IS THE electric car the long-awaited cure for the country's energy deficiency anemia? The president of Gulf and Western Industries, which unveiled its new battery with appropriate hoopla this week, apparently thinks so. He described the breakthrough as "one of the most meaningful developments since the turn of the century." Since this puts the electric car in the same class with nuclear fission, computers and antibiotics, the claim deserves some attention.

Battery cars were abandoned years ago because gasoline could store much more energy in a far smaller space and with less weight. For them to be competitive, a way had to be found to drastically lower battery weight and to lengthen battery life until it was about the same as the life of the car. Gulf and Western's new design does both. It has four times the energy density of conventional lead-acid batteries, should not need replacement and can power a car for 150 miles at 55 mph between recharges. The design is a true breakthrough, though in a few years it is likely to look primitive: sophisticated battery research is ony just getting under way.

The new design shows that practical electric cars can be built in the near future. The question remains whether these cars will substantially improve the country's energy balance. Though batteries can be nearly 100 percent efficient, the generation of electricity is inherently inefficient. A comparison reveals that an electric car uses about twice as much energy per mile as a 40 mpg gasoline-powered car. On the other hand, electricity cars can therefore displace vulnerable imported oil, probably at a lower cost.

Fuel-efficient automobile fleets of the future are likely to reflect a profound change in what is called the "vehicle mix." Most of today's cars are designed to do a great many things -- carry many passagers and lots of luggage, accelerate very fast and cruise at high speed -- which they seldom do. Recent studies indicate, for example, that there are only one or two passengers in the car in 92 percent of trips to and from work, and in 78 percent of all trips. The average family in the year 2000 is therefore likely to own cars tailored for the purpose for which they are most often used.

In this new kind of car fleet, the electric vehicle could play a big role -- especially as delivery trucks and two-passenger urban commuter cars. With an aggressive production effort, they might save 1 million barrels of oil a day by the turn of the century. But electric cars are not a whole answer. They cannot substitute for gasoline-fueled cars in many other uses, and their development therefore does not obviate the need for far greater efforts to increase the fuel efficiency of the internal combustion engine. That remains the No. 1 priority.