Some people in Airdrie, Alta., aren't happy with 24-hour gas stations hiking prices by 10 cents or more overnight, only to return to normal levels once the morning rush is over the next day.

They say that not long after competitors close for the night, the Shell and Petro-Canada stations along Edmonton Trail in Airdrie hike their prices, forcing people who need it to buy gas at higher prices.

"They shouldn't be able to raise the price just because we don't have any other options," said Matthew Huntley, who works shifts and sometimes has no choice but to use stations open late at night.

"Keeping it for the morning rush and then putting the price back down when everyone's gone to work, it just seems a little unethical and wrong," said Huntley.

Huntley monitored prices for regular grade gas at the 24-hour Shell and Petro-Canada stations, Dec. 3-11, and claims both posted the exact same prices, from a high of $1.08 per litre overnight to a low of 97 cents the next morning. He says others have noticed the trend.

Overnight price hikes for gas are raising questions in Airdrie, a community of 61,000 residents just north of Calgary. (Graham Hughes/The Canadian Press)

The timeline for an Airdrie Facebook group contains dozens of posts from unhappy residents who are spotting the price change and aren't happy with what they call "gouging," with some sharing price updates and photos.

"Shell told me they would talk to the franchise owners but I never heard back from them." Huntley said.

Huntley says he has filed a complaint with Canada's Competition Bureau, asking them to look into the practice.

In a statement, the Bureau told CBC News: "Charging high prices is not illegal in itself; however, it is illegal if competitors have conspired to set those prices. We invite anyone who believes they have evidence of price-fixing to bring it to the Bureau's attention."

Meanwhile, one gas expert says while it might not be ethical or good for consumers, the practice of making overnight price hikes is legal and competitors are free to match each other's prices — which sometimes happens several times a day when prices fluctuate — and doesn't equate to price fixing.

This 24-hour Petro-Canada station on Edmonton Trail in Airdrie has been hiking its fuel prices at night when there's less competition. (Google Street View)

"This is retailers playing with their 12-cent retail margins, and that's causing a lot of frustration not just in Alberta but across the country," said Dan McTeague with Canadian fuel price website GasBuddy.

"Everywhere you go, people want to know why things can springboard back and forth with little regard to what's happening in the market," said McTeague.

McTeague says he's been hearing similar complaints about prices in other Alberta towns and cities, including Okotoks and Brooks.

Eastern provinces like Newfoundland, Prince Edward Island, New Brunswick, Nova Scotia and Quebec all regulate gas sales, which isn't the case in Alberta.

A private member's bill is being proposed in Ontario to regulate gas prices there, controlling retail and price and wholesale mark-up.

"Provincial regulation just papers over the problem," said McTeague. "What we need here is more transparency."

McTeague adds gas retailers have been struggling for a long time in Canada, on some days selling gas for below cost and hoping to make up the loss through their retail stores.

Some residents in Airdrie say they'll boycott the gas stations involved until they see a change.

CBC News contacted both Shell and Suncor, which owns Petro-Canada gas stations, for comment.

In a statement, Suncor said: "Petro-Canada makes independent posted pricing decisions based on a number of factors including market dynamics and site dynamics."

Shell issued a brief statement, saying "local market conditions can affect the day-to-day pricing of fuel as retailers compete for customers."