At a public hearing Wednesday night in Milford, dozens of speakers expressed outrage over soaring utility rates.

Several singled out North American Power, which is one of the suppliers available through the state’s electricity exchange, as the biggest offender.

Other companies also were mentioned. Speakers said their variable rates almost tripled this winter and their utility bills more than doubled. They pleaded with state officials to help them.

Responding to the complaints, North American Power spokeswoman Tiffany Eddy said Friday that the company voluntarily informed its customers in December that rates could substantially increase this winter, and urged them to take a fixed rate. Eddy also said some of the people who complained about North American Power at the Milford hearing were not North American Power customers.

Public Utilities Regulatory Authority officials announced last week they have “opened a docket” to look into complaints from consumers, and scheduled five public hearings around Connecticut to learn about consumers’ experiences with electricity suppliers in the exchange.

Elin Swanson Katz of the Office of Consumer Counsel has said her office has received many complaints about skyrocketing electric rates from people who “felt they were taken advantage of.” Katz pledged that PURA is performing a thorough investigation.

Eddy said company officials anticipated prices would increase substantially this winter because of a lack of available natural gas resources in New England. She said the company emailed and mailed letters to all of its customers on variable rate plans, offering to switch them to a fixed rate.

Eddy provided CT News Junkie with a copy of the correspondence. The letter begins in all caps stating “IMPORTANT NOTICE ABOUT YOUR NORTH AMERICAN POWER ELECTRIC RATE.”

“Because your continued satisfaction is extremely important to us, we want to make you aware of a situation that is going to significantly impact the forecasted cost of electricity within the New England wholesale market this winter,” the letter states.

The letter goes on to state that because of record demand for natural gas this winter, prices are likely to increase.

“This increase will affect the winter electric supply rates of both the utilities and retail suppliers across the region,” North American Power’s letter states. “To minimize the impact to you, North American Power is offering its valued customers the opportunity to lock in on a fixed rate plan that will allow you to stabilize your energy costs and get through the winter with peace of mind knowing your rate is guaranteed not to change for the duration of the term.”

Eddy said the company’s mission is to “always make sure our customers are satisfied.”

“We wanted to protect our customers,” said Eddy, while adding North American Power has 280,000 energy customers, including 60,000 in Connecticut.

She said North American Power offers a Guaranteed Savings Plan, through United Illuminating Co. and Connecticut Light & Power, which is a variable rate plan “that is guaranteed to beat the utility’s rate-to-compare through June 30.

“Customers can leave this plan at any time, with no cancellation fee — so it provides both the stability of a fixed rate plan and the flexibility of a variable plan. In addition to this plan, we offered a fixed rate of 9.49 cents for 10 months. We notify customers in advance when each plan expires,” Eddy said.

During Wednesday’s forum, some speakers alleged that they even had fixed rates that would spike.

But Eddy said customers on a fixed rate plan pay the same price every month for the term of the plan.

“We do not change the rate over the term . . . we notify them in advance that the term is about to end, and that they can either contact us to switch to a new plan or they can do nothing and move to our month-to-month variable plan, per the terms of their original fixed price agreement. It’s important to note that this is not a requirement, and we do so voluntarily,” Eddy said.

A PURA official could not be reached for comment Friday. Commissioner Michael Caron has said utility complaints have more than doubled from a year ago.

State Sen. President Pro Tempore Donald E. Williams Jr., D-Brooklyn, and State House Majority Leader Brendan Sharkey, D-Hamden, have proposed several ways of making the process more transparent.

Williams and Sharkey are seeking to require additional, prominently printed information on electric bills, including notification of rate increases, date of auto-renewal, and any cancellation fees.

The Democratic leaders are seeking to print standard offer rates on every bill next to the applicable private supplier rate, and require online bills to display the same information as required on printed bills.

And lastly, Democrats’ want PURA to establish an online marketplace where customers can easily compare all private electric supplier offers and purchase directly through the marketplace.

PURA has scheduled hearings for Monday 6:30 p.m. in Room 135, Brookfield Town Hall, 100 Pocono Road, Brookfield

Tuesday, 6:30 p.m. in the Norwich City Hall, 100 Broadway, Norwich

Thursday, 6:30 p.m. in the City Hall Building, Veterans Memorial Hall – 2nd Floor, 235 Grand St., Waterbury