The sold-out audience which filled Auckland's Q Theatre erupted into laughter when the evening's host Samantha Hayes asked when National would be "rolling out" the flock.
Mr Groser also highlighted "the disaster that is climate change policy" in Australia as a warning for what could happen when parties didn't compromise on the issue.
Greens leader Dr Russel Norman unsurprisingly received the warmest welcome at the debate and described climate change as "the biggest threat facing the planet, but also the biggest opportunity".
He highlighted green economic opportunities had the support of Conservative parties overseas.
"The clean energy finance corporation in Australia has made lots of money by investing in clean energy."
Internet Mana candidate John Minto described climate change as "the great moral issue of our time".
New Zealand was "the mouse that roared" with its nuclear-free stance, and the country should take a stand again to prevent a "global catastrophe", Mr Minto said.
He conceded there would be those who would "never want to get on a bus or a train" but said that by improving public transport they would be able to drive on a gridlock-free road, negating the need for more motorways.
Labour party deputy leader David Parker said Labour favoured reviewing the Emissions Trading Scheme to include agriculture, rather than scrapping it and replacing it with a carbon tax system ? as was the Greens policy.
He added that the parties' differing stance on the policy was not a coalition deal-breaker, and they would work on a solution post-election.
NZ First deputy leader Tracey Martin said climate change was an issue wider than Auckland and public transport.
She also described the Emissions Trading Scheme as a failure, but said it was a problem that needed a cross-party solution, as opposed to adopting one party's policy. "Let's have a chat about it later on shall we...? The water's rising, let's just come up with solutions."
Maori party candidate Nancy Tuaine also spoke and said the country had sold a '100 per cent pure' brand world-wide, but hadn't been prepared to stick to it.
The Conservative Party didn't respond to its invitation, Hayes said.