IF YOU installed a heat pump for your house or solar collectors for your swimming pool, you can forget about claiming either on your federal income-tax form, due April 16. But there are a number of other home energy improvements that are deductible from your 1978 taxes.

Congress had divided these tax incentives into two categories: credits for "energy conservation expenditures", such as insulation and thermal windows, and credits for "renewable energy source expenditures," such as solar, wind or geothermal energy systems.

Conservation measures are eligible for a 15 percent deduction for up to $2,000 spent after April 19, 1977 and before January 1, 1979, on existing residences, such as changing the burner in the furnace. Credit is not given for new homes that use energy-saving devices in this category.

New homes employing "renewable-energy-source" equipment, however, are eligible for tax deductions, as long as occupancy by the taxpayer did not begin until after April 19. These credits are 30 percent of the first $2,000 spent, on solar collectors for heating or hot water, for instance, and 20 percent of the next $8,000. The maximum credit is $2,200.

Several states also have initiated credit programs to spur installation of solar equipment. Among the most liberal of these is California. California grants up to 55 percent credit on state income tax for new solar equipment.

Maryland and Virginia-but not the District of Columbia-have both passed enabling legislation that allows local jurisdictions to exempt solar equipment from property tax assessments. So far, only a handful of local governments have taken advantage of it.

In Virginia about a half dozen passed legislation in response to the new state law. Alexandria is the only jurisdiction in the Washington area to do so, however. Applications to the tax assessor's office are forwarded to Richmond to verify they are legitimate solar applications and conform to state building and plumbing codes.

A similar law passed in Maryland was adopted solely by Harford County. However, a state law applying to all Marylanders prohibits property tax assessments being raised because of the installation of new solar equipment.

The Maryland law, unlike its Virginia cousin, does not require local ordinances fall in line behind state guide-lines. Still, efforts in Prince George's and Montgomery counties, as in Fairfax County, to adopt such legislation have gone virtually nowhere. Some officials fear a loss in property-tax revenues.

There are several conditions governing the federal credits. Installations must be in the taxpayers' "principal residence," which must be located in the United States. Eventually, these devices also will be required to meet performance and quality standards, which do not yet exist. Equipment installed before these standards are issued need not comply.

The feds will credit use of a number of devices, including insulation, in ceilings, walls, floors, for bare hot pipes and water heaters, on roofs and around forced-air ducts; storm or thermal doors and windows; caulking; weatherstripping; automatic set-back thermostats; more efficient furnace replacement burners; flue opening modifications; furnace ignition systems; and also meters that show energy savings.

Some items that do not qualify are heat pumps, flourescent lights, wood-burning stoves, replacement furnaces and boilers, hydrogen-fueled equipment, and "decorative" insulation, such as carpets, drapes, wood paneling and exterior siding.

The same conditions apply to "renewable energy source expenditures." Solar, wind and geothermal equipment also will eventually have to meet quality standards that have yet to be established. Excluded from credits is solar equipment for heating swimming pools (currently the biggest selling solar item), even if the pool is used to store solar heat.

Credits apply to both active and passive systems: collectors, thermostats, heat exchangers and storage rockbeds. However, components of passive systems that are structurally necessary to the house, such as thick walls, windows, skylights, greenhouses and roof overhangs, do not qualify.

Internal Revenue Service spokesman Ellen Murphy said persons who already filed their 1978 return but did not list energy-saving expenditures have until April 15, 1982, to file an amended form.

The energy-credit form, number 5695, is available at local IRS offices. Questions about energy credits can be directed to the IRS, although Murphy said, "This thing is so new, some people may not always have the answers."

Murphy expects regulations detailing the energy-credits system will be made public "shortly". CAPTION: Picture, no caption