The systems are expected to generate about 4.2 gigawatt hours of electricity a year, equivalent to the annual power use of more than 500 homes.
Christchurch-based Calder Stewart director Sam Stewart told the Herald that “big sheds” were very much the firm’s bread and butter.
The company often undertakes study tours overseas.
“We saw where things were going in Europe and in California especially,” Stewart said.
“It was like, what do we do now to get ahead of this rooftop solar thing that’s happening everywhere else but in New Zealand.”
The move towards solar started with strengthening buildings to become solar-ready but without necessarily installing it at the time of construction.
The firm then reserved the rights to those roof spaces through an easement structure.
“We did that for a few years before I came back from the UK and said we should do something with this.
Calder Stewart is investing $110 million in rooftop solar.
“It started with retrofits but now it’s every single building as they come through the pipeline,” he said.
The firm is now checking out the battery side of the equation, particularly as battery prices fall.
Initially, solar worked out well for building owners as it would supply power to them during the day, helping to avoid the morning and evening demand peaks.
Now the firm is eyeing batteries.
“It’s probably not something that makes absolute commercial sense now, but we are planning for the future,” Stewart said.
“It’s something that we need to understand a bit more.”
Calder Stewart has completed a distribution centre for Fonterra in Christchurch, a facility for Briscoe Group at Drury in Auckland and another one for NZ SafetyBlackwoods on the same site.
In general, the price per kilowatt installed is coming down, and that’s a multi-year trend, Stewart said.
Calder Stewart’s first solar installation provided 50 kilowatts (kW).
Now, the firm will not do anything under 100kW and often 500kW plus.
Stewart said adoption of rooftop solar across the country’s industrial sites could save millions of dollars in transmission and distribution-related costs, while reducing the need for additional grid investment.
He says network losses typically add around 5% to 10% to the amount of electricity users pay for, meaning industrial businesses are effectively paying for more power than they consume onsite.
Ben Krieble, Calder Stewart’s energy manager, says the company’s model allows tenants to access cheaper solar power without needing to fund or own the solar infrastructure themselves.
Because the generation is on the roof, there are no lines charges, no network transmission losses and no levies attached to that portion of the electricity.
“That allows us to undercut the normal retail power cost because we are generating the power where it is being used,” he said.
The planned battery rollout would allow more solar power to be used onsite and help reduce demand from the grid during morning and evening peaks.
Data from the Ministry of Business, Innovation & Employment (MBIE) showed renewables generated 94.5% of all electricity in the March quarter, up from 83.2% in the same quarter last year.
A favourable mix of strong hydro inflows, increased wind output, and a 50% year-on-year increase in solar generation helped keep renewable electricity generation high in the quarter.
Record solar generation of 373GWh reflected rapid growth in new capacity, including large-scale solar farms such as Pāmu Rā ki Whitianga, and Te Herenga o Te Rā near Ōpōtiki, alongside strong summer solar conditions, MBIE said.
Jamie Gray is an Auckland-based journalist, covering the financial markets, the primary sector and energy. He joined the Herald in 2011.
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