Campaigners against fuel poverty have called on energy companies to do all they can to help vulnerable customers.
Energy Action Scotland made the plea as the latest price hikes for gas and electricity came into effect.
Power firm E.ON announced last month that dual fuel customers will see their bills rise by an average of 8.7%. The average increase for gas-only customers will be higher at 9.4%, with an average increase of 7.7% for electricity-only customers.
Energy Action Scotland director Norman Kerr said: "Although they are the last of the big six companies to increase their prices, E.ON's move will still hit customers already struggling to afford to keep warm at home this winter.
"We know that many people such as the elderly, those with young children, people with a disability and others on low incomes fear their fuel bills and often ration their use of gas or electricity, perhaps to the detriment of their health.
"The energy companies must do all they can to provide support for customers who are low income or vulnerable. It is also essential that people take up the help that is on offer."
When the price rises were announced in December, E.ON chief executive Tony Cocker said the firm has held back from increasing bills for as long as it possibly could, adding that at the same time it had worked hard to reduce its own costs.
But he stated: "Some 16 months after our last price increase, and almost a year since we actually cut our electricity prices, we have had to make the difficult decision to increase our prices."
Mr Cocker said the price E.ON paid for energy on the national and global wholesale markets had risen.
He added that another reason for the increase was the power company was having to pay more in network costs to other firms, to cover the cost of transporting gas and electricity to customers' homes.