CALGARY - Energy bills arriving in Fort McMurray, Alta., months after a wildfire forced the entire city to evacuate have come as a shock to some residents still trying to restore some normalcy to their lives.

Many have taken to a Facebook support group to vent their frustration at recent bills that lumped together months' worth of charges, in many instances demanding four-digit sums at once.

Carla Young said she can't fathom how her bill came to more $1,700 and has been struggling to get an explanation from her provider, Direct Energy.

"I was not impressed at all," said the mother of three, who runs a swim team.

When she got someone from the company on the phone, she said "they didn't understand it either."

The city was emptied out for most of May while firefighters battled the blaze and crews worked to get basic services back up and running. People were allowed to return in phases beginning in early June.

A Direct Energy bill of more than $1,100 was an unwelcome surprise for massage therapist Christine Unruh, who returned to her house in mid June to find it damaged by water.

Unruh's bill includes charges spanning early April to early August.

She couldn't figure out how the company came up with its final tally. The bill shows higher electricity usage for the month of May - when she was out of her home - than it did for April.

But the sum includes credits to offset amounts charged between May 4 and June 4, including $85 for electricity usage and about $170 for distribution fees.

Even with the credits, the bill is a lot for her family of four to handle at once and some leniency from the company would have been welcome, she said.

"When I called them, the lady on the other line couldn't care less about my problem," she said.

"This is the first time we've had issues with Direct Energy or their billing process, but we're definitely exploring other options and have been in contact with some of their competitors."

Martha Boyko, an educational assistant at a high school, said she was taken aback when she and her husband got a nearly $700 bill.

"They just said that's the way it is and that's what you have to pay," she said.

Her husband, who works in the oilsands, has had his hours and pay cut back, so money was already tighter.

"There's only so many punches you can take."

Direct Energy has 26,700 customers in Fort McMurray and the surrounding area.

Spokeswoman Wendy Tynan said there should be no charges for the evacuation period. It took time to individually apply all of the credits, which is why customers did not get bills for much of the summer.

She said she can see how it would be hard to make sense of the calculations.

"If you're actually going through your bill and trying to analyze it, it's obviously confusing."

A message on the bills informed Fort McMurray customers of the one-time evacuation credits. But the company on Thursday added a more detailed question-and-answer section to its website to help better explain the bills' breakdown.

"This really should be the last thing that you need to worry about," said Tynan, adding customers can call the company to work out payment plans if they're feeling pinched.

"We didn't need to make things harder. We can always do a better job of communicating with our customers."