The Senate Finance Committee yesterday approved a sharply scaled-back package of energy tax credits, effectively scrapping an earlier decision to triple homeowners' tax credit for inslulation.

Nearing completion on President Carter's proposed "windfall-profits" tax bill, the panel decided to continue the 15 percent home insulation tax credit. It voted earlier to boost the credit to 50 percent.

At the same time, the panel approved a sizable new tax credit for installation of home solar energy equipment, and it voted to extend the 15 percent home insulation credit to purchases of heat pumps, wood stoves and other items.

It also voted to allow users of gasohol 10 times the tax break they now receive by providing them a tax credit of 40 cents a gallon in place of the current exemption from the 4-cent-a-gallon federal gasoline excise tax.

The panel's cutbacks yesterday were prompted by budgetary considerations. In earlier voting, the committee had approved $99 billion worth of tax credits, outstripping the revenue the windfall-profits tax would have raised.

Yesterday's cutbacks would pare the energy tax credits for homewoners to $9.2 billion for the 1980s, down from an original package of $46.9 billion. The committee begins work today on energy tax credits for business.

Panel Chairman Russell B. Lond (D-La.) has said he hopes to hold the total of residential and business tax credits to about $25 billion, or about a third of the $76.8 billion the tax is expected to raise over the decade.

The committee voted on Tuesday to use $30 billion of the revenues for energy aid to the poor and for a tax credit for families earning $20,000 or less. The panel has slashed the tax to two-thrids that voted by the House.

The tax credit for solar energy that the Senate panel approved yesterday would increase the solar tax credit to 50 percent of the first $2,000 in expenditures and extend it to cover second homes.

The current 15 percent home insulation credit would be extended to cover heat pumps, wood stoves and replacement furnaces. The committee also voted to allow a 25 percent tax credit for installation of coal furnaces.