As you study your electric bill, you might be wondering what are kilowatt hours? In this post, we are going to talk about kilowatt hours (kWh): What they are, how to calculate them, and why you would want to know. Let’s dive right in with our first question.

Wikipedia says it is a unit of energy equal to 3.6 megajoules. That doesn’t mean anything to me, how about you? What about this: A kilowatt-hour is equivalent to one kilowatt of power sustained for an hour. That is a little bit better, but how much is a kilowatt? Well, one example from Wikipedia is that a 100 watt television that runs constantly for 10 hours will use 1 kilowatt hour. To produce one kilowatt hour in terms of manpower, a healthy adult male can perform about half a kilowatt hour of power in an 8 hour day. That puts it into perspective for us, doesn’t it? The power used by your appliances is measured in watts. So, a watt is a measurement of power, and a kilowatt-hour is a measure of power over a period of time.

Now that we know what kilowatt hours are, let’s figure out your kilowatt hours for an appliance, you want to take the watts it uses, divide by 1000 and then multiply by the number of hours. We’ll use an LG 55″ 4K Ulta HD Smart LED television as an example. It is rated at 120 watts.

120 / 1000 = 0.12 kilowatts per hour.

0.12 * 4 hours per day = 0.48 kWh per day

0.48 kWh per day * 30 days per month = 14.4 kWh per month.

That’s not so terrible, is it? Oh, but wait, you bought a really nice receiver and stereo to go with that television. Mine runs about 400 watts to power the speakers and it’s nothing exceptional. So, the stereo is using:

400 / 1000 = 0.40 * the same 4 hours per day = 1.60 * 30 days per month = 48 kWh per month.

Okay, so my television and stereo together are costing me 62.40 kWh per month (14.4 for the TV + 48 for the stereo). At current baseline rates for Edison, that’s about 17.5 cents per kWh or $10.92 for the month. Just to watch a little TV at the end of the day!

Here is a quick calculator to help out.

Now that you know your wind-down time at the end of the day is running close to $11 a month you might be thinking you would rather not know about any of this. It’s kind of frustrating when you think about how easy it is to add a few bucks to the electric bill. The good news is that now you’ll be able to put a real figure to those Energy Star labels and make better choices on your next big purchase. But what about the day to day stuff? Have you checked your light bulbs? If you are still running regular lights, you should consider investing in the mini Energy Saver bulbs. They will save you money over the long run.

I bought a Costco pack of 13w probably ten years ago. Those bulbs traveled with me over the course of two moves and more than half of them still work fine. I don’t run a lot of lights because I, too, am trying to keep my electric bill down. Something along these lines should drop the light portion of your electric bill pretty quickly. Remember that 60 watt bulb you’re running while you enjoy your 4 hours of television is costing about $1.26. PER BULB per month (7.2 kWh). If you’re running more than a single bulb, then your cost will increase significantly. When you switch to the mini Energy Saver bulbs, they only cost $0.27 per month on the baseline tier. That means you can run 3 bulbs for $0.82 instead of $3.78 per month! Use this through your home and you will see an improvement in your electric usage.

Let’s not forget about the tiered rates, though. Most locations have between 200 and 400 units of electricity available in the baseline, or least expensive, tier. If you, like most of the people I know, are in the second or even third tier, then your wind down time will cost more as the month goes on. The usage for your wind down time in the evening counts for almost a quarter of your baseline rates in the winter. We get further into that in another article. For now, just remember, the baseline is the least expensive tier, varies by area, and has a higher allocation in the summer.

To recap, kilowatt hours are a measure of your appliance’s electric usage over the period of time it is being used. That figure can be used to calculate your monthly usage on most items in your home so you know where your electricity is going. And we figured out that our evening television time uses about a quarter of our baseline usage in the winter. I hope this helped! Please comment any questions you have below and we’ll answer them for you!

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