Supporters of solar energy, five members of Congress and the State of New York sued President Reagan and five Cabinet secretaries yesterday, charging that they illegally impounded money appropriated for the congressionally created Solar Bank.

In a lawsuit filed in U.S. District Court for the Southern District of New York, the coalition charged that Reagan is illegally ignoring a congressional mandate to get the bank going. The bank would provide loan subsidies to consumers for conservation and solar energy improvements.

When Congress adopted the legislation creating the bank, "It was a command to get the money out," said Rep. Stewart B. McKinney (R-Conn.), one of two Republicans suing the Reagan administration. "I've never seen a case where we have been really so explicit about--'Do it!'--and they're not doing it, so we're suing them."

According to the lawsuit, none of the $21.85 million appropriated for the bank this fiscal year has been spent, no meetings of two advisory committees have been convened, no regulations have been published and no staff has been hired since the staff was dismissed in January 1981.

"After reviewing the Bank Act, I find that I cannot support its programs. I do not think that further federal involvement in this area is either necessary or desirable," Housing and Urban Development Secretary Samuel R. Pierce Jr. wrote Energy Secretary James B. Edwards Jr. in March 1981. Pierce, Edwards, Office of Management and Budget Director David Stockman, Treasury Secretary Donald T. Regan, Agriculture Secretary John R. Block and Commece Secretary Malcolm Baldrige are named as defendants in the suit.

The Reagan administration has asked Congress to rescind funding for the Solar Bank. That request, which requires approval by a majority in both houses by April 21, already has been rejected by the House Appropriations subcommittee that deals with such issues, said Alan Miller, an attorney for the Natural Resources Defense Council. Even with that request pending, the administration is required by law to spend money and publish regulations as mandated, he said.

McKinney said that, even if the attempt at recission fails, he expects the administration to continue its inactivity with the Solar Bank. "We just have to assume that the administration has made the decision to break the law," he added. "They're breaking the law now, and they'll break the law then."

Steven Ferry, chairman of the Solar Lobby, which organized the coalition, said that the Solar Bank program is "the energy safety net under a broad group of our population." Because the money appropriated would be used to pay a portion of the interest or principal on loans for solar installations, the value of the improvements it supported would be greater than the $21.85 million, he said.

The Reagan administration is asking for the recission of funds for the bank under the provisions of the Impoundment Control Act, adopted in the wake of the fight 10 years ago when President Nixon refused to release funds for antipoverty, environmental and other programs.

The plaintiffs in the lawsuit include the Cities of Philadelphia and St. Paul, the League of Women Voters, the National Audubon Society, NYPIRG/Citizens Alliance, the National Association of Solar Contractors and First Hub Credit Union.