Use our interactive calculator to easily convert watts to kilowatt hours (W to kWh).
kilowatt hours
Conversion formula: kWh = (W × hrs) ÷ 1000
Or would you rather convert kilowatt hours to watts?
Watts to Kilowatt Hours Conversion Chart
Here is a conversion chart converting common values of watts to kilowatt hours, over a duration of one hour and one day.
| Watts (W) | Kilowatt Hours (kWh) @ 1 hour | Kilowatt Hours (kWh) @ 1 day |
|---|---|---|
| 100 W | 0.1 kWh | 2.4 kWh |
| 200 W | 0.2 kWh | 4.8 kWh |
| 300 W | 0.3 kWh | 7.2 kWh |
| 400 W | 0.4 kWh | 9.6 kWh |
| 500 W | 0.5 kWh | 12 kWh |
| 600 W | 0.6 kWh | 14.4 kWh |
| 700 W | 0.7 kWh | 16.8 kWh |
| 800 W | 0.8 kWh | 19.2 kWh |
| 900 W | 0.9 kWh | 21.6 kWh |
| 1000 W | 1 kWh | 24 kWh |
| 1500 W | 1.5 kWh | 36 kWh |
| 2000 W | 2 kWh | 48 kWh |
| 2500 W | 2.5 kWh | 60 kWh |
| 3000 W | 3 kWh | 72 kWh |
| 3500 W | 3.5 kWh | 84 kWh |
| 4000 W | 4 kWh | 96 kWh |
| 4500 W | 4.5 kWh | 108 kWh |
| 5000 W | 5 kWh | 120 kWh |
How to Convert Watts to Kilowatt Hours (W to kWh)
Converting watts to kilowatt hours is easy. First, multiply watts times hours, then divide by 1000.
Formula: kilowatt hours = (watts × hours) ÷ 1000
Abbreviated: kWh = (W × hrs) ÷ 1000
Example
For example, let's say you have a light fixture that uses one 60 W lightbulb, and you leave it on for 4 hours in the evening. Here's how to calculate the light's total energy consumption in kilowatt hours:
(60 W × 4 hrs) ÷ 1000 = 0.24 kWh
So the light's total energy consumption for that evening is 0.24 kilowatt hours. Simple!
Why Convert Watts to Kilowatt Hours?
Any appliance or device that uses electricity will have a watts rating. This rating lets you know the amount of power the device uses at any given moment. When powering your devices with solar energy — whether that's in your home, garage, or camper van — you must know your total energy consumption in order to choose the correct size and number of panels. Kilowatt hours is a measurement of this energy consumption, which is the same thing as power consumed over time.
It is also important to calculate your total energy usage in kilowatt hours when choosing a backup battery. Many solar panel systems also incorporate a battery, for additional energy storage either in the evening or on a cloudy day. Converting watts to kilowatt hours will help you determine how large of a battery to use in your system.
How to Convert Kilowatt Hours to Watts (kWh to W)
You may run into a situation where you know the number of kilowatt hours, and you'd like to figure out watts.
All you need to do to calculate watts from kilowatt hours is to first multiply kilowatt hours times 1000, then divide by number of hours.
Formula: watts = (kilowatt hours ÷ hours) × 1000
Abbreviated: W = (kWh ÷ hrs) × 1000
Example
For example, let's say you've installed a small solar panel system to power the workspace in your garage. You know the average amount of kilowatt hours your system typically produces each day during the summer is 3 kWh. You want to know what appliances or devices you could run inside your workspace during this typical day.
In this example, let's assume that your solar panel system receives 6 hours of full sun during a typical summer's day. Here's how to calculate the total watts available to use:
(3 kWh ÷ 6 hrs) × 1000 = 500 W
So the amount of power available for your workspace during this 6 hour period is 500 watts.
To see what appliances or devices you could power, simply add up the watts rating for each. This rating is usually found on a sticker on the appliance itself, or you can easily look it up via an internet search. As long as the total watts is less than or equal to 500 W, you're good to go!
How to Calculate Kilowatt Hours for an Appliance
Let's look at a real-world example of calculating kilowatt hours for a common household appliance, a room air conditioner.
The next photo shows the electrical specifications for the air conditioner. This is a sticker located on the side of the unit.
In this case, we're given the total watts rating for the air conditioner of 970 watts. We'll assume we want to run this air conditioner for just 4 hours during the afternoon. Here's how to calculate the total kilowatt hours consumed:
(970 W × 4 hrs) ÷ 1000 = 3.88 kWh
Compared to the light fixture we looked at earlier, air conditioners use a lot of electricity!
How to Calculate Kilowatt Hours for a Battery
Next, you may want to know how large of a battery you'll need as backup for your solar panel system. Luckily, calculating how many kilowatt hours you need when choosing a battery is also quite simple.
For example, let's say you are planning on installing solar panels on the roof of your camper van. You also want a battery so you can power your devices in the evenings.
Let's assume you have the following devices, with the following watts ratings:
- a new 15" MacBook Pro, that charges at 87 watts
- mini LED string lights, 40 watts
- overhead lights, 120 watts
- a small fan, 33 watts
- an iPhone, charging at 20 watts
In this example, all of your devices together consume 300 watts. You want to make sure that your battery can provide enough energy to cover even your highest-usage evenings, so let's assume you run everything at once for a maximum of 6 hours.
In this case, the total kilowatt hours you would need is:
(300 W × 6 hrs) ÷ 1000 = 1.8 kWh
However, battery capacities are typically expressed in amp hours, not kilowatt hours. Luckily, converting amp hours to kilowatt hours is also quite simple.
The specifications for any battery will indicate a rating for both volts as well as amp hours. To calculate kilowatt hours, simply multiply the amp hours times voltage, then divide by 1000.
Formula: kilowatt hours = (amp hours × volts) ÷ 1000
Abbreviated: kWh = (Ah × V) ÷ 1000
Calculator: Amp Hours to Kilowatt Hours Calculator
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