | $0.01 |
| Laptop | 50W | $0.05 |
| Television (LED) | 100W | $0.10 |
| Refrigerator | 150W | $0.16 |
| Desktop Computer | 200W | $0.21 |
| Space Heater | 1500W | $1.56 |
| Window AC | 1200W | $1.25 |
| Electric Dryer | 3000W | $3.12 |
Pro Tip: Find Your Wattage
Check the label on your appliance or the owner's manual for the exact wattage. For devices with variable power draw (like refrigerators), use the "average" or "running" wattage, not the peak/startup wattage.
5 Ways to Reduce Electricity Costs
- Switch to LED bulbs - Uses 75% less energy than incandescent
- Unplug phantom loads - Devices on standby still use power
- Use smart power strips - Automatically cut power to idle devices
- Upgrade to Energy Star appliances - 10-50% more efficient
- Adjust thermostat - Each degree saves 3% on heating/cooling
Frequently Asked Questions
Check your electricity bill for the "rate" or "price per kWh." It's usually listed in the summary section. The US average is about $0.13/kWh, but rates vary significantly by state - from $0.08 in Louisiana to $0.35+ in Hawaii.
The biggest electricity users are typically: 1) Heating/cooling (40-50%), 2) Water heating (14-18%), 3) Appliances like washers/dryers (13%), 4) Lighting (9-12%), and 5) Electronics/computers (4-6%).
Yes! This is called "phantom load" or "vampire power." Devices like chargers, TVs on standby, and gaming consoles can use 5-10W even when "off." This can add $100-200 to your annual electricity bill. Use smart power strips to eliminate phantom loads.
A typical 1500W space heater running 8 hours/day at $0.13/kWh costs about $1.56/day or $47/month. Over a winter season (4 months), that's nearly $190. It's often cheaper to use central heating for the whole house than space heaters in multiple rooms.
A kilowatt (kW) is simply 1,000 watts. We use kilowatts for larger measurements because the numbers are easier to work with. Your electricity bill uses kilowatt-hours (kWh) to measure consumption. 1 kWh = 1,000 watts used for 1 hour.