Mountain Fuel Supply Co. ranked among the 25 least-expensive natural gas suppliers in the United States in a recent national study. Unfortunately, that ranking included only the Rock Springs, Wyo., areas served by the company.

For its Utah operations, the company checked in at number 61 of the 212 companies included in the survey. The survey was conducted by the National Association of Regulatory Utility Commissioners in Washington, D.C.Overall, though, the Rocky Mountain area did well, placing nine areas in the least-expensive 25. Only five of those areas, all five in Indiana, were located east of the Mississippi River.

The cheapest natural gas, at 32 cents per therm, was in Amarillo, Texas. The most expensive was in Honolulu at $1.34 cents per therm. The national average was 56 cents.

At 49 cents per therm, the cost for Utah customers was below the national average and only 6 cents higher than the 43 cents being charged Mountain Fuel customers in the Rock Springs area.

Other than Honolulu, only one of the 25 most-expensive locations was west of the Mississippi River and that was, ironically, in Lockhart, Texas, at 75 cents per therm.

Eighteen of the most-expensive locations were in the gas-starved Northeast, including eight in Massachusetts, three each in New York and Connecticut, two in New Hampshire and one each in Pennsylvania and New Jersey.

Colorado placed four areas in the least-expensive group, along with three from Wyoming and one each from Idaho and Montana.

The study was based on average residential billings in January, February and December of 1990.

The residential cost was only 2 percent higher than in 1989 despite a 4.6 percent increase in the consumer price index.

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(Additional information)

Natural gas rates

Location Cost per therm

Most expensive

Honolulu, Hawaii $1.34

Barnstable, Mass. .98

Springfield, Mass. .92

Haverhill, Mass. .87

Hartford, Conn. .85

Least expensive

Amarillo, Texas .32

Fort Smith, Ark. .33

Cheyenne, Wyo. .35

Winchester, Ind. .35

Castle Rock, Col. .35

Colby, Kan. .35

National average .56

Salt Lake City .49