According to the Sun, the Post office has been issuing these vouchers on behalf of British Gas, E.ON Next, Ovo Energy, EDF Energy, Scottish Power, and Good Energy since October 21.
This scheme - which is delivered by the Department for Energy and Net Zero - gives households claiming certain government benefits a £150 discount on their electricity bills between October and March each year.
190,000 households could miss out on free £150 if they don't respond to letter Over 190,000 Brits could miss out on a free £150 discount on their energy bills this winter.
Kevin Elson, postmaster at Bache Post Office, told the paper: "We know many people are worried about the cost of their energy bills as the colder weather starts to set in.
However, households with older, traditional prepayment meters that require a key or card for top-ups cannot receive the discount directly.
