The YouGov Reports poll found that of those spending 10% or more, 68% had turned the heating down or off when they ordinarily would have left it on, 27% had spent less on food and 5% had borrowed from short-term lenders to manage bills.
Some 44% of those not in this group said they had had to reduce their usage.
The poll also revealed negative opinions about energy suppliers and prices, with 84% agreeing that companies were quick to raise prices when their costs went up but slower to offer discounts when they fell.
More than two-thirds (67%) agreed that big energy suppliers acted as a "cartel", while 66% said the electricity and gas supply market had major problems the government needed to address.
Half of those polled (50%) believed UK household energy bills were some of the highest in Europe, while 9% said big suppliers treated their customers fairly.
More than two-thirds (69%) favoured forcing suppliers to simplify bills.
YouGov Reports UK research manager Tom Rees said: "Our research indicates how little consumers trust energy suppliers, the high level of dissatisfaction with the energy market and the tangible effect on household finances."
YouGov commissioned two surveys, of 2,079 and 2,113 UK adults.