The co-leader is not your stereotypical sandal-wearing, muesli-munching greenie - but he says that's an outworn stereotype and wouldn't fit most of the 30 per cent of Green voters in Wellington Central either.
"I would say that I probably represent the average Green Party supporter."
He was a "general-purpose environmentalist" until 1998, when he read an insurance industry report predicting the industry would collapse by 2050 under the weight of climate change-related claims. The report diverted his attention from smaller issues like biodiversity and species extinction to a looming crisis.
He's spent the past years working for big business - accountancy firm PricewaterhouseCoopers, Cadbury Schweppes and the HSBC Bank. In all those businesses, he was steering the leaders toward sustainable development.
HSBC Bank deals with people in Latin America and Asia, where climate change and inequality are impacting. Leaders there were surprisingly receptive.
"This massive capitalist beast was actually quite concerned about some of the big trends around environment and society that I'm concerned about."
Back in New Zealand after 13 years, Mr Shaw said the country was missing out on opportunities to export high-tech, high-value, low-carbon products. He has examples of international and local companies doing well on them.
Government's decision to sell 45per cent of Kiwibank to ACC and the Super Fund has got him steamed up. He says it's a terrible deal for average Kiwis and may end in the bank being partially privatised or a future government being forced to buy back the shares at an inflated price.
Green policy would be to give Kiwibank $100 million, without expecting higher-than-normal dividends from it. The capital would allow the bank to grow and compete on interest rates with the four big Australian banks operating here.
They do 87 per cent of New Zealand's banking and take $4.5-5billion of profit out of the country, he said, the single biggest contributor to our balance of payments deficit.
After the 2017 election, Mr Shaw would like the Greens to be a big part of a new government, with Labour its likely partner.
He said the National-led government was still polling well but had run out of ideas. A fourth term for it would be a first under MMP.
"It's got a one-seat majority. It can't even pass some laws now. The election will be really tight."
He's liking the way new Labour leader Andrew Little is methodically clearing up overdue issues but less keen on his move to scrap a capital gains tax.
"My reading of the public is that it has now largely bought into the idea."
But he said Labour did intend to review the tax system, and he likes its "big thinking" on the future of work.