Rooftop Solar New Zealand Investment Targets Industrial Energy Costs

Calder Stewart has more than 900 hectares of zoned industrial land across Auckland, Canterbury, Otago and Southland, giving the company a large platform for distributed energy generation. Its energy arm, Calder Stewart Energy, has already installed solar systems across 17 industrial sites, covering more than 152,000m2 of roof space and capable of generating up to 3.6MW at peak output.

Those systems are expected to generate about 4.2GWh of electricity each year, which is equivalent to the annual power use of more than 500 homes.

For industrial businesses, the wider significance is not just environmental. Energy is a core operating cost for manufacturers, logistics firms and other high-use industrial occupiers. By generating power on the same site where it is used, rooftop solar can reduce the amount of electricity drawn through transmission and distribution networks.

According to the Energy Efficiency and Conservation Authority, commercial solar investment can help New Zealand businesses reduce energy costs, strengthen resilience and build long-term energy security. More information is available from EECA’s commercial-scale solar guidance.

Why Industrial Rooftops Are Becoming Energy Assets

Sam Stewart, Calder Stewart director, says sector-wide adoption of rooftop solar across New Zealand industrial sites could save millions of dollars in avoided 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.

“If your meter says you have used 100 kilowatt hours, you may actually pay for 105 because of the losses across the network.

“By generating power above where it is used, we can take pressure off the lines network and reduce the cost of moving electricity across the system,” he says.

Stewart says solar will now be integrated as standard into the company’s new industrial developments, while the bulk of existing buildings are expected to be retrofitted within the next 12 months.

He says reducing the delivered cost of power could help lower the cost of producing goods for local and export markets, particularly for manufacturers, logistics firms and other energy-intensive occupiers.

“Every percentage point matters when businesses are operating in competitive markets,” Stewart says.

“If we can help reduce one of the core operating costs for industrial occupiers, that ultimately supports lower-cost production, stronger margins and a more competitive export sector.”

Rooftop Solar New Zealand Rollout Avoids Land-Use Pressure

Stewart says industrial roofs have historically been an underused asset, despite their scale and proximity to large power users. The company’s approach also avoids some of the land-use tension associated with large-scale solar farms by using existing built space rather than productive or developable land.

“We build these buildings and the roof is sitting there unused. The opportunity is to turn that into a productive asset that supports the tenant, supports the grid and creates a long-term return,” he says.

“Our model also avoids some of the land-use tensions associated with large-scale ground-mounted solar by using industrial roof space that would otherwise sit idle.”

Lower-Cost Solar Power Without Tenants Funding the Infrastructure

Ben Krieble, Calder Stewart Energy manager, says the company’s model gives tenants access to cheaper solar power without requiring them to fund or own the infrastructure themselves.

Tenants continue to buy electricity from their normal supplier, but a portion of their power comes from the rooftop solar system at a lower cost.

“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.”

Krieble says some tenants are being offered power price arrangements of up to 12 years, creating greater certainty for businesses planning around energy-intensive operations.

“It is like fixing a mortgage for a longer term. On the backdrop of rising electricity prices and lines charges, fixing that operational cost line gives businesses more certainty as they plan ahead.”

Battery Storage Could Turn Industrial Sites Into a Virtual Power Plant

Battery storage is the next phase of the programme. Batteries would allow more solar power generated during the day to be stored and used when demand is higher, including morning and evening peak periods.

Stewart says batteries could also support wider energy resilience by reducing pressure on local lines networks during periods of high demand.

“The two peak periods in New Zealand are first thing in the morning and around six o’clock at night. If power has been stored onsite, or batteries have been topped up overnight when electricity is cheaper, that power can be used instead of drawing from the grid at peak times,” he says.

“That has benefits beyond the individual occupier. It helps reduce stress on the national grid and local networks.”

Krieble says once battery storage is added at scale, the company’s rooftop solar network could become a form of virtual power plant.

“When you have distributed generation and batteries across a portfolio, it is not just a generation asset. It can provide services to the network, reduce demand when the grid is under pressure and keep buildings operating from stored power,” he says.