Efforts to get households to reduce energy use are being hampered by the appliance and gadget-packed homes of single men, research suggests.
Larger households are said to use less energy per capita
Sole occupancy households in England and Wales are said to use the most space and power per capita - with males aged 35-45 the worst offenders.
The rising number of one-person homes also produce more rubbish, University College London researchers found.
Collective housing and eco-friendly homes were cited as possible solutions.
"Previously, the typical one-person householder was the widow, often on a tight budget and thrifty," said Dr Jo Williams, of UCL's Bartlett School of Planning.
"The rise in younger, wealthier one-person households is having an increasingly serious impact on the environment."
Experts have predicted single people will make up 38% of all households by 2026, up from 18% in 1971.
According to a report published in the journal Environment, Development and Sustainability, unmarried men in the 35-44 age group consume 13% more energy and use about 6% more space than one person householders aged over 60.
But the researchers reckon that with the right advertising, such individuals may be willing to invest in more environmentally friendly homes and products in future.
The report also suggests the government could encourage people to live more space-efficiently with the introduction of an occupancy tax.