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News stories describing the energy generating capacity of renewable projects often try to illustrate the worth of a megawatt in terms of how many homes that a wind or solar project could power. But what exactly is a megawatt, and what is it worth?

First off, a watt is a unit of measurement that measures the rate at which energy is converted into electricity. A kilowatt is 1,000 watts, and a megawatt is 1 million watts. For large energy developments, like Oregon’s wind farms or California’s solar farms, energy is measured in megawatts.

But just because a wind or solar farm has a 100-megawatt generating capacity, doesn’t mean it will produce that much energy. Wind doesn’t always blow, and experts with Horizon Wind Energy say at best, their farms operate at 30 percent efficiency. And even the best photovoltaic panels only operate at 22 percent efficiency because they can’t convert ultraviolet rays, which are instead lost as heat. If you take efficiency into account, a 100 megawatt wind farm becomes a 30 megawatt project and a 100 megawatt solar farm becomes a 22 megawatt project.

Now let’s figure out how many homes can be powered by a single megawatt. According to , the amount of electricity consumed by an individual household depends on the region. An average Oregon household uses about 12,000 kilowatt hours of electricity each year, according to the city of Portland. To convert kilowatt hours to megawatt hours, divide the kilowatts by 1,000. This gives you 12 megawatt hours. If you divide that by the number of hours in a year, about 8,765, you get 0.001 megawatts.

Are you still with me? Finally, if you divide a 30-megawatt generating wind project by 0.001, the number of megawatts an average Oregon household uses in a year, you have a project that can provide power to 30,000 Oregon households each year.

Phew, now wasn’t that simple?