CONGRESS IS expected to act this week on a bill that would allocate $4 million to install solar energy-heating, air conditioning and water-heating systems in U.S. diplomatic and consular offices abroad.

The Foreign Mission Solar Energy Demostration Act was introduced in Congress in February. Congressional action is expected in time for he money to be included in the 1979 general State Department budget.

Two examples of the benefits of solar energy were begun in 1975 in Israel, a sunny land where solar hot water heaters are common. Two Foreign Service officers in Tel Aviv installed solar energy water-heating systems in their government-owned homes at a cost of $1,200 per unit.

Each unit has saved between $300 and $400 per year in heating water over the previous use of electricity, according to James L. Schoonover, a mechanical engineer with the State Department's Office of Foreign Buildings, who worked with Charles Honya, the general services officer at the embassy in Israel at the time. The bill was presented to the House by Rep. James M. Jeffords (R-Vt.) and co-sponsored by Rep. Leo J. Ryan (D-Calif.). Rep. Jefforts said last week he expected the bills to pass without any trouble.

Schoonover says 11 major solar energy projects (heating and air-conditioning embassies) are being considered at a cost of $4.4 million together with 130 domestic water-heating projects at a cost of $524,000. These amounts will have to be trimmed perhaps to fit the $4 million amount in the bill. Certain solar energy units are already under way in Mauritania and Pakistan. Projects are being discussed for Niger, Senegal, Egypt, New Zealand, Bangladesh, Malawi, the philippines and Kenya.

The bill was been introduced in the Senate by Sen. Clifford P. Case (R-N.J.), co-sponsored by Sen. Charles H. Percy (R-Ill.)

Jeffords' bill is a part of the State Department's financial authorization act for 1979 starting Oct. 1, 1978. It suggests that all projects selected shall be adaptable to local resources, climate and economic conditions of the host country, and must be available for inspection by officials and citizens of the host country.

When he introduced his bill in February, Jeffords said it "is designed to help us to move to a position of leadership" in solar energy technologies. Case stressed much the same points in the Senate and underscored the need for America to help other countries solve their energy problems:

"At the same time it is designed to make U.S. diplomatic posts more energy self-sufficient and less reliant on interrupted local energy supplies, thus providing an added degree of security vital to the operation of the sensitive systems with U.S. missions abroad."

Percy saw solar energy as an antidote to the use of too much nuclear power abroad. "It is my belief that recent Third World interest in nuclear power could be diminished," Percy told the Senate, "if the superiority of nonnuclear options were demonstrated in an objective way. The installation of solar and other renewable energy sources in U.S. buildings in these countries couldprovide such a demonstration."