Women have bigger carbon footprints than men - because they do most of the energy-hogging housework.

Single, low-income mothers have the least control over their free time and are the most trapped in high-carbon lifestyles, a study of personal carbon dioxide output shows.

By contrast, free-spending, time-rich Dinky couples (double income, no kids yet), are the most likely to be able to lessen their footprints.

A study called Time, Gender and Carbon, co-authored by University of Canterbury political scientist Bronwyn Hayward, has looked at how British adults' use of time outside their jobs affected personal CO 2 output.

At 22 kilograms of CO 2 emitted on an average day, a British woman's carbon footprint is slightly higher than a man's - at 20kg a day - because women spend more time doing non-paid work, eating up the clock with carbon-intensive chores such as cooking, cleaning, shopping and laundry, the study finds.

"These daily chores tend to be women's work - so that high-carbon output simply measures a division of labour in the home," Dr Hayward said.

Men spent more non-work time on leisure, pumping out more CO 2 than women in travel and accessories for sports and recreation.

Dr Hayward suspected the gender variations would be mirrored in New Zealand. However, because New Zealand used more hydro power, rather than the coal and gas used in Britain, it was likely Kiwi women would create fewer household emissions.

That gain could be offset by bigger agricultural emissions and New Zealand's greater reliance on private cars because of its comparative lack of public transport.

Because greenhouse gas emissions were often unavoidably "locked up" in the production and distribution of goods and services, cutting personal output was difficult without government action, Dr Hayward said.

"Reducing our carbon footprint is a lot more complex than just telling people to do the right thing - lots of people want to do the right thing but they physically can't."

However, New Zealanders had a "huge advantage" over the British because they already tended towards "low-carbon leisure" - spending time with family and friends close to home.

The study will be published in the journal Ecological Economics this week.

- © Fairfax NZ News