New research suggests spending money really can make us happier, as long as we're spending it on making more free time for ourselves – by employing a cleaner or paying to get the car washed, for instance.

Perhaps it's a sign of our increasingly hectic lives, but the study found that buying time with our money gives us a better sense of well-being than buying yet more material stuff.

An international team of researchers surveyed 6,271 people across the US, Canada, Denmark and the Netherlands, and found the same link between buying time and life satisfaction irrespective of the overall level of income.

"People who hire a housecleaner or pay the kid next door to mow the lawn might feel like they're being lazy," says lead researcher Ashley Whillans from Harvard Business School. "But our results suggest that buying time has similar benefits for happiness as having more money."

Study participants were asked whether they spent money to buy themselves free time, and if so how much they spent each month. They were also quizzed on how satisfied they were with their lives and how pressed for time they felt.

Across the board, those who spent money to free up time reported greater life satisfaction overall, the researchers report, leading to less time pressure and a better mood.

"The benefits of buying time aren't just for wealthy people," says one of the team, Elizabeth Dunn from the University of British Columbia in Canada. "We thought the effects might only hold up for people with quite a bit of disposable income, but to our surprise, we found the same effects across the income spectrum."

The researchers also conducted a field test, asking 60 adults from Vancouver to spend $40 on a time-saving exercise one weekend, and $40 on a material purchase on another weekend.

Sure enough, people were happier when spending the cash on something that freed up time rather than something material – so maybe you're better spending the money you've saved up for a lawnmower on a gardener instead.

That won't be surprising if you've read up on this before, as previous studies have found more time is likelier to make us happier than more money. Maybe it's a sign of a global society that's getting wealthier and busier at the same time.

We've also seen studies that suggest the happiness we get from spending money depends on our personalities – so there's unlikely to be a one-size-fits-all solution.

This new research also discovered that very few of us make time-saving purchases in our day-to-day lives. Within the sample, 818 millionaires were asked about their spending habits, and almost half of them weren't spending any money on outsourcing time-consuming tasks.

A different set of 98 working adults were asked how they would spend an unexpected windfall of $40, and only 2 percent of the purchases were time-saving ones.

In other words even though delegating tasks and making more time for ourselves is good for our sense of contentment, it's not something we seem all that keen to do.

"Although buying time can serve as a buffer against the time pressures of daily life, few people are doing it even when they can afford it," says Dunn.

One reason could be that paying for a cleaner or to get the shopping delivered makes us feel like we don't have control over our own time, suggest the researchers.

"My take home message is, 'think about it, is there something you hate doing that fills you with dread and could you pay somebody else to do that for you?'," Dunn told Helen Briggs at the BBC.

"If so, then science says that's a pretty good use of money.'"

The research has been published in PNAS.