Beginning next week in Maryland and perhaps later this year in Washington, customers who are delinquent in paying electric bills will find their service limited to just enough to barely light and heat their houses.

Potomac Electric Power Co. will begin installing an experimental device that limits the amount of current flowing into a house or apartment to enough to run a refrigerator, a single burner on an electric range, the motor on a gas or oil-fired furnace and a few lights.

Turning on appliances such as a clothes dryer or a hot water heater would boost use beyond the limit allowed, automatically shutting off the electricity. But limited service could be restored by pushing two buttons near the electric meter.

Pepco has been granted permission to use the device, called a service limiter, on an experimental basis in Maryland and is seeking to use the device in the District of Columbia. Pepco's application in D.C. has been opposed by the Office of the People's Counsel and the D.C. Energy Office.

"Pepco's objective in using the service limiters is to provide certain customers whose accounts are in arrears with the essential electric service, while strongly encouraging them to come in and make payment arrangements with the company," said Sam Boyd, general manager of Pepco's customer billing and credit division.

According to Pepco, the device would not be used in all-electric houses, where its installation would amount to cutting off the heat. Pepco would install the device when bills are more than 60 days overdue, the point at which the company would otherwise cut off service entirely. The device would be left in place 10 days, giving the customer that additional time to arrange a payment plan, Pepco said. After that, service would be terminated, unless the weather turned cold.

Pepco is prohibited in the District from cutting off service to customers during any 24-hour period in which temperatures fall to 32 degrees or below. If the weather got cold and stayed cold, the limited service would continue until either payment was arranged or the weather improved, said Pepco spokeswoman Nancy Moses.

The device is a collar that fits between a meter and the socket where the meter is installed; it allows 8 amps of electric power to be used. Devices that require enough electricity to exceed the limit and shut down service include hair dryers, clothes dryers, water heaters, dishwashers and electric ovens, Moses said.

"People would have to modify their life styles, but it allows people to have essential service without a disconnect," Moses said.

Pepco has about 30,000 customers who are 60 days or more in arrears on their bills, she said. The utility has ordered 200 of the devices so far, to be used experimentally on its worst cases, Moses said.

Moses noted that overdue bills amount to more than $1 million and are lower this year than they were a year ago. In fact, D.C. People's Counsel Brian Lederer said Pepco's uncollectable accounts have decreased steadily since 1978, when they were approximately $5.2 million, he said.

Lederer also pointed out that uncollectable bills account for only about a third of 1 percent of system revenues. What the proposal amounts to, Lederer said, is a backdoor way to get around the prohibition on cutting off service in cold weather.

Under Pepco's current system, customers who are late paying bills get a notice with their next bill that they owe for two months. If the bill is still unpaid 15 days later, they receive a notice that if there is no payment, service will be disconnected. In seven days more, customers receive a third bill noting that they owe for three months. That bill is a final disconnection notice.

At that point, the customer must be notified again, by telephone or in person, that the electricity will be shut off unless payment is arranged. Most customers who are actually disconnected generally arrange to make payment within 24 hours of the shutdown, Moses said.

Moses said that the devices have been used experimentally by Baltimore Gas & Electric, the Long Island Lighting Co., Mississippi Power and Light and Portland General Electric. The experience of those utilities is that 70 to 75 percent of customers whose service is limited arrange to pay within the 10-day period.