Traveling in an unmarked car, the two-man team of Ken Grant and Jim Garvey, stopped first at a lower Manhattan restaurant where an employee said that only the absent boss had the key to the locked meter room.

The targets had been selected from a computer list of business and residential customers whose customary power use had abruptly dropped by a substantial percentage - up to 50 percent in some cases. How the recent security measures are being applied - or at times frustrated - was illustrated the other day as two meter inspectors made their rounds in Manhattan. ''There's an awful lot of heinous crime going on,'' he said. Stevens said it was difficult to interest lawenforcement authorities in the utility's problems. 'They Can Do More'Д«arry Kluger, an assistant district attorney in the Bronx who is in charge of the arson and economic crime bureau, said he had prosecuted some of Con Edison's major power theft cases, ''but I happen to think they can do more.'' Some of the cases the utility recently brought to him, he said, dated back as much as three years.Д¬on Edison's Mr. Nonetheless, he said, the number of cases last year was down from a 1980 peak of 14,000, and the utility expects the total to drop further as the new measures take effect. He estimated that the loss from thefts that went undetected might have been twice the $7 million. One manufacturer is responsible for $250,000 worth of thefts, the utility said. Commercial customers, including landlords, accounted for 20 percent of the cases, but 80 percent of the dollar losses. The recent measures, utility officials say, are aimed at the half of 1 percent or so of the 2.8 million commercial and residential customers in New York City and Westchester County who have been found to risk prosecution and electrocution to siphon off electricity and gas.ДЄbout 80 percent of those caught were residential customers, although they accounted for only 20 percent of the dollar losses. Some of the investigations touched on several Con Edison workers, but employee dishonesty was not a major factor in the cases, he said. In addition, utility and lawenforcement officials say, legislative changes have made prosecution easier. For large commercial users, Con Edison has also introduced a new solid-state meter with a built-in alarm that signals the computer every time the equipment is opened. ''You can saw these locks till your arm falls off,'' he said. Stevens, the utility's assistant vice president for central customer services. More than 57 percent of the utility's nearly three million meters are now secured with some form of the special hardened steel locks developed by Con Edison, and all of the meters will have the locks in about two years, said Robert B. The new security program includes a computer system that automatically prints out cases of sudden suspicious drops in power consumption a cadre of 140 meter inspectors, in addition to the 600 regular meter readers, who visit the sites pinpointed by the computer, and patented new locks to bar tampering. ''You have to be a maniac to fool around with steam,'' said Lawrence Kleinman, a utility spokesman. Steam, on the other hand, is never stolen. Running the gas through pipes used for oil creates the danger of gas explosions. In addition, some landlords of oil-burning apartment buildings were found to be altering their furnaces and illegally tapping Con Edison gas lines. The most common methods of tampering, which are easily detectable by inspectors, are removing the meter and reinserting it upside down to make the kilowatt clock run backward, turning back the clock hands or simply disconnecting the meter altogether. But the company says a security program begun four years ago is now paying off significantly as a deterrent and in recovered funds. Consolidated Edison officials say the utility investigated 88,942 cases of suspected power theft last year and caught 12,000 customers stealing $7 million worth of electricity and gas through tampering and illegal hookups that bypass the company's meters.

Edison meter lock key