What is a Kilowatt-Hour (kWh)?
- The kilowatt-hour is what electricity providers use to measure electricity usage.
- 1 kilowatt-hour = 1,000 watts sustained for an hour.
- A watt-hour indicates the amount of energy used.
- A watt indicates the rate of energy use.
What is a Kilowatt-Hour (kWh)?
The kilowatt-hour (abbreviated as kWh) is the basic unit of measurement that your electricity supplier uses to measure your electricity usage. If you live in an energy deregulated state and compare electricity prices, all of the prices are based on kilowatt-hours.
In technical terms, the definition of a kilowatt-hour is 1,000 watts sustained for an hour.
But this can still be a little abstract for some, so if you want to understand what causes that increase your electricity meter, you need to know the difference between a watt and a watt-hour.
A Quick Lesson In The Metric System
Pretty much everything mentioned in this resource is based on the metric system. In the US, we use the imperial system (i.e. inches, miles, gallons, etc.), so we don’t get much experience with the metric system.
Everything in the metric system starts out with a base unit. On this page, our base unit will be a watt or a watt-hour. (But other common base units are meters, liters, grams, and bytes.)
Whenever “kilo” is placed in front of one of these base units, that means it multiplies it by 1,000. For example, 1 kilowatt = 1,000 watts. Same thing with kilowatt-hours. 1 kilowatt-hour = 1,000 watt-hours.
This can move into smaller units as well. For example, 1 milliwatt = .001 watt.
If you are interested in how other metric conversions work, here is a table:
What’s the Difference Between a Watt and a Watt-Hour?
A watt is a unit of power.
A watt-hour is a unit of energy.
They sound similar, but there is a difference.
A watt tells us the rate at which energy is either used or produced. For example, a 700-watt microwave needs electricity at a rate of 700 watts to operate. It is similar to miles-per-hour with a car.
A watt-hour is the amount of energy used. It tells you how much energy that 700-watt microwave used, depending on how long it was on. If we stick with the car analogy, it is similar to the distance measured.
Here are a few examples.
How To Calculate Watt Hours
If you have a 100-watt light bulb on for one hour, the amount of energy you would have used would be 100 watt-hours.
If you kept that 100-watt light bulb on for 10 hours, you would have consumed 1,000 watt-hours or 1 kilowatt-hour.
Again, think of the car analogy. If you drove 70 miles-per-hour for one hour, you will have covered a distance of 70 miles.
The number of appliances running matters as well. If you had ten 100-watt light bulbs on for one hour, you would have consumed 1,000 watt-hours or 1 kilowatt-hour, the same as if you had one light bulb on for 10 hours.
A Note About Wattage and Appliances
When you are looking at the wattage on an appliance, you may think that a higher wattage means the appliance is more powerful. Even though this is technically correct, you are probably thinking about it in the wrong way.
The wattage of an appliance only tells us the rate of power consumption. It tells us nothing about how efficiently it uses that power.
Think modern-day light bulbs vs traditional incandescent light bulbs. Modern-day light bulbs can put off the same amount of light as a traditional light bulb, at a much lower wattage. That is why lights nowadays are advertised as “60-watt equivalents.” They put off just as much light as a traditional 60-watt bulb but could be using as little as 7 watts.
In other words, just because something has a higher wattage, does not mean that it is a more powerful product. It is often the case, but not always.
How Many Kilowatt-Hours Do You Consume?
Check your electricity bill. Since the kWh is the base unit electricity suppliers charge you by, it will tell you how many kilowatt-hours you used and the cost per kilowatt-hour.
According to the EIA, the average household consumes 914 kWh per month. This will vary depending on the size of your home and how extreme your weather conditions are (are you running the AC or heat all the time?).
If you are trying to find a way to lower the number of kilowatt-hours you use, check out our Energy Saving Guide. This will take you through the biggest energy consumers in your home and help you determine how you can most effectively decrease your energy bills.