Fewer than 60 homeowners have availed of sustainable energy scheme grants

However, some 700,000 homes are heated by traditional coal, peat, oil and gas systems and climate action agreements point to all of them having to switch to more efficient methods if carbon reduction targets are to be met.

Tom Halpin, head of communications with the Sustainable Energy Authority of Ireland (SEAI) which has operated the Government funded scheme since it began in April, said 370 grants were offered up to Christmas, of which 56 have been claimed.

But he emphasised that there is a lead-in time for homeowners hoping to avail of the grant as they have to first have their home assessed as ready for heat pump installation.

Houses with poor insulation need to have that remedied first and the SEAI has warned that houses more than 30 years old may need costly upgrades. However, Mr Halpin said: "The rate of applications is steadily increasing."

He said he is not aware of any difficulties in getting assessments carried out despite anecdotal evidence of delays in some areas. There are 124 SEAI approved technical advisors available to do assessments around the country, details of whom were on the authority website, he said.

The grant is worth €3,500 although in some cases the job may cost multiples of that depending on the type of unit bought, the size of the house and scale of the installation task.

A further €200 grant towards the technical assessment is also available and the grants for external wall insulation have been increased to between €2,750 to €6,000.

Irish households have the highest carbon emissions in Europe. Energy-related carbon emissions account for about 60% of the country's total carbon emissions and about 25% of that comes from the residential sector.

Two other new clean energy grants introduced this year have had a greater take-up. Mr Halpin said 1,939 electric vehicle grants, worth up to €5000 each, and 957 home charger grants, worth up to €600, had been paid out to the end of November.