We recently received a gas bill from our local utility, PSE&G, that was surprisingly high. That's because we weren't home when the professional meter reader was in our neighborhood, and the utility estimated our gas usage for that month. We got a bill for over $300 in estimated gas usage, when our normal amount might be closer to $50!
After a frantic phone call to the utility, we found out the estimate was based on the company's formula which is a follows: They take the highest reading for that particular month over that past three years and then apply a premium. (We weren't told what that premium is.)
The trouble is, we're often not home when the meter reader comes to the door. Last year, we had several months of estimated charges that were too low, and then in June they took an actual reading and we were socked with a legitimately high gas bill. Having a monthly reading would have helped our cash flow back then.
That was bad enough, but the problems of the past revisited us in the present. This year, we had an actual reading in April that was "normal." Then, there was a "normal" estimate in May. But we missed the June reading, and therefore, the utility's formula kicked in. They based the current month's charges on last year's high reading for June and added the premium. The bottom line was the more-than $300 in gas charges.
You can see how this formula most often works in the company's favor—especially when you're trying to conserve energy and use less gas than your were several years ago! If you know you won't be home on the day your gas company representative is in your area, you can make an appointment to have someone come out and read your meter.
Your second best option is to call in your meter reading, but accuracy is best served by having a professional read the meter if at all possible.