House and Senate conferees finally agreed yesterday on an energy tax bill that contains about $1 billion in tax credits to encourage energy conservation and a watered-down version of President Carter's proposed tax on the sale of gas-guzzling cars.

But, as expected, the conferees, went along with the Senate in rejecting his two big energy-saving taxes on domestic crude oil and industrial use ooil and gas.

The bill provides tax credits of up to $300 for home insulation, up to $2,200 for installation of solar heat in homes and an additional 10 percent investment tax credit for businesses purchasing energy-saving equipment.

The focus of the energy fight will shift to the House today for the fianl round in the 18-month fight for passage of an energy package, which Carter called the most important domestic issue facing this Congress. Much of his original bill - such as taxes and regulation of utilities and industry to save oil - has been eliminated or severely restricted.

The major item remaining is the phased natural gas by 1985. In an effort to push deregulation through the House, Democratic leaders today will ask the House Rules Committee for a rule to group together all the energy measures in an effort to help pass the controversial natural gas section by attaching ot it the attractive federal aid goodies in other sections.

The parts the Rule Committee will be asked to bundle together include $900 million to insulate schools and hospitals, grants of up to $800 per household to help poor people insulate homes, ordering settling of major home appliances, requiring state regulatory bodies to consider ordering electric utilities to offer cheaper rates to customers for off-peak use electricity and a regulatory program to shift industry and utilities from use of oil or natural gas to more abundant coal.

Opponents of the natural gas compromise will fight in the Rules Committee and on the House floor to try to split off the gas issue for a separate vote. The final House vote is scheduled tomorrow or Saturday.

Yesterday's action winning conference agreement on an energy tax bill consisted of the Senate conferees meeting alone and accepting an offer made by House conferees a week ago. The senators had been tied up since then with Senate action on the big tax-cut bill.

The gas-guzzler tax would begin a year from now with the sale of 1980 model cars. In the first year, a car getting less than 15 miles per gallon would be taxed from $200 to $550. The tax would increase each year until 1986, when the maximum tax would be $3,850 on sale of cars getting less than 12.5 miles per gallon.

Because of penalties assessed manufacturers under existing law if their first average fails to meet mileage standards, few low-mileage auto are expected to be built in this country by then.

Sen. Russell B. Long (D-La.), chairman of the Senate conferees, was asked if he thought the energy tax bill would help encourage people to save energy. "It will help somewhat," he said. "Not much, but some."

Senate conferees approved the final version 10 to 2. Sen. Bob Dole (R-Kan.) had wanted to further water down the gas-guzzler tax. Sen. Clifford Hansen (R-Wyo.) had wanted to redefine low-production stripper wells to bring more into this category, which is not subject to price controls.