Single Australians are spending heavily on their lifestyles and a quarter have run up concerning levels of debt, a new survey says.

The Cost of Being Single report, released by Suncorp Bank, estimated the average single person was spending $335 per week more than people sharing a household or relationship expenses.

Suncorp regional manager Monique Reynolds said an estimated 40 per cent of single Australians lived alone.

"Singles are spending, on average, $335 extra a week; it's all about their lifestyle, weekends away, entertainment ... and their personal grooming," she said.

"It's a bit of a concern when you consider that one in four singles already has a credit card debt of around $10,000."

Ms Reynolds said the bank's message to singles was they needed to draw up a budget, especially when they had sole responsibility for their living costs.

"When we surveyed a lot of the Australian singles, three quarters actually said they don't have a budget and they give little thought to planning ahead, which is concerning when they have that level of debt," she said.

The bank's survey found one in five single people thought they would definitely spend less if they were in a relationship.

Ms Reynolds said the survey found men less likely than women to think about the state of their finances.

"Men are quite blase around their spending habits," she said.

Ageing population, relationship breakdowns drive change

Demographer Bernard Salt said several factors were driving a rise in the number of single households.

"Single person households, by my figures, comprise around 23 per cent of all households in Australia ... but in terms of new households they are comprising up to a third in some areas," he said.

He said the ageing of the population and couples separating later in life were driving single household growth among older age groups.

Bernard Salt said 'singledom' was on the rise in Australia. ( ABC News )

"We are ageing and a lot of the singles in the future will be in their 60s and 70s," he said.

"If you're living as a couple then your electricity costs, for example, don't double, they increase.

"[If] you're putting a load of washing on for one, you might as well do it for two, so there are cost savings simply by living with someone."

Mr Salt said more relationships were now breaking down among people beyond 60, possibly because of the empowerment of women over recent years.

"I think the modern generation of baby boomer women think, 'No, I'd rather be single than be in a relationship that doesn't suit me'," he said.

He said the single pension, understandably, had to be more than half that of a couple's aged pension.

"If you're working with a partner for 30 or 40 years you do have two incomes, or maybe it's one-and-a-half incomes over that time frame if you've raised children, so you've got more pistons driving the economic machine," he said.

"There's no doubt if you are a single, by the time you get into your 50s or 60s there is every chance you are in a lesser [economic] position than those in a coupled relationship."

"We will see the rise of 'singledom' being a major social force in the 2020s," he said.

HECS debt, technology face young singles

As for younger singles, Mr Salt said they faced some expenses that did not exist for past generations.

"During their 20s, most singles don't have kids so they can spend money pretty much as they wish," he said.

"I suppose many parents would like them to be settling down and saving for a house, but many of them choose to travel [or spend on] entertainment, technology, relationships ... and HECS debt.

"There is a range of spending options that 20-somethings have today that pretty well weren't there a generation ago."