When top presidential aides get up from lunch at the White House staff dining room, their dishes are whisked away to be washed in water that is heated by sunshine striking solar panels on the roof.

The White House system is one of about 250 or more solar installations -- private, commercial and governmental -- that have sprung up in the Washington area in the last few years as residents look to the sun for help in combating risin energy costs.

Because of costly security measures, the White House solar system is not an impressive money saver: It cost $28,000 and saves only $1,000 a year in energy costs.

But other solar systems, especially in homes, can reduce bills dramatically, the experts say. They expect the infant solar industry to be booming soon.

Acceptance of solar energy devices is developing slowly but steadily, with the biggest questions centering on costliness and reliability. A space heating system, for example, can cost $10,000 and may not pay for itself in a reasonable period of time. And solar systems in many cases are most effective only when used as backups for traditional heating systems.

Nationally, the pattern is similar. More than 5,000 new homes across the country have incorporated solar principles into their design, and about 150,000 solar energy systems of all kinds have been put into operation.

Next year, the U.S. Department of Energy will spend $84 million to promote solar energy uses.

There is no consensus on solar energy.

"Solar is taking off, there are exciting things happening in the marketplace," said Frederick H. Morse, director of the office of solar applicatons for Energy Department buildings.

For example, Morse said, sales of rooftop solar-collecting panels nationwide increased 20 percent last year.

But Daniel Erginn, coeditor of the Harvard Business School's widely read study, "Energy Future," said, "We're still very much at the beginning in solar. There's a lot of learning that needs to be done."

President Carter has said that the nation should get 20 percent of its energy by the year 2000 from solar and other renewable energy sources such as wood, wind and water. Yergin's book says that goal is feasible but quotes the dissenting view of one trade publication editor that solar in the next 25 years will have the impact of "a mosquito bite on an elephant's fanny."

Most solar hot water systems for houses cost about $2,500 and now appear to be economical in the Washington area, paying for themselves in energy savings in about five years.

Space heating systems can cost four times as much but the big initial investment can cut heating bills sharply -- a Washington Post survey of a dozen solar installations in the area found one solar heating system that provides 60 percent of a building's heat.

Among the more esoteric solar applications in the area are photovoltaic wafers that directly transform sunshine into electricity. These are being used in suburban Virginia to feed a small current into the steel structure of a bridge, a procedure that prevents corrosion.

Solar window film is being used in a big office building at Tysons Corner to keep the sun's rays out in the heat of summer, substantially cutting the building's air-conditioning costs.

This area is also the site of many government-subsidized projects -- such as the White House system -- designed to demonstrate that solar energy systems work.

Among homeowners, solar hot-water systems are the most popular. Such systems can work all year round in this area -- except on cloudy days -- and can be expected to supply half or more of the hot water needs of a family of four. Such a family typically spends several hundred dollars a year for hot water.

Local solar experts say that a new 40 percent federal income tax credit on solar installations is providing a big boost.

The credit allows homeowners to deduct from their federal income tax bill 40 percent of what they spend on most solar systems. For example, an expenditure of $2,500 for a solar hot water system would qualify for a $1,000 credit -- that is, $1,000 knocked off the sum that a taxpayer finds he owes after computing everything else on his tax return.

Joni King of Futuristic Solar Systems Corp., a suburban Maryland manufacturer and installer of solar equipment, said the firm has sold 30 expensive solar space heating systems this year -- a surprise because only five were sold last year. King said the tax credit may be the reason.

Companies such as Futuristic, along with solar advocates in government and in private think tanks, say that systems such as these have short payback periods -- the number of years it takes for a solar system to pay for itself in energy savings and then start providing free energy from the sun.

"If it's more than a three-year payback [on a hot water system], it's a rip-off," said Futuristic's King.

But The Washington Post's check of installations in the area indicated such short payback periods could not be routinely expected.

Elenor Whittle of Anacostia had a solar hot water system installed in her semidetached brick house free of charge by a local organization, the Anacostia Energy Alliance, in July last year.

Since then she has saved about $100 on her natural gas bill and has had no problems with the system. In fact, Whittle said, she is delighted with it.

But if she had had to pay for it herself, she said she couldn't have afforded it.

Natural gas is less expensive than electricity. A Washington Gas Light Co. study during the past year of two homes with solar hot water indicated that it would take about 30 years for the solar systems to pay for themselves if they were replacing natural gas systems.

However, Chevy Chase architect Mark Velsey installed a solar hot water system in his house and said it has cut his gas bill drastically.

"My gas bill last month was $8," he said. My neighbor next door [who uses gas for his stove and hot water as Velsey previously did] spent $25 for gas last month."

Solar hot water systems are known as "active" solar systems because they involve fluids that move and, sometimes, moving parts.

They work like this:

An antifreeze-like fluid moves through black boxes on the roof or outside walls of a building. The door-size boxes are tilted toward the south so the sun's rays directly strike though their glass or plastic faces, heating the fluid.

The heated fluid circulates to a heat exchanger in a water heater, heating the water in it for use in the house. These water heaters must be extra large -- sometimes holding more than 100 gallons -- because the recovery time for such a system is slow.

Usually the system will be linked to a backup gas or electric system, and a small electronic sun sensor may be used to tell the system to switch over on a cloudy day. Various mechanical or electronic devices may be used to drain the system in particularly cold weather so it won't freeze up and burst its pipes.

Solar space heating systems are generally simply larger versions of this, circulating the hot water through the house to heat it.

The space heat systems are also linked in with backup systems for use in long periods of cloudy or extra-cold weather. Futuristic, for example, uses a wood-stove system as a backup.

David Wolcott of Mount Pleasant spent $300 a few years ago creating a "sunspace" on the south-facing back porch of his second-floor apartment, saving so much in heating bills that his landlord hasn't raised his rent in years.

Wolcott simply installed plastic material, enclosing and sealing the porch. He painted the rear brick wall inside the porch dark green so sunlight would come through the plastic mateial and strike the wall, creating heat that is held in the "thermal mass" of the wall. The double sheets of plastic keep the heat from going outside again.

During the night the wall releases its heat, keeping Wolcott's apartment warm. He also insulated the apartment carefully to help retain the heat, and installed an outside overhang above the plastic so that in the summer, when the sun is high, it does not come in and overheat the apartment. In the winter, when the sun is low and in the south, its rays come in strongly and directly.

The Anacostia Energy Alliance, a private organization funded by the federal and District of Columbia governments, spent $3,000 installing a "Trombe wall" -- so named for a Frenchman who invented it -- on the south side of its building on Martin Luther King Jr. Avenue SE.

The installation, which provides 60 percent of the heat for the Alliance's small office building during the winter, consists of 512 square feet of plastic covering the brick south wall with a space of several inches between the plastic and the dark-painted wall.

Ducts are cut through the wall into the office space and the air flows automatically as hot air from outside comes inside through high ducts and cooler air from inside goes outside through lower ducts to be warmed.

David R. Cawley, director of the Alliance, figures his Trombe wall will pay for itself in seven years.

A solar greenhouse arrangement at the St. John's Child Development Center on MacArthur Boulevard provided so much heat last winter to a carpentry shop to which it is attached that the shop got too warm.

"A lot of people are working to dispel the image of elaborate technology that only pays off over a long period of time and is a toy for the wealthy or upper middle class," says Mary E. Morrison, a member of the board of the D.C. Solar Coalition, a private group. "Passive solar is low-cost. You can do a lot of the work yourself if you can do basic carpentry."

New buildings may be designed and positioned on their sites for maximum passive solar heat gain in winter and minimal heat gain in summer at an added design and construction cost of only 1 to 3 percent, according to John Holton, director of the energy conservation division of the U.S. General Services Administration.

The GSA is designing all its new buildings nationwide this way, Holton said, and the results are spectacular -- the agency is well on its way toward the federal goal of using 45 percent less energy in its buildings in 1985 than used in 1975.

The agency also has some active systems, but only on an experimental, subsidized basis because of the costs.

Holton said that solar energy installations must be carefully tailored to particular parts of the country and for particular uses. Solar space heating is less cost effective in the South, for example, where there is a very short heating season. But solar domestic hot water heating is more cost effective in the South since hot water is needed year-round.

In New England, where a capital investment in solar heating pays off for many long cold months, replacing the expensive oil heat that is in widespread use there, manufacturers of solar products were severly backlogged last winter, according to the federal Energy Department's Morse.

By the end of 1981, Energy Department officials hope to see 56,000 new homes built on passive solar principles and 300,000 active solar water heating systems installed. There are now 5,000 to 10,000 of the former and about 150,000 active systems of all types in the country, he said.

Surprisingly, one of the most esoteric, high-technology applications of solar energy in the Washington area -- the photovoltaic cluster that is electrifying Dead Run bridge on the George Washington Parkway near McLean -- has been cost-effective.

When Federal Highway Administration officials decided in 1976 to electrify the bridge to prevent corrosion, the Virginia Electric and Power Co. wanted $13,000 to run a power line to the bridge.

But a photovoltaic array that would do the same job was available from the Solarex corporation in Rockville for just $4,000. Solarex, a booming local business, is the world's largest manufacturer of photovoltaic silicone disks that transform sunlight directly into electricity.

Solar film that sticks to windows is increasingly popular and can keep out 80 percent of the sun's rays in the summer and keep in 40 percent of the heat that would escape from a building through the windows in winter, according to Gerald Lowenstein, president Solar Technics Inc. in Bethesda.

Lowenstein has been installing the film in motels and office buildings throughout the Washington area. The dark film has a sticky side that allows it to stick to windows, and its color and the properties of the special material of which it is made allow it to reject the sun's rays. In the daytime, you can see through it to the outside, while from the outside it looks like a mirror and you can't see in.

"It has worked out very well and it keeps the tenants a lot happier," said Leslie Kirk, a real estate specialist with the Prudential Insurance Co. of America and who manages the 12-story Old Dominion Bank Building at Tysons Corner, where Lowenstein recently installed an estimated $30,000 or more in solar window film.

The installation is projected to save about 15 percent on the building's air-conditioning bill, and has stopped scores of complaints that building occupants had about overheating during the summer -- especially on the sides of the building directly exposed to the hot summer sun.

As with most kinds of new technology, solar has its super-enthusiasts. Ralph Rinzler, director of folklife programs at the Smithsonian and owner with his wife Kate of an 1880s flatfront Victorian house on Capital Hill, is one of them. k

Rinzler's house is a virtual solar feast.

His $15,000 system provides solar space heating all winter, working in conjunction with two wood stoves and four fireplaces. It also heats his water all winter and his 800-gallon hot tub for all but the coldest periods of the winter.

Rinzler has a greenhouse off a bathroom and is building another off a bedroom. "The woodstove keeps orchids growing in the greenhouse all winter," he said.

He thinks his investment in solar will be worth the expense.

"It would cost us $300 a month to heat with oil," he said. "I put up $15,000 and got a tax credit . . . . Then you get heat you don't have to pay for, and when I sell the house I've got a fixed investment. Every year it's worth more."