So what is a kilowatt-hour anyway?

It’s all well and good to talk about saving energy, but the discussion gets abstract pretty quickly once we start speaking in jargon. If you’ve ever been baffled by energy efficiency economics or stymied by savings shibboleths from temerarious technocrats—in short, if you like things explained in plain English, this post is for you. We’ll assume no prior knowledge on your part, so there will be no need to furtively Google “what is a [technical term]” in private browsing mode.

Let’s start with watts, the basic unit of power. In physics terms, power is the amount of energy used in a given amount of time. For instance, if you want to carry a heavy box up a set of stairs, but are feeling a bit lazy, you might take it up a few steps, stop for a rest, go up a few more steps, get a drink (it’s important to stay hydrated when you’re working!), then finally bring it up the last few steps. However, if you’re feeling particularly motivated and sprint upstairs, the box travels the same distance in less time, and more power is required.

In the world of electronics, motors, and the like, power is an important consideration. Light bulbs provide us with a shining example, as they come in a variety of “watt flavors”—60 watts, 100 watts, and so on. (Incidentally, “watt flavors” is a made-up term. If you use it in conversation with an engineer, they will laugh at you.) However, that number by itself doesn’t give us any information about the amount of energy we use. If I leave my 40-watt desk lamp running day and night, it will clearly use more energy than a 400,000-watt experimental laser that I haven’t turned on…yet. Also, since large numbers can be unwieldy, we would probably refer to that secret experimental laser in my garage as a 400-kilowatt device—1 kilowatt is equal to 1000 watts.

This is where the “hour” part of “kilowatt-hour” comes in. If we’re going run our lights, lasers, and so on, we’re going to need to measure the time we run them for—at least, if we want to know how much energy we’re using. Therefore, we use an hour as the generic base amount of time. This allows us to compare the amount of energy different appliances use (even if they don’t generally stay running for an hour, we can at least say how much energy something would use if it ran for an hour).

You can check out this list of a few common household items and their approximate energy usages for some real world examples.

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