MainPower solar export limits and connection approval explained

Are you on MainPower’s network?

MainPower describes its network as running from north of the Waimakariri River, through the Waimakariri and Hurunui districts, to Kaikōura. That takes in Rangiora, Kaiapoi, Oxford, Amberley, Hanmer Springs and Kaikōura. South of the river you are almost certainly on Orion, and Orion’s export rules are different: do not carry a figure from one company to the other.

Near the boundary, the address will not settle it. Your ICP number will. MainPower describes the ICP as a unique 15-character code and says you can find it on your latest power bill or with the Electricity Authority’s My Meter tool. Your power retailer can also tell you which lines company the ICP belongs to. Our Canterbury lines company table covers the other three networks.

Keep the three roles apart. MainPower approves the connection and sets the export limit. Your retailer sets the price you are paid for exported power and arranges the import/export meter. Your installer designs the system and normally lodges the application.

The 10 kW default

MainPower’s solar and distributed generation page says a small-scale residential or business customer’s default limit for exporting power is 10 kW. It says it now approves up to 10 kW for single-phase installations, and that three-phase installations are assessed case by case. It can set a lower limit where the local network is constrained.

This matches the national rule. The Electricity Authority changed the Electricity Industry Participation Code in 2026 so that a straightforward home connection of up to 10 kW gets a 10 kW default export limit, and a lines company that wants to set a lower one has to justify it with a standard network assessment. Those changes took effect on 11 May 2026.

An export limit is measured in kilowatts, which is power at one moment. It is not a daily allowance in kilowatt-hours. A 10 kW limit rarely bites on a home system: you would need more than 10 kW of spare output after the house has taken what it is using. A 2 kW limit bites on most sunny days. Our system sizing guide explains how panel size, inverter size and export fit together.

The 168 connections with a lower limit

MainPower publishes a list of ICPs with a permitted export limit below 10 kW, which the Code requires. The current list says it is accurate as at 22 July 2026 and holds 168 connections. We counted them by limit and by the reason MainPower gives.

Three in four of the limited connections are on SWER lines. These are the rural lines that carry power on a single wire and use the ground as the return path, common on long runs to farms and back-country houses. MainPower says SWER sections have less capacity for export and are more sensitive to voltage, earthing and protection problems. Every SWER connection on the list is held to 2 kW.

The 35 voltage cases are all set to zero export. MainPower’s explanation is that more export there could push the local voltage above the permitted range, which it says is a particular risk on long or lightly loaded lines. The last three are places where the local transformer has little spare capacity.

Put in proportion, 168 is a small number. EMI figures for 31 August 2026 show 3,130 homes with solar on MainPower’s network, 8.3% of its residential connections, which works out at about 37,500 homes. So well under one connection in a hundred is on the list. If yours is one of them, though, it changes the whole design.

What a 2 kW or 0 kW limit does to a quote

New home systems on MainPower’s network averaged 7.8 kW in the year to August 2026, according to our Canterbury solar statistics. On a clear summer day a system that size can produce several kilowatts more than the house is using for hours at a time. With a 10 kW limit all of that surplus is exported and paid for. With a 2 kW limit, anything above 2 kW has to be used on the property or the inverter holds it back.

That does not make solar a bad idea at a limited address. It changes what is worth buying:

• Size for what you use, not for what you could sell. A forecast that counts exports the connection cannot carry will overstate the savings.
• Move load into the day. Hot water is the usual first step. Our guide to timers, diverters and batteries for hot water compares the options.
• Price a battery on its own merits. Stored power you would otherwise lose is worth the full retail rate when you use it later, which improves the case set out in our battery or no battery guide.
• Ask what it would take to lift the limit. A limit is a limit on export, not on generating. Ask MainPower whether an export-limited system is acceptable at the address and whether any network work would change the figure, and who would pay for it.

Rural owners should also read our guide to solar on lifestyle blocks, which covers long cable runs, sheds and pumps.

What MainPower charges to apply

MainPower’s page lists these fees, which it says apply from 1 October 2026, are payable on invoice and exclude GST.

For an ordinary house that means no lines company fee, where Orion and EA Networks both charge one. The jump comes above 10 kW: $770 plus $180, or $1,092.50 with GST added. A large roof on a lifestyle block or a farm shed can cross that line, so ask the installer whether a slightly smaller inverter would keep the system in the no-fee band and what that would cost in output.

The schedule’s bands read “under 10 kW” and “more than 10 kW”. If the proposed system is rated at exactly 10 kW, have the installer confirm with MainPower which band applies before the quote is final.

Inverter and voltage rules

MainPower requires the inverter to comply with AS/NZS 4777.2:2020 and to be on the Clean Energy Council’s approved inverter list. Its page also names the installation standards the electrician works to, including AS/NZS 4777.1:2024, AS/NZS 5033 and AS/NZS 3000. Ask the installer to write the exact inverter model on the quote so it can be checked against the approved list.

Voltage is the reason many solar systems export less than their owners expect. An inverter must reduce its output, and eventually switch off, when the voltage on the street rises too far. MainPower notes that in June 2025 the Government widened the permitted low-voltage range from 230 V plus or minus 6% to plus or minus 10%, which is 207 V to 253 V where it used to be 216 V to 244 V. It says inverters installed since then should be less likely to cut exports because of voltage.

If you already have solar and see it dropping out on bright days, ask your installer whether the inverter’s settings date from before that change.

From application to switching on

MainPower’s Network Connection Standards are blunt on the first point: generation that could export to the network cannot be connected without first applying. The steps below come from its solar page and those standards.

1. Talk to MainPower before applying. It recommends contacting its Network Services Representative team first, on 0800 30 90 80 or nsr@mainpower.co.nz. This is the moment to ask about a constraint at your address.
2. Have the installer or electrician complete the forms. MainPower recommends this because the forms need a good understanding of electricity. Applications go through MainPower’s online portal.
3. Tell your retailer. The standards require you to notify your electricity retailer so the right metering can be installed. Ask what the meter change costs and which plan will pay for your exports.
4. Wait for approval, then install. Any fee is invoiced. Keep the written approval and the export limit it states.
5. Get the paperwork in on time. The standards say certification of the installation must occur within 10 days of commissioning, and that MainPower may isolate a supply with generation if the documents do not arrive in time.

MainPower’s solar page does not publish a target approval time. Ask the installer for the date the application was lodged, and do not book the installation until the approval is in hand.

When MainPower can turn your export down

An approved limit is not a promise that you can always export that much. MainPower says export may be curtailed at times to keep the network safe, and lists the situations in which it may interrupt, curtail or temporarily disconnect generation:

• planned maintenance, construction or repairs on the network;
• an emergency, or to protect people or property;
• unauthorised changes to the system that materially alter what it sends into the network;
• obligations placed on MainPower by others, such as Transpower or the law;
• too much generation on one part of the network, causing problems such as excessive voltage.

The last one matters in a district where one home in twelve already has solar. North Canterbury ranks third of 38 local network areas in our regional solar rankings, and the more panels a street has, the more often midday voltage becomes the limit.

One more rule for properties with two connections, such as a house and a separately metered shed or pump. MainPower charges per physical ICP and does not support netting generation at one ICP against use at another. Panels on the shed will not reduce the house’s bill unless both run through the same connection.

Batteries, EVs and existing systems

MainPower’s standards list batteries alongside solar panels and wind turbines as generation that could export, so a battery that can feed the network needs an application too. Its solar page treats an electric vehicle or charger that can export, known as vehicle-to-grid, the same way, and says it may ask for the device type, inverter details and maximum import and export capability.

If your existing system was approved when lower limits were normal, MainPower’s statement that it now approves up to 10 kW on single phase is worth following up. Its page does not set out a separate process for raising the limit on an existing system, so contact MainPower before anyone touches the inverter settings. An unauthorised change is one of the listed grounds for disconnection.

Do not carry Orion’s winter peak export credit into a North Canterbury forecast either. That payment is Orion’s, and MainPower’s solar and pricing pages do not mention an equivalent. What your exports earn is set by your retailer: see our buy-back rate guide.

Six things to get in writing

• The connection: the ICP, confirmation that it is on MainPower’s network, and whether the supply is single-phase or three-phase.
• The list check: whether the ICP appears on MainPower’s below-10 kW list, and the date of the list that was checked.
• The export assumption: the limit the savings forecast uses, and a second forecast at a lower limit if approval is still pending.
• The equipment: panel capacity and the exact inverter model and rating.
• The fees: whether the system is under 10 kW, and who pays MainPower and the retailer’s meter charge if not.
• The paperwork: who lodges the application, who notifies the retailer, and who sends the certification within 10 days of commissioning.