The short answer
A kilowatt-hour (kWh) is 1,000 watts running for 1 hour — the standard billing unit for electricity. A 100W bulb burning 10 hours uses 1 kWh. Typical US homes use 800-1,200 kWh/month at an average $0.13/kWh = $104-$156. Converting: 1 kWh = 3,412 BTU = 0.034 therms.
A kilowatt-hour (kWh) is the unit electricity is sold in. One kWh = 1,000 watts running for 1 hour. A 100W lightbulb burning for 10 hours uses 1 kWh. A typical US household uses 800-1,200 kWh/month. At $0.13/kWh average, that's $104-$156/month. Understanding the kWh — and how to convert it to and from watts, BTUs, and therms — is the foundation of every other energy decision.
kWh definition
Watts (W) measure instantaneous power — how fast something uses energy. A 100W bulb consumes 100 joules of energy per second.
Kilowatt-hours (kWh) measure energy over time — how much was used. 100W x 1 hour = 0.1 kWh. 100W x 10 hours = 1 kWh.
Your electric meter measures kWh, not watts. The bill is kWh x rate ($/kWh).
Common kWh consumption
Refrigerator: 50-80 kWh/month.
Window AC (5,000 BTU): 30-100 kWh/month seasonal.
Central AC (3-ton): 200-600 kWh/month seasonal.
Electric water heater: 300-500 kWh/month.
Electric oven: 30-60 kWh/month.
EV charging (100 mi/week): 100-130 kWh/month.
Lighting (10 LED bulbs, 5 hrs/day): 13-20 kWh/month.
Unit conversions for cross-comparison
1 kWh equals 3,412 BTU. Useful when comparing electric heat (billed in kWh) to gas heat (billed in therms or BTU). The same heat output costs different amounts depending on the fuel source and the per-unit price of each.
1 therm equals 100,000 BTU equals 29.3 kWh equivalent. So 1 therm of natural gas at $1.50 delivers the same heat as 29.3 kWh of electric resistance at $0.05 per kWh ($1.47). Heat pumps invert the comparison because they deliver 2 to 4 kWh equivalent of heat per 1 kWh of electricity consumed.
1 gallon of gasoline equals 33.7 kWh equivalent. EPA uses this for EV miles-per-gallon-equivalent (MPGe) labels. So an EV at 30 kWh per 100 miles has roughly 112 MPGe (33.7 / 30 times 100).
1 ton of cooling equals 12,000 BTU per hour equals 3.5 kW. Air conditioner sizing is in tons. A 3-ton AC uses approximately 3.5 kW when running, which equals 35 kWh over a 10-hour run — about $4.55 at $0.13 per kWh.
How kWh interacts with your rate plan
Most US residential customers pay a flat per-kWh rate that does not vary by time of day or month. Some utilities offer time-of-use (TOU) plans where the per-kWh rate changes by hour or season — typically 2 to 4 times more expensive during weekday afternoon peak hours, and significantly cheaper overnight and weekends. The time-of-use-rate-vs-flat-rate guide breaks down the trade-off.
For households on TOU, the kWh meter is supplemented by an hourly read — the bill shows kWh consumed in each rate period multiplied by that period rate. Most utility portals visualize this as a stacked bar chart per day. Smart-meter customers can verify the calculation against their own interval data.
Demand charges (more common for commercial than residential) add a separate billed component based on peak kW (instantaneous power) rather than kWh (energy over time). A facility that pulls 50 kW peak for 5 minutes pays the same demand charge as one that pulls 50 kW peak for 5 hours, even though the second uses 60 times more kWh. The demand-charge-strategy guide covers commercial demand-charge management.
Infographic
kWh consumption pattern — flat rate vs TOU rate
Reducing kWh through efficiency moves
Once you understand kWh, every efficiency move becomes a kWh-reduction calculation. Replacing a 100W incandescent bulb burning 5 hours per day with a 10W LED saves 0.45 kWh per day or 13.5 kWh per month — about $1.75 per bulb per month at $0.13 per kWh. A house with 20 such bulbs saves $35 per month from LED replacement alone.
Lowering the thermostat 4F in winter cuts furnace runtime roughly 12 percent, which translates directly to gas therm reduction (and kWh reduction for households on electric heat or heat pumps). A typical electric-heat household using 800 kWh per month for heating saves 96 kWh per month at the lower setpoint — about $12 at $0.13 per kWh.
Replacing a 1996-era refrigerator (1,400 kWh per year) with a modern Energy Star model (350 kWh per year) saves 1,050 kWh per year — $137 at $0.13 per kWh. The how-to-lower-your-electric-bill guide covers the full ROI ladder.
Recap
Bottom line
The kilowatt-hour is the foundational unit of every electricity bill in the United States — 1,000 watts running for 1 hour. Every appliance, every rate plan, every efficiency move ultimately maps back to kWh: how much you consume, when you consume it, and the per-kWh rate you pay. A typical US home uses 800 to 1,200 kWh per month at an average rate of $0.13 per kWh, producing $104 to $156 monthly bills.
Understanding the kWh-watt relationship and the unit conversions to BTU, therms, and gasoline equivalent gives you the foundation for every cross-fuel comparison (gas vs electric heating, EV vs gas-car fuel cost, heat pump vs furnace operating cost). The how-to-read-your-electricity-bill, how-to-read-your-electric-meter, and how-to-lower-your-electric-bill guides build on this foundation.
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