While American comment on President Carter's energy proposals has focused on the gas-guzzler aspects - high taxes on gasoline and horsepower - European experts give the overall program high marks and suggest that its other provisions are far more important.

"The Carter energy plan moves to United States back toward the head of the class on energy conservation," said J. Wallace Hopkins, deputy director of the International Energy Agency. "The United States will rank well up with the best of the IEA countries now."

Europeans look beyond the gasoline taxes that Carter has proposed because of their experience of paying a dollar or more per gallon in taxes for the past decade - and finding that high gasoline taxes do not significantly reduce driving or dramatically affect life-styles.

"Nobody has found the saturation point. We don't know what the price is that will make people leave their cars at home," said an economist for the Organization for Economic Cooperation and Development.

In fact, if President Carter's 50 cents-a-gallon tax were imposed today, instead of being phased in over a decade, Americans would be paying about half the $2 to $2.40 per gallong prices that prevail in Europe.

"The gasoline and big-car taxes will get people to shift down to smaller and / or lighter automobiles, if Europe and Japan ore any indication," said the OECD economist. "Is that such an upheaval?" The group is a research organization for the industrial nations of Europe, Asia and North America.

With little oil of their own and uneconomic coal deposits, Western Europeans are accustomed to restraints and high taxes on energy. Ideas similar to Carter's proposals have been suggested or tried here.

Carter's plan meets 12 of the Internation Energy Agency's 13 major conservation recommendations and may cover others when details are worked out Officials of the agency, the Common Market and European governments are praising the plan privately and publicly.

The energy agency was formed after the 1973 Arab oil embargo to fight future supply disruptions. It includes 18 of the world's largest oil-importing industrialized countries, and its most recent staff reports have been critical of energy waste in the United States.

European public reaction to the Carter proposal has been to suggest that Americans relax, that the future works, and it is called Europe.

But significant differences energy consumption exist between Western Europe and Japan on the one hand and in the United States on the other.

Most European governments have used high gasoline taxes to earn revenue rather than to discourage consumption. That may account for much of the skepticism that the relatively moderate (as seen from Europe) gasoline tax is vital to the Carter Plan.

Carter is also taking a new approach in trying to return gasoline and automobile taxes to tax payers through rebates and credits. European governments, far more dependent on sales and excise taxes, put gasoline tax revenues directly into operating budgets and lack Carter's flexibility to ease the burden on the public.

In Europe, high taxes and the quintupling of crude oil wholesale prices since 1973 have helped curb European carmakers tendency in the 1960s to balloon their models up to American scale.

Differences in roads, population centers and life-styles make U.S.-European comparisons difficult, but OECD figures show that Americans drive twice as much per capital as French motorists and use more than four times as much gasoline - 484 gallons to 109 gallons in 1975. That means that Americans could probably save 3 million barrels of oil a day by switching to the smaller automobiles driven in Europe.

Europe's experience indicates mixed prospects for parts of Carter's energy plan:

The expense and difficulty that European countries have had in beginning to build the 90-day stockpile that the International Energy Agency is requiring of its members by 1980 suggest that the Carter administration may have underestimated the problems of building a 180-day stockpile.

Charging consumers more for power at busy times of the day is common in Western Europe for households and industries, and its inclusion in the Carter plan is endorsed by energy agency officials.

European use of coal declining rapidly before 1973, has stabilized. British Petroleum and Shell have searched as far as Australia and South Africa for coal for Western Europe, which imports from Poland now.

European governments tend to mandate rather than give the incentives the Carter plan proposes for conservation. France, for example, has inspectors who can fine offenders who let thermostats go above 68 degrees in public buildings.

Carter's intention to let the price of U.S. domestic oil rise by 1980 to the price set by the Organization of Petroleum Exporting Countries, has most interested energy economists.

"Energy has to be priced at replacement cost, or replaced," said Hopkins of the energy agency. "President Carter has correctly recognized that there is no 'quick fix' and no immediate replacement. So he is going the realistic route."

The gradual rise to the OPEC price is supposed to squeeze industry into new conservation efforts and encourage domestic exploration and production.

"Industry is where you get your greatest saving because costs have to be kept down there," Hopkins said.

Energy planners here endorse Carter's view that the United States and Western Europe are heading for "catastrophe" unless crude-oil demand falls. The OECD's energy-planning assumptions published earlier this year coincide with the U.S. Central Intelligence Agency's estimates of supplies released last week.

"If Carters plan works, you probably won't see much visible change in the world economy. The 3 million barrels of imports he wants to cut will keep demand and supply just about in balance in 1985," said an OECD planner. "But if he fails, oil-consuming nations are going to face absolute shortages and enormous price rises, and before 1985."