When New Zealand's largest solar power supply company turned off the lights last month, even its own chief executive was shocked. But as details emerge, the truth behind SolarZero's downfall appears murky.

When the world's largest investor bought out SolarZero, and other global financiers came on board alongside a government green bank to help it grow, its future seemed very secure.

But two weeks ago, the New Zealand start-up was put into liquidation by its directors and staff were given the shock news to leave immediately.

Now under scrutiny by the Finance Minister is the government's Green Investment Finance (NZGIF) which has poured $150 million in taxpayer funds into the kit, including solar panels and batteries installed in customers' homes, free of charge, under a monthly subscription model.

"I don't see that that money's going to come back to the government," says Newsroom Pro managing editor Jonathan Milne.

SolarZero was founded in the 1970s as Thermocell, a solar water heating company, but it evolved to become the country's first solar subscription service.

Chief executive Matt Ward told The Detail in May that its subscriptions were increasing by 50 percent each year, with customers attracted by the prospect of saving hundreds of dollars each year without paying a dollar.

At the time he said the model of SolarZero owning the kit, maintaining it and changing the battery "almost sounds too good to be true. But it is a business model that has been employed through Scandanavia and round the world, because it has the consumer at the heart of it".