When Mrs. Clarence Larson of Bethesda visits a friend's house for lunch, she plugs her electric car into a standard wall socket so she will have a lively charge to drive home on.

Her husband uses the car for runs into Washington when he has business there. The Larsons live about 14 miles from the Cosmos Club, where Larson park the car and charges it up while he has lunch and then goes about his business using the Metro for aroundtown transportation.

This means that the car's 30-mile range is just right for the Larsons. They use it for shopping and running about town at speeds of up to 35 mph, and they have a station wagon and a couple fo Volkswagens for more demanding trips.

Larson, a retired commissioner of the former Atomic Energy Commission who always has been interested in the development of the nation's energy resources, converted the 1968 green karman Ghia to electric power two years ago with the help of his son, Lawrence, 19.

They bought the car for $1,000, spent another $1,000 for special instrumentation and controls and $500 for heavy-duty batteries, which have had to be replaced once so far.

There are many problems with the car, and while the Larsons have made it part of their lifestyle, they realize that widespread use of electric cars cannot take place until they are more practical.

"I would say it is the equivalent of a gas-driven car of 1920." said Larson. "The ordinary intelligent laymen could drive these cars today. But it means you have to put up with some inconveniences."

These include remenbering to plug it in, adequate but not very good acceleration, and the constant worry about whether you will hit too many traffic lights and not have enough power to get home.

Stopping for a light, he said, takes more than a mile off his 30-mile range "so you try to keep sliding through the lights."

"I think drivers (of electric cars) will have to take a course," said his wife. "If I'm in a hurry I'll accelerate quickly, and I can just see the voltmeter going down." She said she often did this when she first drove the car and before she learned how much it drained the batteries.

Recognizing problems like these. Congress late last year passed over President Ford's veto of $160 million measure authorizing development of electric cars. Eventually the government will buy up to 7.500 electric cars for testing and demonstration. Ford had called the measure premature.

The Energy Research and Development Administration announced this spring that General Electric Co. and Research Manufacturing Co. were selected to build experimental electric cars using improved lead-acid batteries with enough power to drive 75 miles at speeds up to 55 mph.

"Improved batteries are the key." said Larson. "Ordinary car batteries aren't good enough for an electric vehicle. They won't last 60 days."

Larson said he did not pamper his first set of batteries enough and they did not last long. Now he has 10 special electric vehicle batteries made by Globe Union. They resemble regular car batteries but are more powerful.

Larson says they should last three years with proper care. The main thing is not run them all the way down to "deep discharge" before charging them again. Also, it is best to charge them slowly at a regular electrical outlet rather than quickly with special equipment.

Larson said an electric car gets about three miles per kilawatt hour, although his own home-made car does not do quit that well. His batteries hold 10 kilowatt hours.

Since a kilowatt hour costs about 5 cents, he said; he can go 30 miles for about 50 cents. A car that fot 30 miles to a gallon of gas would cost a bit more to go that distance.

Larson conceded that the special costs of his electric car - $1,500 in special equipment plus periodic battery changes - would have to be figured on top of the fuel costs.

It takes his car about seven hours to put on a full charge, Larson said. Because the batteries charge more rapidly the lower they are, he can put on a half charge during the few hours he spends luching and doing business downtown.

Each time he charges his batteries at the Cosmos Club Larson sends the club a check for 10 cents a kilowatt hour - double the normal amount; for their trouble.

"Get in," he said after unplugging a yellow extension cord from a plug in his gas tank.

The car ran with a high-pitched whine. In back, where the gasoline engine had been removed, was a box containing heavy-duty electrical circuitry. The rows of batteries were under the back seat and in the front trunk space.

The batteries weihg about 600 pounds and the entire car about 1,700, Larson said. He said a lighter car would go farther, but his wife noted that other drivers tend to resent smaller electric cars that "look like golf carts."

Larson eased into traffic. He seemed jittery and tried to make as many lights as he could. Arriving at The Post building, he figured he had enough juice to make it home.