Why do some streets limit solar export?

An export limit is a cap, in kilowatts, on how much power your inverter may send into the street at once. Lines companies use it because the local transformer and the voltage on the line can only absorb so much generation in the middle of a sunny day. Solar electricity NZ households export is useful. It is not unlimited, and the limit is a property of your connection, not of the panel brand.

The cap is different from the size of the array. You can have more panels than you are allowed to export. When the house is not using the surplus and the cap is already met, a compliant inverter reduces output. From the footpath the system looks idle. On the monitoring app it is doing what the approval required. People call that a fault. Often it is the design they paid for without reading the cap.

Why the cap exists

Rooftop solar on one house is small. Many houses on one transformer, all peaking at noon, are not. Voltage rises when generation exceeds what the line and the local loads can soak up. The lines company keeps voltage inside the range appliances expect. Export limits, inverter settings and, on some networks, flexible export are the tools.

The limit is decided in the distributed generation application, using your address and the proposed inverter. Two neighbours can have different caps. A new transformer or a quieter street can be more open than a street that already has a lot of solar power systems. Ask for the figure that applies to your ICP. A regional average is not an approval.

Single-phase homes more often meet a tighter cap than three-phase homes, because the power lands on one line. If you are choosing between a larger array and a three-phase upgrade, put both prices next to the cap. A board upgrade does not silently raise the export limit. The network still has to agree. See the switchboard guide on this site and the application guide before you assume the wires will take everything the roof can hold.

What clipping does to the savings story

Every kilowatt-hour you use in the house avoids the retail import price. Every kilowatt-hour you export earns the buy-back rate, which is lower. Every kilowatt-hour you clip earns nothing. Once a cap is binding, extra panels earn less than the brochure's unconstrained annual yield.

That is why sizing from the roof area alone is weak. The size guide starts from your annual kilowatt-hours and your daytime load, then fits the roof and the network: https://homesolarinstallation.co.nz/blog/solar-system-size-nz/ EECA's example bands, about 3 kW, 5 kW and 10 kW, are conversation sizes. A 10 kW array on a connection that can export far less will not perform like an unconstrained 10 kW array in a savings calculator.

Ask the installer for an annual yield that includes the export limit, not a perfect north-roof number with no cap. If two quotes disagree, ask both to show the cap they assumed. The buy-back guide explains why a slightly higher export rate does not rescue clipped energy: https://homesolarinstallation.co.nz/blog/solar-buyback-rates-nz/

Ways to use power that would otherwise be clipped

The first lever is the house. A hot water cylinder on a midday timer, a dishwasher, a washing machine, and a heat pump that can run while the sun is up all raise self-consumption. You are not beating the cap with a letter to the lines company. You are using the electricity before it has to leave.

An EV charged at home during the day can soak up a large block of kilowatt-hours, if the car is actually there. Overnight charging does nothing for a noon cap. Say which pattern you really have.

A battery can store surplus that would have been clipped and release it in the evening. EECA's public position is that a battery is optional and that solar without storage usually pays back better. A cap can be one of the cases where storage earns a closer look. It is still a cost, often about $5,000 to $15,000 on top of the array, and it needs a yield model with the cap included. The battery guide is here: https://homesolarinstallation.co.nz/blog/solar-battery-storage-nz/

Questions for the quote

Put the cap on the same page as the kilowatts.

• What export limit applies at this address, and is it export capacity or a flexible arrangement?
• What annual kilowatt-hours does the model show with that limit, not without it?
• What happens at noon on a clear weekday if nobody is home?
• Does the inverter size assume we might add panels later, or would that need a new approval?
• Who tells the retailer, and which plans accept this system size?

Retail plans do not lift a network cap

A generous buy-back rate does not raise the kilowatts you are allowed to push into the street. The retailer pays for exported energy that the network accepted. Clipped energy never becomes a bill credit. Compare plans on import rate, daily charge and buy-back together, using Powerswitch: https://www.powerswitch.org.nz/solar-rates

Some plans cap the system size they will accept. A large array can be approved by the lines company and still be awkward on a particular retailer offer. Check both before you order hardware.

Switching retailers after solar is usually possible. Take the approval, the inverter model and the export limit with you so the new retailer can set the account up without guessing.

How to talk about it without a fight

Ask for the cap in the first design, not after the panels are paid for. If the installer shrugs, ask them to lodge a preliminary question with the lines company or to state the cap they are assuming in writing. An assumption you can see is better than a yield you cannot.

If the cap is tight and your daytime use is low, a smaller array can be the better purchase. Paying for kilowatts that will be clipped every summer noon is a hardware hobby, not a bill plan. EECA's costs page is the public price context: https://www.eeca.govt.nz/for-homes/solar-for-homes/solar-costs-and-savings/

Home Solar Installation NZ can introduce a local partner for a written design. The form is free and there is no obligation. Ask them to show the export assumption beside the kilowatts.

Caps are local, including these suburbs

Export limits for solar power are set per connection across Algies Bay, Arkles Bay, Army Bay, Big Omaha, Coatesville, Dairy Flat, Dome Forest, Dome Valley, Glorit, Gulf Harbour, Hatfields Beach, Helensville, Huapai, Kaukapakapa, Kawau Island, Kumeu, Leigh, Matakana, Muriwai, Omaha, Orewa, Puhoi, Riverhead, Snells Beach, South Head, Waimauku, Warkworth, Wellsford, Bayswater, Belmont, Campbells Bay, Castor Bay, Devonport, Forrest Hill, Hauraki, Milford, Narrow Neck, Stanley Point, Sunnynook and Takapuna. North Shore streets that already have a lot of solar panels, and longer rural feeders around Helensville, Waimauku, Kaukapakapa, Glorit, Dome Valley and Wellsford, will not share one number. Coastal houses in Orewa, Gulf Harbour, Leigh and on Kawau Island still need the ICP checked. Copying a Takapuna neighbour's system size is not a design.

Use your own bill and your own approval. The public note on savings from using solar in the house first is here: https://www.eeca.govt.nz/for-homes/solar-for-homes/solar-costs-and-savings/