House and Senate conferees on President Carter's energy bill reachad tentative agreement yesterday on how to help insulate schools and hospitals and on requiring standards for major home appliances.

The legislation would authorize $900 million over three years to pay up to half the cost of weatherproofing schools and hospitals. It would also authorize $65 million to survey the insulation needs of municipal buildings, and of nursing homes, orphanages and the like operated by civic and fraternal organizations.

This would supplement the program approved by the conferees last week under which local utilities would help homeowners insulate their homes. A tax credit of up to $400 has been approved by the House and the Senate Finance Committee for homeowners who insulate.

The conferees agreed that half the school and hospital insulation money would be distributed to states according to population. For the other 50 per cent the formula would take into account climate and cost and availability of fuel. No state could receive more than 12 1/2 per cent of the funds, and none receive less than 1/2 per cent.

The requirements that major home appliances meet energy standards would resemble the 18-miles-per-gallon requirement for auto makers' fleet averages that takes effect this year.

The Department of Energy would have two years to write standards that 13 specified appliances such as furnaces, stoves, refrigerators must meet. The department could set standards for others at its discretion.

Today the Senate is scheduled to begin debate on the bill that came over from the House as Carter's energy tax bill but was transformed by the Senate Finance Committee into a taxless tax credit bill to encourage production and conservation of energy.

Carter's supporters will try to strip out most of the estimated $40 billion in tax credits that the Finance Committee bill would give away by 1985.

The committee rejected Carter's proposed taxes on domestic crude oil, industrial use of oil and natural gas, and gasoline-guzzling cars. But Committee Chairman Russell B. Long (D-La.) hopes to put the crude oil tax back in the conference with the House, in return for preserving some of his tax credits.

Instead of taxing the gas-guzzler, the Senate voted to ban sales of low-mileague cars by 1980.