In his March 18 column, "Drilling the Best Energy Choice," Gene Tye claims that the "power available from a typical Marcellus well (5 million cubic feet per day), in electrical terms, is about 1500 megawatts." From this, he concludes that it would take more than 300 windmills, or 5.8 square miles of solar panels, to produce an equivalent amount of power.

Mr. Tye has confused power (measured in megawatts) with energy (measured in megawatt hours). His figure of 5 million cubic feet of gas produced by a well in a day will indeed run a 1500-megawatt power plant, but only for an hour, not for a day. To keep a 1500-megawatt power plant running full time would require 24 such wells.

In addition, the figure of 5 million cubic feet per day is for a gas well's initial rate of production. Gas production falls off sharply after the first few months: the average production rate over 10 years is more like 0.6 million cubic feet per day. (This is Chesapeake's figure, from the graph on page 6 of the draft report on the economic impacts of gas drilling on Broome County, issued in September, 2009.) So Mr. Tye doesn't need just 24 wells to produce the 5 million cubic feet per day: he needs 8 times 24, or about 200 wells (since it takes about 8 times 0.6 to get 5).

On top of that, Mr. Tye has assumed that 100% of the energy in the 5 million cubic feet of gas will be converted to electricity. But gas-powered plants are typically only about 50% efficient, so in fact it would take about 400 gas wells to produce the electricity he calculates for a single well.

While Mr. Tye is 400 times too generous in his assessment of the power produced by a gas well, it turns out that he is also too generous in his assessment of wind and solar power — but only about 2 to 4 times too generous. Consequently he has vastly overstated the number of windmills or solar panels needed to match the power provided by a gas well.

Here is another way to think about it: if Mr. Tye were correct that a single gas well could run a 1500-megawatt power plant, then it would take only about one-fifth of a gas well to supply all of Broome County's electricity. At this rate, just 300 gas wells could provide all of the electricity used in the entire United States. Mr. Tye should have realized that this is not a remotely plausible result.

Buck