Federal energy officials say solar heating of hot water and construction of homes designed to take advantage of the sun's light and heat will at least double next year.

"Our goal is to have some 300,000 homes with solar hot water heating, which is two to three times what we have now," says Dr. Frederick Morse, head of the Energy Department's office of solar applications for buildings.

In addition, Morse says, homes with passive solar features -- ranging from solar-oriented windows to use of brick and tile to the day and radiate it at night -- are expected to increase to 56,000, more than five times the current number.

The projections indicate the extent to which hot water heating and so-called "passive" design features are the solar energy technologies that currently are the best-developed and most ready for commercial acceptance.

The Energy Department also expects use of solar space heating to multiply several-fold, but even then it's estimated that only 24,000 such systems will have been installed by the end of next year. And photovoltaic cells that convert sunlight to electricity -- an extremely promising solar energy field -- remain largely in the research and development stage.

The department's projections represent the first time it has set goals for increasing the number of buildings using solar energy.

Congress' General Accounting Office charged earlier this year that although President Carter has set a goal of deriving 20 percent of the nation's energy from the sun and renewable resources in the year 2000, there actually was no plan for achieving that goal.

"By the end of next year, we'll be able to see whether we've achieved our goal -- and if not, figure out what the problems are," says Morse.

Federal officials say their projections reflect the fact that solar hot water heating and passive design features are technologies that have come of age.