SALEM — Oregon’s natural gas companies say customers will see double-digit reductions in their heating bills this fall and winter, mainly as a result of a struggling economy that has lessened demand for gas.

At a briefing Tuesday, the three companies supplying Oregon consumers told state regulators that prices could be as much as 10 to 20 percent lower when customer rates are revised.

The companies’ new rates are expected to be filed with the Oregon Public Utility Commission in late August and take effect in November.

A year ago, before the global financial meltdown, the companies were warning of possible double-digit price increases.

Now, the Public Utility Commission says the “crater” the economy has fallen into and large natural gas inventories will bring about big reductions for customers of NW Natural, Avista Utilities and Cascade Natural Gas.

“The economy has really put a dent in demand for gas,” said PUC Chairman Lee Beyer. “The lower prices should help many cash-strapped households this coming winter.”

Randy Friedman of NW Natural, Oregon’s largest gas utility, said residential and commercial customers alike are using less gas as businesses curtail operations and homeowners tighten their belts by being more energy efficient.

“It looks like 2009 is going to be the first time in 50 years that natural gas demand is going to be lower than the previous year,” Friedman said.

Also contributing to large inventories of natural gas, he said, is improved technology companies are using to extract natural gas from shale.

Officials said “wild cards’ that could change that trend include the hurricane season, gas pipeline disruptions or unforeseen reductions in supplies. Oregon’s natural gas is imported through pipelines from Canada and the Rocky Mountain region.

More than 715,000 Oregonians receive natural gas from NW Natural, Avista Utilities or Cascade Natural Gas.