With more people generating electricity from the sun, Meridian Energy plans to change the way it buys it, retail manager Bill Highet says.
The change will stop the state-owned company losing money on large producers but still pay smaller producers a good price.
For about eight years, Meridian has been buying back electricity produced by individuals at the same rate that it sells it to them - a one-for-one ratio. It's the highest buy-back price of any New Zealand power company, and Meridian gets one or two new customers a day because of it.
When that pricing started, the company had only a handful of home producers. Now the price of solar panels has dropped and there are 650 home generators nationally, with 11 in the wider Whanganui region. More than 90 per cent are generating electricity through photo-voltaic solar panels, with a few others using small wind and hydro systems.
All of Meridian's own power generation is from wind and hydro, and supporting renewable energy is part of its branding. But it is also expected to make a profit. And it doesn't want its ordinary customers to be subsidising electricity for home generators.
"We don't believe it is fair or sustainable to make a loss on one customer group - as we currently do with home generation customers - at the expense of other customers," Mr Highet said.
By the time there were 200 home generators the company was losing "a substantial amount" of money on its buy-back pricing. For one thing, it was reimbursing in total the lines charges that are part of every power bill. For another, it was paying home generators more per unit of energy that it pays for its usual wholesale supply.
Mr Highet said it was now moving to change its pricing. Home producers will be paid 25c to 27c for each kilowatt hour (kWh) they produce, up to 5kWh per day. After that the rate will be closer to 10c a unit - nearer the wholesale price. The lines charge component of the bill will be "unbundled", so that customers rather than Meridian will be paying it.
He wasn't able to say when the changes would happen, but said they would not disadvantage small producers, who are the majority of home generators.
"Even with the changes, it will still be the best [price offered], as far as we know."
Most people with solar panels on their roofs will be unaffected, because they produce little more than they consume.
One of those is Wanganui's Bruce Anderson, an electronics technician on the point of retirement. He's always wanted his own solar array and spent $16,000 on a system of photovoltaic panels. It started producing electricity on December 5.
The average house uses 8000 to 10,000 kWh a year, and he thinks his system will easily supply that. He's noticed that it generates electricity even when it's raining - all it seems to need is daylight.
He's calculating it may only take nine years to pay for itself in saved electricity, and the time could be less if power prices continue to rise. That's a return of 11 per cent on what he spent, a better interest rate than his money would get from a bank.
Mr Anderson isn't the only one making those calculations. Mr Highet said it used to be only clean, green people installing solar electricity generators: "There are a lot more doing it now for personal economy reasons. A lot of them are nearing retirement age."