SOLAR ENERGY is a highly practical idea to which this country is still paying remarkably little serious attention. The uncertainties of the various fuel and power supplies have now reached a point at which prudent people would be wise at least to start thinking about solar possibilities for their own homes.

Prudent people tend to be put off solar energy, however, by the vast freight of political and philosophical enthusiasms that some of its friends have loaded onto it.But it is permissible to use the sun's power to heat your bathwater without necessarily subscribing to the whole granola ethic. In order to install a solar panel, you are not required to believe that small is beautiful, or that decentralized economies are better, or that bean sprouts are best. If you are simply looking for a source of heat that diminishes your vulnerability to future OPEC price increases, and nuclear misadventures, you might reasonably try thinking solar.

There's plenty of room for both public and private initiative. The solar opportunities are greatest in building new houses, rather than converting old ones. Instead of installing solar panels, which are expensive, a builder can achieve high efficiencies simply through careful siting and long-established construction techniques. As this newspaper recently noted, one Northern Virginia builder, Harry Hart, is putting up houses that appear to use about one-fifth the normal amount of fuel oil.

The Department of Energy is now drafting performance standards that will make such houses cost a bit more to buy, but vastly less to operate as the years go by.

Solar energy has its limitations. Many kinds of existing buildings would be difficult to adapt to it. Solar generation of electricity, on a commercial scale, is still far in the future. But in the past the greatest inhibition to residential use of solar heat has been the extreme cheapness of its competitors - oil, gas and electricity. Suddenly the competition is not so cheap.

If solar energy seems altogether impractical to you, reflect for a moment on the unappealing choices among the more familiar sources of heat and power. Burning coal in large volumes creats serious health hazards. Nuclear reactors offer dangers of another kind. The oil supply is increasingly instable. The unavoidable choices get worse as the national demand for power increases. If demand slacks off a little, those choices become much less intractable and menacing. That much can be accomplished by common sense, conservation and sunshine. In the great forbidding morass of American energy policy (and non-policy), that is one of the few genuinely reassuring possibilities.