The Senate last night gave President Carter the $20 billion synthetic fuels bill he wanted, but with $14 billion worth of conservation programs he did not request.

A Carter lobbyist said the administration would not object to the conservation program, which grew on the Senate floor, but hoped it would be trimmed when the bill goes to conference with the House.

Overall, passage of the bill, 65 to 19, was a large victory for the administration, and leaves the oil windfall profits tax as the only major piece of Carter's energy package that has not passed the Senate.

Majority Leader Robert C. Byrd (D-W.Va.) hailed the bill as "insurance against future OPEC price increases" and as lessening the " dangerous dependence on foreign oil."

The crisis in Iran, where Americans are being held hostage and oil shipments curtailed, was a factor in one amendment the Senate passed that would require the president to begin filling strategic petroleum reserve, for which the United States stopped buying oil last year.

The amendment by Sen. Bob Dole (R-Kan.) would require the president to purchase the equivalent of 100,000 barrels of oil a day to fill the reserve. A motion to table the amendment failed, 53 to 36. The bill's floor leader, Sen. J. Bennett Johnston (D-La.), said he would attempt to modify or drop the amendment in conference.

One portion of the bill would set up a Synthetic Fuels Corp. to accelerate development of a commerical synthetic fuels industry producing any product that could be substituted for oil, such as shale, coal liquefaction and coal gasification.

The bill sets goal of 1.5 million barrels a day of oil equivalent fuel by 1995, and makes available a variety of financial assistance, including loans, loan guarantees, price guarantees, purchase guarantees and joint ventures. If all else fails, the bill allows the corporation to build three government-owned, contractor-operated syn-fuel plants.

Big oil companies fought hard to elimnate the three plants, which they consider interference and competition by the government in energy production. But an amendment to eliminate them was tabled, 47 to 44.

Carter originally wanted to spend $88 billion on synfuel production and finance it with the oil windfalls profits tax, but Congress scaled the amount down to $20 billion and funded it out of general revenue, at least until the fate of the windfall profits tax is known.

The Senate bill tentatively authorizes a $68 billion, second phase of synfuel development five years from now.

The conservation portion of the bill was added by the Senate Energy Committee in an attempt to win over those who believe that conservation, not synfuels, is a better means of cutting foreign oil use. As it emerged from the committee the bill provided $6.7 billion for weatherization, solar research, gasohol, geothermal energy and other programs.

When Senate got through with it, the conservation portion had grown to $14 billion.

The major increase was in gasohol, which went from $650 million in loan, price and purchase guarantees in the original bill to $6.2 billion in the Senate-passed version. Of this total $5 billion was added when Agriculture Chairman Herman Talmadge (D-Ga.) stuck on a 60-page bill his panel had been considering for months.

The bill also authorizes $3.35 billion in energy conservation loans to homeowners for insulation and weatherization and $2.4 billion in grants for weatherization for low- and moderate-income residents.

It also permits utilities to make loans to residential customers for conservation improvements, authorizes $50 million for training utility energy inspectors, requires an energy inspection when a house is sold, sets up an experimental program to charge utilities for insulation improvements, and authorizes $120 million to speed research into energy efficiency for industrial processes.

It authorizes $750 million for a solar bank to make loans for homeowners and small businesses to install solar equipment, provides $750 million for geothermal energy, $100 million for wind energy and sets up a conservation bank to handle the loans.

House-Senate conferees on an Interior appropriations bill also agreed yesterday to spend $1.35 billion to aid the poor with their home heating bills. y