Solar savings not clear cut
Mike Rattray is looking forward to his next power bill after just installing solar panels on his roof.
The Rattrays are part of a growing number of people installing solar panels to save on bills.
On Sunday, the Green Party launched a policy to provide loans to help households switch to solar power, but energy experts say whether it is cost-effective comes down to individual households' power use.
Rattray and his wife, Jayne, had an array of 12 solar panels installed on their Rangiora house last month.
Rattray was not yet able to go over the "facts and figures" of how the new panels would change their electricity bill, because they were still awaiting the meter that would allow the household to export power to the national grid. He has been monitoring the general electricity meter and said for the past few days it had barely budged.
Because there is no affordable way to store the power generated by household solar panels, any excess power goes to the grid and households are paid back by the power company. For many households, power would be generated during the day when no-one is home to utilise it.
The Rattrays have already begun adjusting their lifestyle to maximise the sun-generated power, including cooking dinner earlier.
"I probably think about it more than Jayne does," Rattray said. He tells her to look out the window, and "if it's sunny, go for your life".
The company that installed the panels, at a cost of $10,600, predict the couple will pay it off in seven years.
With days where the panels have been generating up to 21 kilowatt hours, Rattray is anticipating the savings.
"I'm looking forward to the next power bill - not many people can say that."
But where the Rattrays have forged ahead with the upfront costs, Cathy Baker and husband Ken spent 18 months churning figures and could not find a way to justify installation costs for solar panels.
The couple are rebuilding their New Brighton home and had always thought they would move to solar power, so Baker said they were disappointed they could not find a way to make the numbers work.
"It's a big investment for a start, and it's going to take an awfully long time to try to recoup $10,000," she said.
"We couldn't work out any positives for it at all, except that it's a lovely idea."
University of Canterbury engineering lecturer Dr Alan Wood said there were 1250 New Zealand households with solar panels installed, with predictions this would increase to 30,000 by late 2018.
Whether there was a benefit in cost-savings to the consumer depended on how they used the solar-generated power, Wood said.
"Early adopters should be people that consume electricity during the day.
"For them it does stack up but only just."
Wood thought the Green Party's predicted savings to households of $100 a year were over-estimated.
"They have assumed you use all the power yourself, which is not the case."