Questar Gas Co. said this week that it plans to spend the rest of the year monitoring all its gas meters in the wake of its discovery of some miscalibrated transponders.

Questar spokesman Darren Shepherd said Friday that as part of the company's monthly automated meter reading process, the utility would verify that meters and attached transponders are synchronized properly and relaying accurate information for use in customer billing.

Shepherd said although Questar won't physically inspect all 840,000 meters in its system individually, the company has updated its software to allow personnel in trucks that obtain meter readings electronically to verify the proper functionality of the equipment. The utility also conducts on-site individual inspections of each meter every three years.

Shepherd said the problem initially arose from some meters that were fitted with transponders calibrated for use with a type of meter typically found on larger homes and small commercial businesses with numerous appliances. The larger meters allow for gas flow greater than that allowed by the normal meters fitted on most residential homes, he said.

Questar's transponders on the large meters "indicated one foot of gas, so for every two feet of gas going through the meter, the device was sending a signal back saying it was only one foot of gas," he said. The miscalculation resulted in several hundred Questar customers getting letters in recent weeks indicating they owed hundreds, and in some cases thousands, of dollars in unpaid gas usage.

Shepherd said Questar is confident it has already identified the vast majority of transponders that were sending wrong information, which led to the additional billing. He said the utility started installing transponders, or transmitters, on its meters about 10 years ago in the hopes of eventually eliminating the need for meter readers going to each home.

In November, the utility discovered about 500 transmitters were underreporting natural gas use. Since that discovery, Shepherd said the utility has isolated the exact type and brand of meter that was experiencing the problem and made what the company believes is the necessary correction.

"Now we can target the various brands of meters during each billing cycle," he said. Each month, Questar will focus on certain meter types to guarantee accuracy of its electronic data collection process, he said.

"We're doing everything we can to ensure that customers get accurate bills every month," he said.