The man in charge of coordinating President Carter's energy plan in the House is considering several additional proposals, including a 3-cent gasoline tax to put more energy savings into the bill.

Rep. Thomas L. Ashley (D-Ohio), chairman of the House Ad Hoc Energy Committee, said the legislative committees have done a "remarkable job" of processing complex legislation in a short time. But since the Ways and Means Committee rejected Carter's standby gasoline tax that could have risen to 50 cents a gallon in 5-cent annual steps if the nation's drivers failed to meet specified goals, the President's objective of reducing gas consumption 10 per cent by 1985 cannot be met unless some alternative energy saver is found, Ashley said.

He said Congress should took carefully at auto usage. Forty per cent of gasoline is used to drive people to and from work, many of them one to a car, he said.

Ashley said one possibility he has been considering is a 3-cent gas tax to be used to encourage use of mass transit and car pooling. Another possibility would be to close service stations on Sundays, he said. Ashley said he isn't committed to either. Last year the House rejected a 3-cent gas tax.

Next Wednesday the ad hoc committee will meet to begin its task of assembling the energy legislation, which has been handled up to now by five legislative committees, into one bill to be sent to the floor. Ashely's committee cannot change the bill, but it can offer amendments on the floor. And he is saying he will ask his committee to approve some energy-saving alternative to the dead standby gas tax, though he has not yet been asked by the administration to do so.

Ashley said he is still committed to Speaker Thomas P. (Tip) O'Neill's schedule of pushing the bill through the House before it begins its summer recess on Aug. 5, but conceded that will be "very difficult."

There have been White House discussions for a couple of days, an official said, about whether the administration should try to strengthen the bill. If it does try to make changes, the probable areas would be the taxes on gas-guzzling big cars and on industrial use of oil and gas, both of which Ways and Means weakened, rather than the rejected gasoline tax and price-reducing rebate on small cars, he said.

The Senate Finance Committee will delay action on the tax parts of the President's plan until the House sends its bill over, a member of the committee staff said.But the Senate Energy Committee, which handles all nontax parts of the package, will begin voting on nontax portions of the bill next week and may send it to the Senate floor as several different bills, a committee staff aide said.