A typical unit would be the kilowatt-hour.
Here is the explanation: A watt is a joule per second. A joule is defined as the unit of
energy required to exert a force of one newton for a distance of one meter. In order to convert a unit of
power into energy, it is necessary to multiply units of power by units of time, that is the time that the power is actually being produced. A 250 MW wind farm, for instance, may produce 250 MW for a fraction of a month, exactly when the wind is just right and at the right speed.
Most people know that if they turn all the lights, toaster ovens, microwaves, electric ovens, etc on for 10 minutes, so that their power demand is ten times as high as normal, and then shut them off and run
nothing for the rest of the month, the electric company will
not bill them ten times as much, even though their
power consumption was instantaneously very high.
This is why electric bills say kilowatt-
hours and not
kilowatts.
I very much doubt that First Energy is buying "watts." It is an energy company. Therefore it is buying energy.
The actual energy involved is, in fact, given in the article. The reporter writes:
Both projects are expected to be operational by December 2007 and will generate 650,000 megawatt-hours of electricity annually.
Now to find the average
power we can simply calculate. First we multiply by 1,000,000 for the "mega" and then we multiply by 3600, the number of seconds in an hour. This gives the
energy output expected for the wind farm in joules. The answer is 2.3 X 10
15 Joules. Now we divide by the number of seconds in a year, 31,557,600, and we find the
average power for the plant, which is 74,000,000 watts or 74 MW.
Dividing by the
peak capacity, given misleadingly as 250 Mega"watts," which is presumably the power generated when the wind is blowing at just the right speed, we see the capacity load of the wind farm. It is 74/250. It is about 30%.
Thus if the plant produces as expected, it will be the equivalent of a 75 watt power plant. This certainly isn't going to drive the coal industry in West Virginia out of business, especially the times of peak demand, hot sunny days needing lots of air conditioning, are precisely the moments that the wind is not blowing. A good breeze
reduces the demand for air conditioning generally.