How do you convert watts to kWh?
Multiply the watts by the number of hours the device runs, then divide by 1,000. kWh = (watts times hours) divided by 1,000. It is easier in two steps. First get watt-hours: Wh = watts times hours. Then divide by 1,000 to get kWh. A 1,500 watt space heater running for 8 hours is 1,500 times 8, or 12,000 watt-hours, divided by 1,000 for 12 kWh. A 60 watt bulb left on for 5 hours is 300 watt-hours, or 0.3 kWh.
The number you almost always have to supply yourself is the hours, because it is not printed on anything. A device's wattage is on its label or nameplate, but how long you run it is up to you, and that is the whole reason watts alone cannot give you kWh. If the split between power and energy is still fuzzy, the kW vs kWh explainer walks through it. To go the other way, from kWh back to watts, you rearrange the same formula, which is further down.
Why can't you convert watts to kWh directly?
Because watts are a rate and kWh are a total, and you cannot turn a rate into a total without a length of time. Watts measure power, the speed at which a device uses energy right now. Kilowatt-hours measure energy, the amount piled up over a period. It is the same relationship as speed and distance: miles per hour is a rate, miles is a total, and you need hours to get from one to the other. A car at 60 mph has not traveled any distance until time passes; a 60 watt bulb has not used any energy until it runs.
This is why a question like 'how many kWh is 400 watts' has no single answer. 400 watts is 0.4 kWh for every hour it runs, so it is 0.4 kWh after one hour, 0.8 kWh after two, and 4 kWh after ten. The wattage sets the rate; the hours set the total. Any watts-to-kWh answer you see that skips the time is quietly assuming one hour of runtime without saying so.
How many watts is 1 kWh?
One kWh is 1,000 watts running for one hour, which is 1,000 watt-hours of energy. But it is any pairing of watts and hours that multiplies to 1,000 watt-hours: 1,000 watts for 1 hour, 500 watts for 2 hours, 100 watts for 10 hours, or 250 watts for 4 hours all equal exactly 1 kWh. So no fixed wattage 'is' a kWh; a kWh is a bucket of energy that many different rates can fill in more or less time.
That settles the common 'is 1,000 watts one kWh' question: only if it runs for exactly one hour. A 1,000 watt microwave on for six minutes uses just 0.1 kWh, and the same microwave on for two hours would use 2 kWh. The watt rating by itself never equals a kWh; the hour does. Going backward, to find the watts behind a known kWh figure, use watts = (kWh times 1,000) divided by hours, so 1 kWh spread over 4 hours is a 250 watt draw.
What is 2,000 watts in kWh?
2,000 watts is 2 kWh for every hour it runs (2,000 divided by 1,000). To turn any wattage into kWh per hour, just divide the watts by 1,000: 100 W is 0.1 kWh per hour, 500 W is 0.5, 1,000 W is 1, 1,500 W is 1.5, 2,000 W is 2, and 3,000 W is 3. Then multiply by however many hours the device actually runs. A 2,000 watt appliance used for 3 hours is 2 times 3, or 6 kWh.
Once you have kWh you can price it. Multiply the kWh by your electricity rate, which is on your bill in dollars per kWh. The US residential average is roughly 17 cents per kWh as of 2025, though rates run from about 11 cents to over 40 cents depending on the state, so use your own. At 17 cents, that 6 kWh costs about $1.02 to run. This is how appliance running costs get worked out; our guides on how many watts a refrigerator uses and how many watts a TV uses put real wattages and daily kWh to two of the big ones.
How do you convert watts to kilowatts and watt-hours to kWh?
Those two are direct, no time needed, because you are only changing the unit of the same quantity. 1 kilowatt is 1,000 watts, so watts to kilowatts is divide by 1,000 (1,500 W is 1.5 kW) and kilowatts to watts is multiply by 1,000 (3 kW is 3,000 W). Likewise 1 kWh is 1,000 watt-hours, so watt-hours to kWh is divide by 1,000, and kWh to watt-hours is multiply by 1,000. These look like the time-based conversions, which is the only reason they trip people up.
The one to keep separate is watts versus watt-hours. Watts to kilowatts is just a unit swap; watts to watt-hours needs the hours (Wh = watts times hours). A 100 watt panel is 0.1 kilowatt no matter what, but whether it makes 100 watt-hours or 800 watt-hours depends on how long it runs. Battery capacity is quoted in watt-hours or amp-hours for this reason; if you are converting a power bank's rating, mAh to kWh covers that path, and what a 100Ah battery can run turns amp-hours into real runtime.
How does watts to kWh apply to solar?
For solar you work in kWh, because that is what panels produce over a day and what your bill counts. A panel's wattage is its rate in full sun; its daily energy is that wattage times the hours of strong sun it gets, divided by 1,000. That is why a 400 watt panel is not a fixed kWh figure: its output depends on your location's sun hours, which is exactly the confusion behind 'how many kWh is 400W.' The 400 watt solar panel guide gives real daily output ranges, and to match an array to your own use, run the numbers through the solar panel calculator rather than guessing a sun-hour figure.
This matters because your utility bills you in kWh, not watts, so sizing solar means matching kWh produced against kWh used, both measured over the same period. Add up a month of kWh from your bill, and an array is sized to cover some or all of that monthly energy. Watts describe the hardware; kilowatt-hours describe the job. Keep the two straight and the rest of the solar math (bill offset, battery storage, payback) lines up on one unit.
Frequently asked questions
How many watts makes 1 kWh?
1,000 watts running for one hour makes 1 kWh, which is 1,000 watt-hours of energy. It is also any watts-and-hours pair that multiplies to 1,000 watt-hours, so 500 watts for 2 hours or 250 watts for 4 hours each equal 1 kWh. No single wattage is a kWh on its own; the running time completes it.
Is 1,000W the same as 1 kWh?
Only if the 1,000 watt device runs for exactly one hour. 1,000 watts is a rate of power; 1 kWh is an amount of energy. Run 1,000 watts for one hour and you get 1 kWh; run it for 30 minutes and you get 0.5 kWh; run it for two hours and you get 2 kWh. Watts times hours, divided by 1,000, gives the kWh.
What is 2,000 watts in kWh?
2,000 watts uses 2 kWh for every hour it runs (2,000 divided by 1,000). For a total, multiply by the hours: 2,000 watts for 30 minutes is 1 kWh, for 3 hours is 6 kWh. At a US average near 17 cents per kWh, each hour of 2,000 watts costs about 34 cents, but use the rate on your own bill.
How many kWh is 400 watts?
400 watts is 0.4 kWh for each hour it runs, so 0.8 kWh over two hours and 4 kWh over ten. As a 400 watt solar panel, the daily kWh depends on how many hours of strong sun it gets, not a fixed number; the 400 watt solar panel guide has real output ranges.
How many watts are in a kilowatt?
Exactly 1,000 watts are in a kilowatt, and 1,000 watt-hours are in a kilowatt-hour. That conversion is direct and needs no time. What does need time is watts to kWh, because watts measure power and kilowatt-hours measure energy, which is power multiplied by hours.