Distributed generation comes home: rooftop solar and batteries in NZ

In the mid-2000s, "distributed generation" was a phrase for conference papers. The idea was that instead of relying only on big power stations and long transmission lines, electricity could also be made in many small places close to where it is used: on roofs, in community schemes, at factories. Enthusiast sites, including the one that used to live at this address, wrote about local generators and "intelligent" power networks that would link them up.

In 2026 the idea is no longer exotic. Distributed generation in New Zealand mostly means one thing: solar panels on a house roof, sometimes with a battery in the garage. This piece explains how that works here and what a homeowner should think about first.

How home solar works in New Zealand

Solar panels turn daylight into direct-current electricity. An inverter converts it to the alternating current your house uses. During the day, the house uses solar power first. Any surplus flows out to the local network, and your retailer pays you for it, usually at a lower rate than you pay for electricity you buy.

That gap between the buy price and the sell price is the most important number in home solar economics. Power you use yourself saves you the full retail price. Power you export earns much less. So the best-value systems are sized and used so that as much of the generation as possible is used at home: running the dishwasher, washing machine, hot-water cylinder or EV charger in the middle of the day.

Gen Less, the government's energy efficiency programme, has a practical guide to working out whether solar suits your house, including orientation, shading and how much of your use falls in daylight hours.

Batteries: the second step, not the first

A home battery stores surplus solar for the evening, when demand and prices are highest. Batteries have become cheaper and more common, but they are still a significant extra cost, and for many households the sums are tighter than for the panels alone.

A sensible order is usually:

1. Reduce waste first: insulation, efficient heating and hot water.
2. Shift flexible loads, like hot water and EV charging, into sunny hours.
3. Add panels sized to what you can use.
4. Consider a battery later, once you have a year of real generation and use data.

Batteries also offer backup during outages, but only if the system is designed and installed to do that. Many standard installations shut down when the grid goes down, for the safety of line workers.

Start with the roof

Solar panels are expected to last for decades. Before they go up, it is worth asking whether the roof underneath will last as long.

• Age and condition of the roofing. Removing and refitting panels to replace a roof later is expensive. If the roof is near the end of its life, replacing it first often makes sense.
• Fixings and flashings. Every bracket is a hole in the roof. A good installer uses fixings and flashings suited to your roofing material and seals them properly.
• Structure. Panels and frames add weight and wind load. Older or modified roof framing may need checking.
• Corrosion zone. Near the coast, salt spray affects metal fixings and frames. Materials should suit the exposure.
• Access and maintenance. Panels can make it harder to inspect, clean or repaint the roof. Plan for that.

A roofer's opinion before the solar quote is cheap insurance.

The 2025 building consent exemption

Until recently, putting solar panels on a house roof could need a building consent, depending on the council and the system. That changed in late 2025. The Building (Exempt Building Work) Order 2025 added an exemption for roof-mounted solar arrays, which came into force on 23 October 2025.

In broad terms, panels mounted on a frame fixed to an existing roof no longer need a building consent if the total array area is 40 square metres or less and the site is not in a very high wind zone. Larger arrays, or sites with higher wind loads, can still be exempt if a chartered professional engineer designs or reviews the installation. The work must still comply with the Building Code, and electrical work must still be done and certified by a licensed electrician. We'll cover the detail in a separate note.

Connecting to the network

Before a system is connected, your local lines company needs to approve it. Your installer normally handles the application. The lines company checks that the system's inverter meets the required standard and that the local network can take the exported power. In some areas, export limits apply.

You also need to tell your retailer, who will set up a buy-back arrangement. It is worth comparing retailers' buy-back rates, which vary.

From "intelligent power networks" to everyday reality

The futurists of 2007 imagined a grid in which thousands of small generators worked together, smoothing out supply and demand automatically. Parts of that vision have arrived: smart meters, inverters that can respond to grid conditions, and retailers that pay households to shift their use. Our piece on smart grids looks at what actually reached New Zealand homes, and the wider energy section covers the rest.

The Level website from BRANZ has a good overview of on-site renewable generation for anyone designing or renovating a house.