Some of the finance for the first year of the subsidised insulation scheme could run out by Christmas, meaning some homeowners may have to wait until July for the next round of funding.
In May, the Government allocated more than $323 million over four years for the subsidies to retrofit insulation in 180,000 homes.
A target of 27,500 homes was set for the first year of the scheme to June 2010. By the end of September this year, 12,500 houses had been insulated.
The first-year target was divided between 60 service providers, and one of them, Cozy Cool Limited, says its allocation will be gone by Christmas.
The Energy Efficiency and Conservation Authority says because of high demand service providers are retrofitting homes faster than expected.
A spokesperson for Energy Minister Gerry Brownlee says the Government is considering making more money available.