SALT LAKE CITY (AP) — Questar Gas is double checking all of its meters to ensure the equipment is sending the company the correct information about how much natural gas each customer has used.

Although the utility says it won't be done rechecking all 840,000 meters in its system until the end of the year, it is confident it already has identified the vast majority that were sending wrong information, which led to the additional billing of some customers.

Questar 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, though, the utility discovered about 500 transmitters were underreporting natural gas use.