The winter fuel allowance pays £400 for the over-80s
People aged 60 years old or over by Sunday are being urged to claim the full Winter Fuel Payment allowance as soon as possible by Energyhelpline.
The allowance, of at least £250, is made automatically to millions of people who receive a state pension or other social security benefits.
But others may have to apply for the allowance individually, said the consumer switching service.
These may include men aged 60 to 65 who are not eligible for a state pension.
"If you haven't received the payment before, you need to apply," said Mark Todd at Energyhelpline.
The winter fuel allowance pays £250 for the over-60s and £400 for the over-80s.