Informal carers' energy bills are on average £176 higher than other bill payers and almost four in 10 struggle to pay them, a survey suggests.
Some 38% of informal carers - those who give regular, ongoing help to another person without payment - have struggled to pay their energy bills in the past and 13% have been pushed into debt by their combined utility bills, the poll for uSwitch found.
Three quarters (73%) said they have had to keep the heating on for longer than usual due to the needs of the person they care for, while they have an average of two pieces of specialist electrical equipment such as stair lifts or electric wheelchairs in their homes.
An estimated 4.9 million people in the UK act as informal carers, Government figures suggest.
However the survey, released to coincide with Carers Week, found that their role requires an average of 10 hours a day, meaning that almost half (45%) find it difficult to work full time.
The survey findings, released to coincide with Carers Week, found 34% have at times chosen not to put the heating on because they could not afford it.
Of those who have struggled with their energy bills, almost half (45%) have dipped into their savings to pay them, used overdrafts (22%) or paid on a credit card (19%).
Almost half (45%) said they received no Government benefits, while 24% receive the Carers Allowance of up to £64.60 a week and 28% receive the Winter Fuel Allowance of between £100 and £300 - available to people aged 65 and over - and 14% receive the £140 Warm Home Discount.
Uswitch is calling for eligible households to be automatically enrolled for the Warm Home Discount rather than having to apply, and for all suppliers to pay it rather than just the largest - allowing vulnerable customers to access the cheapest tariffs without fear of losing financial support.
Claire Osborne, energy spokeswoman at uSwitch.com, said: "The UK's many dedicated carers are at a disadvantage when it comes to their household bills.
"Spending more time at home looking after family or friends, many of whom use specialist equipment to help manage their condition, often means using extra gas and electricity which bumps up energy costs.
"It's vital that we care for our carers. Government proposals to share data to help energy suppliers identify and support vulnerable individuals are a big step forward. But uSwitch is also calling for the support system to be made more effective."
An Ofgem spokeswoman said: "Our rules are clear on suppliers meaningfully engaging with their customers who are struggling to pay bills, to get them onto deals and provide them with support.
"Customers should expect support from their supplier and shouldn't hesitate to contact them if they face financial difficulty in paying their bills."
Opinium surveyed 238 informal carers who live with the person they care for between March 9-15 and 2,001 bill payers who are non carers.