Two groups have crunched the numbers and reveal new transmission line construction could cost all Albertans between $150 and $400 extra per year on their power bills.

During a news conference Monday, NDP Leader Brian Mason released an October 26 letter to the PC Caucus from Alberta Direct Connect and the Industrial Power Consumers Association of Alberta, which detailed concerns of how much new transmission lines will cost every Albertan.

"There is cost escalation that has not been taken into account," said Mason.

The letter, co-authored by Colette Chekerda with Alberta Direct Connect, was sent to caution the government that rate increases could be too high.

"There are definitely elements of the transmission plan that we question," said Chekerda.

The information shows an average household paying about $15 a month for power now, but by 2018, it will be edging closer to $50 a month.

"We are building transmission infrastructure that will last Albertans for decades. We don't think it's appropriate that today's consumers bare the burden," said Chekerda.

The energy minister says the line proposals are before a utility commission hearing to determine their need and cost.

"For every billion dollars of construction it will be one dollar on the residential bill now," said Ron Liepert.

"Well at $15 billion, which is the latest update on the transmission plan, times 15 is $15...gets you pretty close to the numbers were are talking about here," said Chekerda.

The groups told CTV News they did not hear back from any government after sending the letter back in October, but they plan to continue to press their concerns at utility hearings.

With files from Kevin Armstrong