Key Points:

Green Party co-leader Jeanette Fitzsimons is confident more people will take up a $500 solar hot water subsidy, despite no one taking it up in the past year.

It has been revealed that last year no one took up the subsidy, which was one of the policy concessions the Greens wrung from the Government as part of their post-election deal to abstain on confidence and supply votes in Parliament.

But Ms Fitzsimons today said she was confident a lot more homeowners would take up the subsidy this year.

The number of solar hot water heaters being installed was growing and about 15 building firms had signed up with a commitment to install solar hot water heaters in the new homes they would build.

Ms Fitzsimons said there had been a lot of issues to sort out in what was still a fledgling industry.

Issues included poor quality installation, untrained installers and problems with building consents.

"We've made major progress with that. We have now have a quality standard that they have to meet," she said today on Radio New Zealand.

"We now have performance testing ... to see how much energy each system will save over its life. We have training courses in all the polytechs now and we've subsidised 165 plumbers to do training."

Ms Fitzsimons said plumbers were the only tradesmen allowed to install the heaters, but previously plumbing training had not included solar heating.

A new compliance regime under the building code had also been developed to cut red tape around building consents.

She said four councils were now giving free consents and the average cost at others was about $200.