Solar energy has made some inroads into the housing market, but the sight of a house with roof-top solar collectors is still something of a rarity. s

One reason for the dearth of solar homes is that many builders are wary of the problems of building and selling sun-powered houses, and many prospective home buyers are equally wary of purchasing such homes.

The Department of Housing and Urban Development, which has helped push the development of residential solar energy through its grant programs for about four years, is attempting to cast some light on the solar-related problems of builders and buyers.

A recent 28-page report commissioned by HUD, "Selling the Solar Home '80," reached generally optimistic conclusions on the matter.

But while the solar outlook is encouraging, the report said, more facts are needed. Based on responses to a survey of participants in HUD's demonstration-grant programs, the report said that home buyers are definitely interested in solar energy, but they are even more interested in saving money.

"Continuing research is needed to clarify the extent and depth of the solar residential market," it noted. "More must be learned of consumer willingness to pay the front-end costs of solar energy systems. And repair and service experiences will have to be traced to determine frequency and cost of repairs."

The size of the actual monthly bills for heating is a key element, however: "To most homeowners . . . . utility bill savings are critical. For solar to capture a meaningful market share, it will be necessary to have hard data to document energy savings and relate these savings to operating expenses and the initial cost system.

Most of the findings are based on reports from about 60 homes equipped with "active" solar-energy systems -- those that use large collectors, usually located on a roof, and have pumps and other mechanical equipment to deliver the collected heat to the point of use. HUD conceded that passive solar designs, which utilize nonmechanical systems such as large south-facing windows, "are gaining momentum among professional builders." l

The report also concludes that the ultimate test of solar energy's acceptance by home buyers is the daily experiences of those who are living with solar-powered equipment.

The experiences, the survey found, brought mixed reactions. About four of every 10 owners of solar homes are not satisfied with the solar-energy system, even though most are satisfied with the home itself.

The principal reasons for the dissatisfaction are: The solar equipment saved less money than the homeowner had expected, temperature control was more difficult than expected, and the frequency of repair and service problems was too high.

More than half the solar-home purchasers said a reduction in utility bills was the main lure to buying the home, and about half said use of the equipment convinced them that there actually was some saving. Most of the remaining half said they either had not saved on utility bills or couldn't determine the extent of the saving.

About half the solar homeowners said they found maintenance procedures for the system more frequent and more complex than they had experienced with conventional heating systems.

One step toward solving the dissatisfaction problem, the report says, is for builders and solar-equipment manufacturers to avoid inflated performance claims. "Builders need to be aware that solar effectiveness and the cost savings of solar systems are very difficult to measure in the real world," the report warns. "Homeowners are not tolerant of exaggerated cost-savings promises that are not fulfilled." More than one-fourth of the solar purchasers -- 28 percent -- also feel that reliable solar service is not yet available in their areas.