Some mail resulting from a recent Power Play column (see June 11, page 128) suggests there's skepticism-indeed, disdain-out there for the minuscule amount of energy that alternative sources, especially low-efficiency solar, might bring to the table.

If now-daily media coverage of the subject is any indicator, however, I'd say the integrated output of solar, wind and fuel cell sources, among others, will provide significant support for the energy crisis. Just how much is "significant," exactly? I've asked that question for 35 years. Like clockwork, the answer jumps out at me with regularity: 15 percent.

In the last few months alone, we've seen fuel cells and hybrid vehicles presented at technology seminars for the president, several wind farm proposals in the Midwest, solar-powered craft for edge-of-space missions and a race of solar-powered cars across the United States. Hype in the selling? Without doubt. Fuel cells, however, appear serious enough to merit consideration for powering the country's mobile electronics industries, which probably account for well more than 15 percent of business transactions right now.

Funny how alternative technologies are often referred to as "peripheral" solutions, which historically account for about 10 percent of market share. That aside, power-management issues have given us a clue as to "significance," where vendors frequently tout their devices as providing a 10 to 20 percent savings in energy.

So let's say 15 percent, a figure that interestingly (but accidentally) is about equal statistically speaking to the percentage area at the low end of a normal distribution, lying outside the mean-minus-standard-deviation limit.

Pessimists might say this is small potatoes. I say it's akin to determining what percentage of our income we really pay in taxes, and finding out the creeping overhead is more like 45 percent than the 27 or 33 percent our tax bracket might suggest. Not that any actual input or output number is important.

"Now boys, the efficiency of the family slushmobile is about 15 percent," said Dynecourt Mahon, one of my instructors back in the '60s, referring to the typical auto. Maybe a horrible number, but enough to drive an industry.

Whether we're talking 1 percent or 15, the message is clear: Take the payout for an economy that can use all the energy it can get, and be grateful. You're going to need all of it later.