KW VS KWH – Solar Energy Simple Breakdown

In this quick learning guide, let’s break down KW VS KWH in simple English.

You probably have heard these two terms regularly tossed around, but not sure what they mean or which one to pay attention to when it comes to calculating your solar power requirement and cost.

So here is the simple break down:

Are KW and KWH The Same?

KW (Kilowatts) – Energy Demand

KWH (Kilowatt – Hour) – Energy Consumption

Kilowatts measures usage of power at a given time, and Kilowatt Hour measures energy usage over a time period.

More usage = more cost

For Example:

Tom uses about 500 KWH a day, and Dan uses about 40 KWH a day. 500 KWH costs MORE MONEY than just 40 KWH.

How To Really Make Sense Of KW and KWH?

When designing a power system for your RV, home or a large facility, the power size is determined by previous year’s consumption. (generally electric bill will show you all the numbers)

Picture KW as the speed of the car, and KWH is how much power used after a period of time.

For example:

1 KW light bulb running for 1 hour = 1 KWH

1 KW light bulb running for 30 mins (0.5 hour) = 0.5 KWH

5 KW device running for 3 hours = 15 KWH

Sizing Power Requirement

Based on the above explanation, now you should be able to figure out how much power you need.

For example:

Average American household uses up to 890 KWH per month, which means roughly 30 KWH per day.

890 KWH / 30 = 30 KWH per day

Assume 7 peak sun hours per day, which means 30 KWH / 7 = 4.3 KW

Assume you have the option to buy a solar panel rated for 300W per panel.

4.3 KW + 4.3 KW X 0.2 (Account for 20% energy loss in the real world) = 5.16 KW

5.16 KW = 5160 W

How many solar panels do you need for your home in this simple example?

Just take the amount of wattage you need and divided by the rate of energy a single panel can reproduce.

5160 W / 300 W = 17 panels

If you want to learn more about calculating numbers of solar panel required, please read more here

Jeunkong Tai

Recent college graduate from the University of Kansas with an electrical engineering degree and bilingual in Chinese and English. I've learned about solar panels just by being around friends that have them on their home rooftop, and have gained knowledge by helping out on some DIY projects.

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