David Cameron said his plans could "make life better"
Tory plans for energy efficiency grants for more than three million homes would be piloted by 14 English councils and London's mayor, David Cameron says.
The party leader told the BBC the green message had to sound less "miserable", in an effort not to "depress" people.
The Tories say the grants would be worth up to £6,500 per home, with the standard upgrade worth about £1,500.
Households would repay costs via energy bills over 25 years. Labour said the plan was "unfunded" and a "green con".
The 14 councils selected by the Tories are: Broadland, East Sussex, Hammersmith and Fulham, Hyndburn, Kensington and Chelsea, Kent, Lancashire, Leicestershire, Norfolk, North Tyneside, South Holland, Suffolk, Westminster and West Sussex.
Retailers like Marks and Spencer, Tesco and energy companies will also be expected to deliver the scheme, Mr Cameron will announce later.
Details of the proposals come as 192 countries try to agree a new global treaty on climate change at Copenhagen.
Mr Cameron told the BBC: "I think it's important that we don't depress ourselves.
"If we make the answer to climate change sound like sitting in a dark room with a big woolly pullover on, with the heating turned down, with our teeth chattering and being miserable, then we're never going to sell it to anybody.
"We've got to explain that a lot of the things we can do will actually be good for us and good for our economy and cut our bills and make life actually better to live."
The scheme to finance energy improvements like insulation, draught proofing and heating controls was first announced by the Conservatives in January.
The party said energy companies would borrow money, underwritten by the government, to fit homes with measures determined by an independent assessor.
Householders would then repay the money over up to 25 years through their fuel bills, but the Conservatives say they would still save money because bills would be substantially lower.
A standard energy efficiency package would cost about £1,500, say the Tories, but "harder-to-treat homes" would be eligible for grants of up to £6,500.
The party says the standard insulation package would save households £360 a year on heating bills - of which they would keep £240, and pay £120 towards whoever provided the upfront investment for insulation.
The Tories claim the scheme would dramatically reduce carbon emissions, create thousands of jobs in installing and surveying properties among others and will save people money.
In the pre-Budget report last week Chancellor Alistair Darling announced plans to pay people £400 to replace old boilers with new ones, which, he said, would help up to 125,000 homes.
The government's own Warm Front scheme provides a grant up to £3,500 - in some cases £6,000 - for insulation and modernising heating systems, for the over-60s and families with children under 16 if they are on means-tested benefits.
Discussing the Tory plans, a Labour spokesperson said: "This is a green con. At the same time as saying they will cut the deficit, the Tories are making yet more unfunded commitments with no idea how they would find the billions their proposals would cost."