Of the 36% of people who said they could not afford their power bills, eight in 10 (80%) cited rising energy costs as a reason, the Citizens Advice Scotland (CAS) survey found.
Meanwhile, almost two thirds (65%) said the rising cost of living was an issue – while 40% said low incomes were an underlying problem.
Just under a quarter (24%) said that their home being hard to heat was a factor.
CAS said it comes as people face a “perfect storm” this winter, with rising energy bills following the increase of the energy price cap, the crisis in the energy market seeing some suppliers go out of business, and the end of the Universal Credit uplift.
It has launched a Big Energy Saving Winter campaign encouraging people to get advice to tackle rising bills.
CAS Fair Markets spokesperson Kate Morrison said: “The fact that one in three people find their energy bills unaffordable is unacceptable, and what this research shows is that the underlying reasons can be varied and complex.”
Pete McGinnie, 45, from Edinburgh, worked in a call centre before having to retire due to ill health.
He is on disability benefits and has often found it difficult to afford the cost of living, particularly the cost of domestic energy bills.
Last year he sought help from his local Citizens Advice Bureau, who told him he could claim the Warm Home Discount, a grant that cuts your fuel bill by £140 per year.
He said: “They told me I was eligible for something called the Warm Home Discount. I had no idea about this, and it was such a weight off my mind. It made a big difference to me.
“I’m still finding it hard at times, but this help meant I was able to heat my home again, and didn’t feel I had to switch the lights off and sit in the dark. I only wish I had asked for their help sooner.”
The survey of 1011 adults was conducted for CAS by YouGov in mid November.