Improvements in energy efficiency, otherwise known as conservation, allowed nationwide production of energy-related goods and services to rise 2 1/2 times more between 1973 and 1978 than it otherwise would have, according to a report from the Union of Concerned Scientists.

The Massachusetts-based group, which is active in opposition to nuclear power, offered a five-point program to boost efficiency further without any major alterations in the American lifestyle.

The so-called "easy path energy plan" would allow a 12 percent reduction in oil imports below present levels by 1985, a 50 percent reduction in nuclear power use, the creation of a reserve oil production margin to cushion import cuts, and the elimination of any synthetic fuels program, the report claimed.

Author Vince Taylor, a Massachusetts energy economist and consultant found that if energy use per unit of production had continued at the same rate from 1973 to 1978, the country's energy use would have jumped by 10.5 quads over that period. (A quad equals roughly the energy in 183 million barrels of oil.)

Instead, he wrote, energy use rose by 2.9 quads, so that efficiency saved the rest. In other words, Taylor explained, while increases in gas, nuclear and hydropower generation accounted for 2.9 quads of new energy, efficiency increases saved 7.6 quads that otherwise would have been spent for the same amount of production.

"In almost all sectors of the economy, strong trends toward improved energy efficiency are established or will soon begin," the report said. Taylor criticized Carter administration energy plans as "cast from the same old mold" of trying to expand energy supply instead of reducing demand. The "easy path" plan would simply speed up the rate of application of existing energy-saving methods, he said.

The study claims to be the first major effort to put numbers on the effects of the reduction in energy demand that began with the Arab oil embargo of 1973. With no further acceleration of conservation, 1985 industrial uses of energy will still be 3 percent below the 1973 level, even though industrial production will be 37 percent higher, the report predicted.

Airlines will carry 100 percent more passengers in 1985 than they did in 1973, but their energy use will go up only 15 percent, Taylor said.

In 1985, demand for energy services such as transportation, industrial production and heat will be one-quarter larger than in 1978, Taylor predicted. With the "easy path" plan, that demand can be met with an actual reduction of about 1.6 quads in overall energy used, Taylor said. The country now uses 77.5 quads per year.

The plan suggests the following changes:

Revise Environmental Protection Agency mileage tests to a more accurate reflection of autos' true performance, plus a stiffened mileage standard for light and medium-weight trucks.

Increase mandatory heating efficiency standards for old and new buildings.

Modify utility rate structures to encourage homeowner electricity use when overall demand is lightest.

Reverse policies encouraging utilities to switch from gas to coal, allowing more use of gas.

The total program can extend the lifetime of remaining conventional fuels beyond 2025, "providing sufficient time for an unhurried transition to safe, renewable energy resources," the study said.