Should I size solar now if an EV is coming?

An electric vehicle is one of the few household loads big enough to change a solar system NZ design on its own. Many cars use roughly 15 to 20 kilowatt-hours per 100 kilometres, so a 40 kilometre daily commute is often about 6 to 8 kilowatt-hours. That is a large slice of what a 5 kW array produces on a decent day, and a small slice of a dull winter day. The design question is when you will charge, not only how many panels fit.

If the car is parked at home through the middle of the day, solar can cover a real share of charging and the extra panels can earn their keep. If the car is at work until evening, the charger runs on the grid unless a battery is large enough to hold the noon surplus. Say which life you actually have. A 5kw solar system nz package aimed at a generic family will miss both cases.

Daytime charging versus overnight charging

Daytime charging needs the car at the house, a charger or a portable EVSE you can schedule, and a spare electrical capacity on the board. A simple timer or the car's departure setting can start the charge late morning. You then use solar power for the kilometres instead of exporting them.

Overnight charging is convenient and it uses off-peak rates on some plans. It does not use the array, except for whatever a battery stored. Do not buy a larger array solely for a car that will only charge after 11pm. Do consider the charger circuit, the tariff, and whether solar still makes sense for the rest of the house.

Workplace charging changes the home picture again. If most kilowatt-hours go in at work, the home array should be sized to the house, with a modest allowance for weekends. Tell the designer the split.

What to add to the kilowatts

Start from the house, using the size guide: https://homesolarinstallation.co.nz/blog/solar-system-size-nz/ Then add the EV energy you will actually charge at home in daylight. EECA's bands group many homes around 3 kW, 5 kW and 10 kW. A house that was a comfortable 5 kW design can become an 8 to 10 kW conversation once a car is charged at home several days a week. It can also stay at 5 kW if the car is never there at noon.

Inverter headroom matters. If the car arrives in eighteen months, it is often cheaper to fit an inverter and a roof layout that can take more panels later than to rebuild the plant. It is not cheaper to buy every panel now if they will be clipped by an export limit for a year and a half. The add-later questions are real. Ask the installer what a second stage costs in scaffold and network paperwork.

A 5kw solar system price nz figure from a national table will not include the charger circuit. Price the charger separately and say whether it is in the solar contract.

Export limits and a car that is gone at noon

Extra panels that cannot be used in the house and cannot be exported are a weak buy. If your lines company caps export, a car that is away at midday does not relax the cap. The inverter will still reduce output when the cap is reached. Read the export guide before you jump from 5 kW to the largest array the roof can hold: https://homesolarinstallation.co.nz/blog/solar-export-limits-nz/

A battery can hold noon energy for an evening charge. That is a lot of storage for a commute, and EECA's guidance is that batteries usually lengthen payback. Run the numbers with your tariff. A cheaper night rate plus a right-sized array for the house can beat a large battery bought only so the car can feel solar-powered.

The battery guide sets out when storage belongs in version one: https://homesolarinstallation.co.nz/blog/solar-battery-storage-nz/

The charger is its own electrical job

A dedicated charger is a high-current circuit. The switchboard has to have the ways, the main supply has to have the capacity, and the cable route has to be real. Load management can slow the charger when the oven and the inverter export settings would otherwise overload the mains. Ask for that in writing if the house is single phase.

This work is licensed. A solar installer may include it or exclude it. Either is acceptable if the quote says which. A board that is already tight should be priced before you order the car and the panels in the same month. Board notes are here: https://homesolarinstallation.co.nz/blog/solar-switchboard-upgrade-nz/ and a licensed electrician such as Tromar can assess the board: https://tromarelectrical.co.nz/

Three-phase houses have more room to share charging and export. Single-phase houses should hear a plain explanation of the limit. If the quote cannot explain it, ask until it can.

Tariffs and the bill you are planning

Some retailers sell an EV night rate and a solar buy-back on the same account. The night rate can make overnight charging cheap enough that solar for the car is a weak extra. The day rate can make daytime solar charging more valuable. Compare the whole plan: import, daily charge, buy-back, and any EV window. Powerswitch lists solar rates: https://www.powerswitch.org.nz/solar-rates

EECA's cost bands, about $8,500, $11,500 and $20,000 for the small, medium and large arrays before a battery, are the hardware context. An EV does not change GST or the need for a written scope. It changes the kilowatt-hours you are trying to cover. Cost detail is here: https://homesolarinstallation.co.nz/blog/solar-panel-cost-nz/

Payback still depends on self-consumption. The worth-it guide is the annual test: https://homesolarinstallation.co.nz/blog/is-solar-worth-it-nz/

What to say in the quote request

Give the designer a short brief and keep a copy.

• Car arriving when, and kilometres you expect to charge at home each week
• Whether the car is home between 10am and 3pm on weekdays
• Charger included in this quote or priced later
• Export limit assumed, and whether the inverter can take more panels when the car arrives
• Single phase or three phase, and whether the board has room

Commutes and driveways differ across these places

Solar and EV charging for homes in 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 depends on where the car sits at noon. A Devonport, Bayswater, Belmont or Takapuna household that commutes into the city may not charge until evening. A work-from-home house in Coatesville, Dairy Flat, Riverhead, Kumeu or Huapai may have the car under the array most days. Rural kilometres around Wellsford, Helensville, Waimauku and Kaukapakapa can be longer, so the weekly kilowatt-hours are larger if you charge at home. Kawau Island access is a different problem again: freight and travel belong in the install price, and the car may not be the main load.

Home Solar Installation NZ can introduce a local partner. The form is free and there is no obligation. Put the car in the comments so the first design is not a house-only template. EECA's planning notes are here: https://www.eeca.govt.nz/for-homes/solar-for-homes/plan-your-solar-system/