The Government Boiler Scrappage scheme has issued 54,758 vouchers since the scheme was launched in January.
There are still around 70,000 vouchers worth a total of £28 million available.
The scheme was launched to upgrade up to 125,000 household heating systems in England to cut carbon, save money on fuel bills and sustain work for the heating industry.
All the major energy companies which sell and install boilers, including British Gas and E.On, have now matched the offer, giving householders potentially £800 off the cost of a new efficient boiler.
The Energy Saving Trust is receiving 5,000 enquiries on average per day to its 14 call centres across England.
Energy and Climate Change Secretary Ed Miliband said: "The scheme is helping householders to save around £200 a year off fuel bills and reduce emissions while helping to sustain work for the 130,000 installers and up to 25 sUK-based boiler manufacturers throughout the economic recovery."
Energy Saving Trust