Editor's note: Third in a a four-day Deseret Morning News series examining Utah's energy future.

The most environmentally sensitive and economical ways to reduce power consumption and improve air quality undoubtedly involve conservation and better efficiency.

But few experts maintain these tools by themselves will fill the gap between demand and generating capacity, or between global warming and clean air.

Among often cited alternatives to conventional power stations like coal and nuclear-fired plants are those running on the nonpolluting, renewable sources of solar, geothermal and wind power. All have advantages and drawbacks.

PacifiCorp, which does business in Utah as Rocky Mountain Power, has generating capacity of more than 9,000 megawatts. (As Rocky Mountain Power, it services Utah, Wyoming and Idaho. As Pacific Power, it operates in Oregon, Washington and California. The utility supplies most of Utah's electricity needs.)

Utah's demand for power during peak periods has risen from about 3,000 megawatts in 1996 to more than 4,000 megawatts in 2007, according to Rocky Mountain Power. (Without going into the complexities involving the amount of time turbines are operating, one megawatt supplies enough electricity for about 500 homes.) What it cannot produce, it must buy from other utilities.

As growth continues, purchased electricity can be expected to become scarcer and more expensive.

PacifiCorp estimates that unless new sources are used, it will have a power generating deficit in its six states of 750 megawatts by 2010. Should that trend continue, the deficit will pass 1,000 megawatts the next year, surge to nearly 2,500 megawatts by 2012, and reach 3,000 megawatts in 2016.

The need to step up power generation is obvious, assuming Americans aren't willing to suffer electrical blackouts or to deliberately set back the economy.

PacifiCorp has ruled out nuclear plants and additional coal-fired units in Utah for the time being, said Dave Eskelsen, spokesman for Rocky Mountain Power in Salt Lake City.

"In our current planning cycle, the need that we have for new resources is soon," he said. "A nuclear project, even if it were started today, would not be on line by the time we need it, which is 2012 and the years beyond that."

Conventional wisdom is that even if the approval process were expedited, it would take 15 years to complete the permitting process and build a nuclear power plant, according to Eskelsen.