What is a kilowatt-hour (kWh)? A simple explanation

By kWhCompare · Updated October 13, 2026 · 5 min read

A kilowatt-hour (kWh) is the amount of energy it takes to run a 1,000-watt appliance for one hour. It's the unit your utility uses to measure and bill your electricity use. For example, running a 1,500-watt space heater for 4 hours uses 6 kWh, which costs about $1.10 at the U.S. average rate of 18.34 cents per kWh.

What is a kilowatt-hour?

A kilowatt-hour is a unit of energy, not power. It represents the total amount of electricity used over time, which is exactly what shows up as a charge on your electric bill. Every appliance in your home, from a phone charger to a central air conditioner, uses energy measured in kWh, and your utility adds it all up each month to calculate what you owe.

Understanding kWh matters because it's the one number that connects your appliances, your usage habits, and your actual dollar cost. Once it clicks, you can estimate the cost of running almost anything, spot which appliances are quietly driving your bill up, and compare electricity rates between plans or states on equal footing.

Watts vs. kilowatt-hours: what's the difference

A watt measures the rate at which a device draws power at any given instant, similar to how a speedometer shows how fast a car is moving right now. A kilowatt (kW) is simply 1,000 watts. Neither a watt nor a kilowatt tells you anything about total energy use or cost by itself, because that depends on how long the device actually runs.

A kilowatt-hour adds the missing piece: time. Run a 1,000-watt appliance for one hour and you've used 1 kWh. Run a 100-watt appliance for 10 hours and you've also used 1 kWh. Same total energy, completely different wattage and runtime.

Common mix-up: kW vs kWh

People often use kilowatts and kilowatt-hours interchangeably, but they measure different things. A 5 kW solar system describes how much power it can produce at peak output. The kWh it generates over a day, a month, or a year describes the actual energy delivered, and that's the number that offsets your bill or shows up as usage.

How to calculate kilowatt-hours and cost, step by step

You can estimate exactly how much any appliance costs to run with one formula:

kWh used = (watts divided by 1,000) multiplied by hours used

Multiply the result by your rate per kWh to get the dollar cost. Here's a full worked example using a 1,500-watt space heater running 4 hours a day for a 30-day month.

1. Convert watts to kilowatts. 1,500 watts divided by 1,000 equals 1.5 kW.
2. Multiply by hours used per day. 1.5 kW times 4 hours equals 6 kWh per day.
3. Multiply by days in the month. 6 kWh times 30 days equals 180 kWh for the month.
4. Multiply by your rate. At the U.S. average residential rate of 18.34 cents per kWh, that's 180 times $0.1834, or $33.01, just for that one heater.

Electricity rates vary a lot by state, so the same heater costs less in Texas, where the average rate is 15.94 cents per kWh: 180 kWh times $0.1594 equals $28.69 a month. Check current Texas electricity rates or your own state's page and plug in your actual rate to get a precise number.

Everyday appliances: how many kWh they use

Once you know the formula, you can estimate the energy use of almost anything in your house. The table below shows typical ranges for common appliances, priced at the U.S. average rate of 18.34 cents per kWh.

Notice how much the window AC unit and the refrigerator dwarf small electronics. A refrigerator running all day can use more energy than a dozen phone chargers combined, even though it feels less noticeable because it's not something you turn on and off. For a full breakdown of total household energy use, see how many kWh a house uses per month.

How to find kWh usage on your electric bill

Every residential electric bill in the U.S. reports your total kWh used for the billing period, usually near the top of the bill or in a usage summary box. Look for a line labeled something like "kWh used," "energy charge," or "usage this period." Many bills also show a graph comparing your usage to the same month last year, which is a quick way to spot a spike.

Your bill multiplies that kWh figure by your per-kWh rate to calculate the energy charge, then typically adds delivery charges, fixed monthly fees, and sometimes taxes on top. If you want a full line-by-line walkthrough of what each charge means, see our electric bill breakdown. Texas residents on a retail plan can also check their Electricity Facts Label, which lists the average price per kWh at 500, 1,000, and 2,000 kWh of usage so you can compare plans honestly.

Why your kWh rate varies so much by state

Not every state pays the same price per kWh, and the gap is bigger than most people expect. The U.S. average residential rate is 18.34 cents per kWh, but that masks huge regional swings driven by fuel mix, grid infrastructure, climate, and whether the state has a deregulated retail market.

Hawaii residents pay the most in the country at 52.72 cents per kWh, largely because the state depends heavily on imported fuel. California follows at 34.74 cents per kWh. On the other end, states like Nevada (13.11 cents), Nebraska (13.25 cents), and Utah (13.37 cents) sit well below the national average. Texas, at 15.94 cents per kWh, sits below the U.S. average thanks in part to its competitive retail electricity market, where households can shop among providers. You can browse rates for any state on our electricity rate comparison tool, or dig into what counts as a fair price with our guide on what is a good price per kWh.

How to use kWh to lower your electric bill

Once you understand kWh, you can target the appliances that matter most instead of guessing. Heating and cooling almost always dominate a home's energy use, so small changes there have an outsized effect on your total kWh and your bill.

• Check appliance wattage labels and use the kWh formula to find your biggest energy users, usually AC, heating, water heaters, and dryers.
• Shift high-wattage tasks like laundry and dishwashing to off-peak hours if your plan has time-of-use pricing.
• Seal drafts and adjust your thermostat a few degrees to cut heating and cooling kWh, especially in extreme seasons. See our seasonal guides on lowering your bill in summer and lowering your bill in winter.
• If your usage looks unusually high for no clear reason, read through why your electric bill might be so high to rule out common causes.

What to do next

Start by finding the total kWh used on your last bill and dividing your energy charge by that number to see your actual rate per kWh. Then compare that rate to your state's average using our free electricity rate comparison tool, and if you're in a deregulated market like Texas, check whether switching plans could lower your per-kWh price without changing your usage habits at all.

Frequently asked questions

Sources

• U.S. Energy Information Administration, Electric Power Monthly (eia.gov)
• Public Utility Commission of Texas, rate and market rules (puc.texas.gov)

Figures are checked against these sources when each guide is updated. See how we research and calculate. This guide is for general information and isn't financial advice.