Watts to Kilowatt Hours (W to kWh) Conversion Calculator

What is Watts?

Watts is the unit for power. When applied to electrical systems, it is rate at which an electric circuit uses energy. In other words, it is the amount of energy an electrical system consumes or produces per unit time.

Watts is typically represented with W.

What is Kilowatt Hours?

Kilowatt-hours is a unit typically used for electrical energy. It is the amount of power (in kilowatts) used or produced over a given number of hours. In other words, one kilowatt-hours is equivalent to a power consumption or production of one kilowatt over one hour.

Kilowatt-hours is typically represented with kWh.

Kilowatt-hour (kWh)

A measure of energy consumption or production equal to 1,000 watts used continuously for one hour. This is the standard unit electricity companies use for billing residential customers.

Relationship to Watts

A watt (W) measures instantaneous power, while a kilowatt-hour measures energy over time. To convert watts to kWh, multiply the wattage by hours of use, then divide by 1,000.

Battery Capacity

Home battery systems and portable power stations list their storage in kilowatt-hours, indicating how much energy they can store and deliver. A 10 kWh battery could theoretically power a 1,000-watt appliance for 10 hours.

Solar Production

Solar panel output is measured in kWh to show actual energy generation over time. A typical residential solar array might produce 30-40 kWh per day depending on size and sunlight conditions.

Why Convert Watts to Kilowatt-Hours?

We primarily convert W to kWh to figure out the energy usage of our devices.

Typically, electrical devices come with watts rating, which gives us an idea of their maximum power consumption. But when we want to know the energy consumption of the devices, we must convert the watts rating to kilowatt-hour.

Calculating kilowatt-hours for our devices gives us an idea of how much electricity we are using. With this, we can estimate electricity cost.

Converting watts to kilowatt-hour is also vital when sizing a solar system. For one, it is easier to choose a battery bank with sufficient capacity when you know how many kilowatt-hours all the solar devices will consume.

For instance, if all the solar devices have a total wattage of 0.3 kW, and you intend to run them for 10 hours daily, their total kilowatt-hours (kWh) per day would be 0.3 x 10 = 3 kWh.

Knowing that the daily energy usage of the solar devices is 3 kWh, you’ll know to get a battery bank with a capacity of at least 3 kWh.

Of course, when you have an idea of the capacity of the battery bank you are getting for the solar power system, you can estimate the number of solar panels to get.

How to Convert Watts to Kilowatt Hours (W to kWh)

Converting watts to kWh is simpler than you might think. Once you understand the relationship between power and energy, you’ll be able to calculate exactly how much electricity your appliances consume and what it costs to run them.

The key is knowing that watts measure power (the rate of energy use), while kilowatt hours measure energy (the total amount used over time). A 100-watt light bulb running for 10 hours uses the same energy as a 1,000-watt space heater running for just one hour. Both consume 1 kWh.

The basic w to kwh conversion requires just two pieces of information: the wattage of your device and how long it runs. From there, it’s a straightforward calculation that helps you understand your energy bills, compare appliance efficiency, and make smarter decisions about which devices to use. This matters whether you’re connected to the grid or powering devices like a solar radio with off-grid energy.

Let’s break down the exact formula and walk through some real-world examples that show you how to perform watts to kwh conversions for any appliance in your home.

Watts to kWh Formula

To convert watts to kilowatt-hours, we must convert watts to kilowatts first. Here’s the formula for that:

kilowatts = watts/1000 (1)

Then to finally convert kilowatts to kilowatt-hours, we’ll multiply kilowatts by hours:

kilowatt-hours = kilowatts x hours (2)

Using an electricity bill calculator/watts to kWh calculator would compress these two steps into a single step. To get the formula for that single step, we’ll substitute kilowatts for watts/1000 in (2).

So, instead of converting watts to kilowatts then kilowatts to kilowatt-hours, we’ll have the following:

kilowatt-hours = watts x hours ÷ 1000 (3)

So, we can convert watts to kilowatt-hours by multiplying watts by hours then dividing by 1000. This is what a W to kWh calculator does.

1. Identify the wattage of your device or appliance (usually found on a label or in the manual)
2. Divide the wattage by 1000 to convert it to kilowatts
3. Multiply the kilowatts by the number of hours the device is used
4. The result is your energy consumption in kilowatt-hours (kWh)

Watts to kWh Conversion Examples

Example 1

How much energy will a 2 W solar radio use if it keeps running for 5 hours?

This is a simple one; all we have to do is multiply watts by hours then divide by 1000:

= 2 x 5 ÷ 1000

= 0.01 kWh

Example 2

A ceiling fan rated 220 volts and 1 amp stays on for 8 hours. How much energy (in kilowatt-hour) would it have consumed within the period it stayed on?

This is not as straightforward as the first example because the wattage of the fan was not provided. But since we know the fan’s voltage and amperage, we can calculate watts.

The wattage of the fan:

= 220 x 1 = 220 W

Now, the energy consumption of the fan for 8 hours:

= 220 x 8 ÷ 1000

= 1.76 kWh

Example 3

A 300 W solar refrigerator runs for 8 hours on Tuesday, 6 hours on Wednesday, and 9 hours on Thursday. How much energy did it consume over those 3 days?

This is pretty straightforward. All we have to do is multiply the wattage of the refrigerator by its total running hours for those 3 days. Then we’ll divide by 1000.

Total running hours = 8 + 6 + 9 = 23 hours

Energy consumption in kWh = 300 x 23 ÷ 100

= 6.9 kWh

Watts to Kilowatt Hours Conversion Chart

How Do I Convert My Energy Consumption of Kilowatt-Hours Into Watts?

We can convert energy consumption of kWh to W by adjusting the formula we used for watts to kilowatt-hours (kWh) conversion. But instead of making kilowatt-hour the subject of the formula, we’ll make watts the subject:

kilowatt-hours = watts x hours ÷ 1000

watts = kilowatt-hours x 1000 ÷ hours

Example

What’s the power consumption (in watts) of a ceiling fan if it consumes 1 kWh of energy when it runs for 6 hours?

the power consumed by the fan over 6 hours = 1 x 1000 ÷ 6

= 166.7 watts

Are Kilowatt-Hours Different Than Kilowatts?

Yes, kilowatt-hours and kilowatts are different units. While kilowatt-hours is a unit for measuring electrical energy, kilowatts is for measuring electric power.

How Many Kilowatts Should a Generator Be to Run a House?

The ideal kilowattage of a generator needed to run a house ultimately depends on the total wattage of all the appliances in the building.

For instance, if the total load in your building is 5 kW, you need a generator with a kilowattage greater than 5 kW. Typically, the generator’s kilowattage should by 25% higher than the total load. So, for the 5 kW building, the generator should be at least 6.25 kW.

What Does One Kilowatt-Hour of Electrical Energy Cost?

The cost of one kilowatt-hour of electrical energy varies across the states. But you can expect to pay anywhere between 12 and 35 cents for one kWh of electrical energy in the United States as of 2026.

Knowing how much you pay per kilowatt-hour of electricity in your area can be pretty helpful. For one, you get a sense of how much money you can save when you move some of your load to a solar power system.

Apart from that, if you ever have to cut down your electricity bill by a certain amount, you can readily figure out how many kWh to cut out of your energy usage.