More than half the houses which have had insulation installed under the new government subsidy belong to lower income households, the Government says.
The $323 million scheme provides up to $1300 towards the cost of home insulation, typically accounting for between a quarter and a third of the overall cost.
An online survey, commissioned by the Business Council for Sustainable Development, has found people with high incomes are the most likely to warm up their homes using the grant.
The poll of 1578 people shows nearly half of those with annual incomes exceeding $200,000 said they would apply.
This compares to 13% of those earning between $50,000 and $70,000 a year.
The council's chief executive, Peter Neilsen, says a loan system could be better, as while most people could repay a loan, those on lower incomes will struggle to find the shortfall between the cost of insulation and the partial grant.
However, Energy Minister Gerry Brownlee says of the more than 8,000 houses insulated under the two-month old scheme, 57% involved low income households.
Third party funding means many of those on lower incomes will have paid nothing for the insulation, he says.
Mr Brownlee says the revised Emissions Trading Scheme may result in an expanded home insulation subsidy.