As the temperatures drop, utility bills rise, and Questar Gas customers may find their next bills as much as 50 percent higher than a year ago due to high usage.

The per-kilowatt electricity prices won't be changing that soon as a result of high usage in November, but Utah Power probably will seek a general rate increase from the Public Service Commission in early 2001.

The culprit? A November weather pattern that could result in the coldest November in the Salt Lake Valley since records were first kept in 1928.

"We had been saying that some customers will experience differences in bills of 50 percent, but now we're saying most customers," Questar spokesman Chad Jones said. "It's because of the weather. In 1999, it was slightly warmer than usual. Now it's significantly colder."

Questar received a 3.8 percent increase in a general rate case this year and a pass-through increase of 12.7 percent. Pass-through rates reflect the price for gas the company purchases from outside suppliers, with no markup.

With that 16.5 percent rise, the company had expected the typical bill to rise 15 to 20 percent. But that was based on last year's usage. As usage rises, so do bills.

Through Friday, Salt Lake City's mean temperature was 30 degrees, nearly 12 degrees colder than the typical November. To keep up with demand, Questar delivered 16.5 million decatherms to its customers during the first 26 days of the month. That's 47 percent higher than for the same period last year, when the figure was 11.2 million decatherms.

Utah Power customers, meanwhile, may eventually see a rise from the current rate — about 6 cents per kilowatt hour — next year. Its parent company, PacifiCorp, is using a deferred accounting procedure to track higher wholesale power costs and will use the information in future rate cases. It started tracking those costs in October.

The company has predicted the deferred amount could total $165 million during a 12-month period, depending on the degree of future power price volatility. Utah's share is estimated at $67 million.

In 1999, the company's power purchases — from long-term contracts and wholesale purchases — accounted for 34 percent of its power sources.

Demand has outdistanced generation during peak usage times, leading to wholesale electricity price spikes, spokesman Dave Eskelsen said. But because PacifiCorp's tracking of wholesale costs began in October, the company absorbed the high wholesale prices experienced this summer.

Questar buys about half its gas on the open market but has relied on its own wells to keep price increases from being as high as those experienced by gas customers elsewhere in the United States.

The open market volatility has led St. George to continuously use diesel generators for power because they provide cheaper power than is sold on the open market. The generators were installed for use as an emergency power supply but have been providing power to St. George, Hurricane, Washington and Santa Clara.

Twin City Power in Hildale also will purchase power from St. George, which owns 84.73 percent of the plant. Hurricane, Washington and Santa Clara own the remainder.

Power and gas usage will be on the upswing if forecasts from the Climate Prediction Center of National Oceanic and Atmospheric Administration in Maryland become reality. The center is predicting the temperature in Salt Lake City in January will be 4 to 6 degrees cooler this winter than the historical mean temperature of about 28 degrees.