Last updated on October 24th, 2019
Do you know the difference between kW and kWh? In this kW vs. kWh article, we will help you determine the difference.
kW vs. kWh: How to Determine the Difference (And What They Mean)
While most people would not tell the difference between kW and kWh, it is essential that we try to make them do. Kw vs. kWh is a concept that even some energy professionals don’t fully understand.
However, if you want to know the amount of electricity that you need in your home or business, it becomes critical for you to identify the difference.
If you are one of those people who regularly use the words interchangeably without knowing which one is which, then this article will be ideal for you.
Also, if you can put a distinction between kWh vs. kW will help you to understand your energy bills better. You can even understand how different appliances or machines in your home or business consume energy.
To better comprehend the two terms, we will first try to explain each word independently and then compare them. This article will offer the detailed meaning of these terms in the simplest forms to help you relate better.
Simple definitions: Kw vs. kWh
A simple definition of kilowatt (kW) would be to say; it is the measure of power. On the other hand, a simple definition of kWh (kilowatt-hour) is the measure of energy.
The initials stand for;
K – kilo (1000)
W – Watts
H – hours
Although it may seem simple, many people even after seeing these terms for the longest time, still can’t figure out the difference. Also, the terms energy and power may tend to complicate things even further.
Just like kW vs. kWh, energy and power are words that people always use when they meant to mean the other.
For this reason, it is crucial that we understand the difference between the two so that we can easily understand kW and kWh.
What is Power?
Power can be defined as the rate at which energy is used or generated at any given time. When we talk of how much power an appliance or an electronic need to operate at any given time, we speak of kilowatts (kW). It is the electricity load.
Just like a moving car where speed can be defined as the rate at which distance is covered, the same way power is the rate at which energy is consumed or generated.
As kW is the measure of power, the higher the kW a building needs to operate, the higher the rate at which it is consuming energy. There are 1000 watts per kW and therefore, to determine the kW of an item that is rated in watts, you divide by 1000.
When it comes to solar panels, the size of the panel will be defined using its peak power. The peak power is the amount of power the solar panel produces at maximum sunlight.
For example, a 2-kW solar panel will produce 2 kW of power on a hot day.
See Related: Best Solar Panels to Buy For Home
What is Energy?
Energy refers to a measure of how much fuel something contains, or uses over a definite period. Therefore, when we say that kWh is a measure of energy, we mean that it is the total amount of energy that you can use over a stated period, let’s say an hour.
For example, if you have a machine that requires 1000 watts to operate, and you run it continuously for one whole hour, it means that you spend 1000 watts or 1kWh of energy. It is merely the number of kW that an item will require to function for a given period.
The total measure of electricity you can use (or generate) is what we define as kWh. Some, for example, can say, “My solar system generated 3 kWh of energy today!”
In other words, if you have a light bulb rated at 100 watts, it will take the bulb 10 hours to exhaust 1kWh of energy. A 50-watt light bulb will stay on for 20 hours for it to consume 1 kWh, while a 2 kW item will take half an hour to exhaust the 1 kWh of energy. Like these stats? Consider reading about these facts about electricity.
You can use our potential energy calculator to determine the energy of an object.
See Related: What is Net Metering and How Does It Work
How to Determine the Difference between kW and kWh
Using the above definitions, we can now look at a comprehensive example to help us get the concept even better. For our case, we will take two models of cars, traveling at different speeds, but for the same period.
|Car model||Distance in miles||Time in hours||Speed (mph)|
Since kW is the measure of the energy that something needs to operate, it is sometimes referred to as the “demand” while kWh as the “consumption” or “usage” as it’s the energy spent over a while.
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Back to our example:
While the two cars travel for the same period, we can see a big difference in terms of the distance covered by each vehicle. The Ford Escape covers a range of 500 miles after five hours since it was traveling at a speed of 100 mph. In other words, it required or demanded speed of 100 mph to be able to cover the 500 miles.
If we compare this to the demand of energy in a home or a building, we can equate speed (mph) to the kilowatt (kW), as both stands for the demand at any given time. Therefore, just as we require a rate of 100mph at any given time for the Ford, we would need 100 kW to operate the building at any given time.
On the other hand, if we equate the total distance covered to the overall “consumption” of energy at a building, then the equation will be; Distance Travelled (mi) = The Kilowatt-hour (kWh).
If we take the Ferrari for instance, it covered a distance of 850 miles in 5 hours. This means that for the specified, which is 5 hours, the car covered 500 miles.
Equating this to the consumption of a building, we would say that our energy consumption is 500 kWh for the 5hrs. So, kWh does not mean the amount of kW consumed per hour, but rather the amount of energy something consumes over a determined period.
Since we can see that the two cars cover two different distances while operating at the same number of hours, it is also possible for two buildings to run for the same amount of time but consume different kWh.
Relationship Between energy (kWh) and power (kW)
Using the explanations above, we can see that kWh is kW multiply by time. Therefore, the equation becomes; kWh = kW * h,or energy = power * time. This shows that the two are interrelated and in the world of electricity, both are important.
For instance, 1 kWh is equal to one-hour usage of electricity at a rate of 1 kW.
It is also okay to say that 2-kW appliance will use 2 kWh in one hour.
Another essential term we need to understand, especially for those using renewable energy as a source of electricity is the capacity ratio. Many people have installed solar systems or wind turbines but still can’t tell the difference between the actual power generated, and the installed capacity.
While determining the installed capacity is easy, calculating the actual output is the challenge.
In simple terms, the capacity ratio of a system is the actual power produced over a certain period, divided by the total installed capacity (max possible power output).
To calculate the installed capacity, you add up the rated capacity of all your solar panels.
See Related: A Complete Guide to Prepaid Electricity
Here is an example
Let’s say, if you have four solar panels rated at 2Kw each, then the installed capacity will be 2 kW multiply by four, which equals to 8 kW. Just as the actual power output varies in various locations, the capacity factor for a solar system will also vary based on site.
The difference is caused by the different solar scores found in different places.
To illustrate this scenario, we can take two different cities like Phoenix, which has a solar score of 84 and Seattle, whose solar score is 43.
If for example, we consider a solar system with a 10 kW peak capacity and install it in both cities, their capacity factor will be as follows.
If the average solar power produced in a year is 20,500 kWh, and the installed capacity at that peak capacity is 87,600 (24 x 365 x 10), then the capacity ratio is 20,500/ 87,600 *100 = 23%.
In Seattle, whose Solar Score is 43, the same 10kW system will produce 14,000 kW. Dividing this by 87,600 you get 16%.
Generally, the ratio ranges between 10-25% depending on the availability of the sun or wind in the case of the wind system.
See Related: How to Calculate Electricity Usage Charges
How Much is 100 kW
Being able to differentiate between kW and kWh is a big step in managing your power bills. Also, it is beneficial to know how these units of measures can be converted. Most manufacturers rate various appliances in either kW or watts, it is crucial to understand how to convert one to the other.
For example, if you are asked how much is 100 kW, I think the right question should be, how many kWh does a 100-kW system produce?
To clarify, the reason the question changes is because as we know, kW is the measure of power while kWh is the measure of total energy generated over a specific time.
Therefore, to answer the question, a 100-kW solar system means that the system can produce 100 kW of power at any given time with the maximum sunlight.
If for instance, the system receives maximum sunlight for a period of let’s say 4 hours, it means the panels can produce a total of 400 kWh of energy. i.e. 100 kW * 4 hours = 400 kWh.
Based on that example, we can, therefore, conclude that the amount of energy produced by a solar system, will depend on the total peak hour (kW) multiplied by the hours of sunlight.
Importance of kW vs. kWh
Although many people may assume it and view it as just scientific differences, it can significantly help you understand your power bills more. It will enable you to know how much energy you consume, what appliance consumes what power, and at what rate.
When shopping for a solar system to install, this knowledge will help you choose the right size for your needs.
For example, the average Connecticut power rate for a commercial customer is 12.22 cents/kWh or $15.45/Kw at peak hours.
Therefore, a 2-kW item that consumes 100 hours per month will incur $24.44 in consumption charges.
See Related: Fronius Smart Meter Review
Conclusion on kW vs. kWh
Having a clear distinction on Kw vs. kWh is essential to help realize the amount and rate at which they consume energy. I hope this article provides you with everything you need to know about the differences between kW and kWh.
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