(Wyoming News Service) The Wyoming Public Service Commission held its first public comment hearing Monday in Rock Springs on Rocky Mountain Power's proposal to increase rates by more than 20 percent, which would add nearly $17 on average to monthly bills. 

Rob Joyce - energy organizer with the Sierra Club's Wyoming Chapter - said 97 percent of the increase is meant to cover highly volatile Net Power Costs of coal and natural gas, according to testimony in the utility's application.

"Groups like Sierra Club have been saying, 'This is a risky investment. Fuel costs are going to change and likely go up in the future. We should make the transition to renewable energy now,'" said Joyce. "They didn't listen, and now us the ratepayers are kind of on the hook."

Rocky Mountain Power says rate increases are necessary to ensure reliable service even when the costs of fuels needed to heat and cool homes spike. 

The cost of natural gas recently rose by 89 percent. Prices for the globally traded commodity can be volatile because of extreme weather, international events and other factors the utility says are beyond its control.

Joyce said unlike fossil fuels, wind and sunlight are free. They are just as good at producing power to heat and cool homes, and are not vulnerable to shifts in global markets. 

He added that there are also health costs associated with continued investments in burning fossil fuels.

"Every year that coal plants are kept online," said Joyce, "that elevates these health impacts like increased asthma attacks, bronchitis - and in severe cases, heart attacks and death."

The rate increase is expected to collect an additional $140 million per year from customers. 

Advocates for seniors living on fixed incomes have warned that if the commission approves the increase, people will have to choose between heating or cooling their homes and paying for medicines. 

But Joyce said that financial risk is not shared by Rocky Mountain Power's shareholders.

"Baked into their agreement, since they are a monopoly, they are guaranteed a rate of return," said Joyce. "They are guaranteed that they are going to make money off of their investments, no matter what happens."