EUGENE (AP) - Natural gas prices in Western Oregon and southwest Washington are expected to remain generally stable at least for the next year, NW Natural says.

The company serves about 560,000 residential, commercial and industrial customers in the region.

Rates went up 2.6 percent in September and, for residential customers, 3.5 percent in October.

The Portland-based utility has locked in wholesale prices for more than 90 percent of the gas it expects to buy through next October, said Randy Friedman, the company's gas supply manager.

In 2004, NW Natural plans increases totaling 1.75 percent, to pay for pipeline construction projects in Coos County and the Portland area.

The estimated monthly bill for the average residential customer using 62 therms a month will go up $4.22, to $63.17.

The rates are locked in until next Oct. 1 and probably won't increase heading into next winter, Friedman said.

The wholesale gas market has been volatile for more than three years. Prices have fluctuated wildly and are about twice what they were for most of the 1990s.

Prices have come down about 25 percent since last spring, when gas storage hit historic lows.

Supplies rebounded thanks to a cool summer, which kept use of air conditioning low in Southern states and eased pressure on natural gas-fired electric plants.

"We're actually right now at all-time high levels for natural gas storage," Friedman said.

If the economy were to roar back in the next year, it could add pressure on gas prices, which may be felt the following year by residential users, utility officials said.

By buying supplies far in advance, NW Natural has given itself a cushion against short-term price spikes.

"We hedge a year at a time, so we avoid the gyrations that happen day to day or week to week," Friedman said. "But we are not insulated from what's going on in the general market. We'll catch up to it within a year."

The company gets 80 percent of its gas from British Columbia and Alberta. The rest comes from the Rocky Mountain states.