WASHINGTON, Dec. 6 — Consumption of energy from renewable sources, like the sun, the wind and biological fuels, fell sharply in 2001, the Department of Energy has reported.
The department attributed much of the decline to a drought that cut generation of hydroelectric power by 23 percent. Such variations are natural. But in a report last month, the department's Energy Information Administration also said solar equipment was being retired faster than new equipment was being built.
"Back in the late 70's and early 80's, we had very, very large support programs," said Fred Mayes, who handles data on renewable energy at the energy information agency.
Those programs, begun after the loss of oil from Iran pushed the price to almost $40 a barrel, expired in the 1980's, and "things went into the tank," Mr. Mayes said. Equipment from the boom years is wearing out, and the base of installed equipment is shrinking, he said.
This is true even though shipments of new equipment have risen in the last few years, analysts say. The number of solar collectors, which gather the sun's heat for uses like warming swimming pools, has increased sharply in the last few years, including 34 percent in 2001 alone, the department said.
A spokesman for the solar industry, Scott Sklar, agreed with that assessment. But by the Energy Department's estimate, the total amount of solar energy gathered has fallen three years in a row.
The use of photovoltaic cells, which generate electricity with sunlight, is also growing. Domestic installations were up 80 percent last year, the department reported.
Biomass, including burning of wood or similar renewable products to produce energy and the use of alcohol fuels, declined nearly 2 percent. The use of wind power grew more than 3 percent.
Over all, consumption of renewable energy fell 12 percent to what the department said was the lowest level in more than 12 years, accounting for only 6 percent of the energy consumed in the country.
Of the renewables, biomass accounted for 50.4 percent of the total and hydroelectric for 41.9 percent. The remainder was from the sun, the wind and geothermal sources.
Many environmentalists say solar and wind power have the greatest potential for growth and for displacing fuels that cause pollution and are suspected of causing changes in the world's climate.
The solar total is still very small; 36.3 megawatts of capacity were added in 2001. At that rate it would take 30 years to add the capacity of one large nuclear plant.
For the first time since records have been kept, exports of solar cells declined in 2001. That occurred, Mr. Mayes said, because the companies that build the cells expanded production capacity in other countries.
Solar cells are still too costly to compete with conventional power, but experts say they are increasingly used to supply small amounts of power in places where connecting to the grid would be costly.
Mr. Mayes said he was surprised to find solar cells and batteries being used on the Strip in Las Vegas to provide power to light bus shelters. Although the area has electricity, installing solar cells was cheaper than digging up the sidewalks to put in power lines, he said.