Powering your home with your electric vehicle: Trio of trials underway

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Three NZ trials underway but a number of challenges to overcome before it goes mainstream.

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James Ryan plugs his EV into a two-way Starcharge charger, which can charge the car or draw power from its battery to run the Aucklander's home. Photo / Chris Keall

Powering your home with your electric vehicle sounds a bit futuristic.

But one Auckland family has made it a reality for the past three months and others in the South Island are also trialling the technology, with a broader North Island trial about to begin.

Remuera residents James and Carolyn Ryan and their daughter have been powering their home via the electric vehicle (EV) in their driveway since mid-year.

The usual set-up is a one-way charger. Power flows from the grid (your home) to top up your EV.

But under a Genesis Energy-managed trial, a StarCharge two-way charger was installed at the Ryans’ home.

That meant the BYD Atto 3 parked outside their front door could power all the appliances in their house, from their hot water cylinder to their oven, dishwasher and TV – essentially everything usually charged via the grid.

Beyond the Genesis trial, a pilot is underway in the South Island by the Queenstown Electrification Accelerator, so far involving half a dozen homes, with another 30 or so to be added later this year and into early 2027.

Meanwhile, Counties Energy-owned OpenLoop is setting up a trial for 100 sites that will span homes, fleets and businesses around the North Island.

Crown agency EECA (the Energy Efficiency and Conservation Authority) is bankrolling the Queenstown trial (to the tune of $900,000) and the OpenLoop effort (chipping in $2.1 million), with its funds covering chargers and installation costs.

There are three scenarios for two-way charging (also called bidirectional charging or vehicle-to-grid):

1. Using your EV to run your home during a power cut or natural disaster. With an average-sized EV and average-sized home, the electric vehicle’s battery (typically three or four times the capacity of a home solar battery) should be able to power the home for about nine hours, or more than a day, if you’re careful, Counties Energy chief network and digital officer Moonis Vegdani said.

2. Using your EV to run your home during normal times, or some of them. You can save an estimated $2000 a year by buying power in the middle of the night or day, when it’s cheap, storing it in your car’s battery, then discharging it back to your home during peak times, plus selling excess power back to the grid. StarCharge’s app can be used to manually start charging your EV or discharging power from the vehicle to your home, or to schedule the process to run on autopilot – once you’ve plugged your EV into the charger outside. The $2000 savings figure comes from Concept Consulting research commissioned by ECCA. Genesis says it’s too early to estimate savings.

3. Helping to ease pressure on the grid during the likes of a winter cold snap, preventing brownouts or price spikes. Forsyth Barr said in a note it estimates battery-electric vehicles on New Zealand roads contain about 7000MWh, or 7GWh, of storage capacity – more than 10 times the country’s installed grid-scale battery capacity.

For context, the country’s hydro lakes held about 4660GWh at the start of October. That’s about 105,000 EVs on our roads, or about 2.3% of New Zealand’s vehicle fleet (there are also 54,000 plug-in hybrids, typically with much smaller batteries).

With enough cross-industry co-operation (and allowance for the fact a big slice of that power will be needed for driving), vehicle-to-grid (V2G) technology means those EVs can act as a huge, virtual power station. This could “potentially defer or reduce future network investment”, EECA says.

Carolyn Ryan said the V2G system was easy to use and the family didn’t notice any difference in electricity supply while drawing from the car’s battery.

The strongest results were seen during evening periods when household electricity use was high. During one three-hour event, the home used more than 16kWh of electricity, with less than 1kWh of that coming from the grid – the rest came from the car’s battery.

When the Herald turned up, the Ryans were into phase two of their trial, with a Geely EX5 plugged into their home. Polestar and Zeekr cars will follow (all three come from Giltrap Group subsidiary NordEast).

When will V2G go mainstream?

So when can we all be like the Ryans?

Genesis says vehicle-to-home charging could be about two years from going mainstream.

Today, there are several barriers.

One is that using your EV to charge your home will invalidate your car’s battery warranty – and its battery array accounts for about a third of the value of an electric car.

BYD NZ and Giltrap Group had to organise special warranty exemptions for the Genesis trial.

Without proper hardware and software in your EV, and proper synchronisation with a V2G charger and power company systems, there’s a chance vehicle-to-home charging could cook your battery.

BYD NZ says from 2027, most vehicles it sells across its range will support vehicle-to-home charging (but the 15,000 or so already on the road will not be software-upgradeable to support it).

NordEast says it’ll offer V2G support for most models from mid-2027. Most cars in its stable should be software-upgradeable if they’ve been bought in the past year or so.

Then there are steep set-up costs.

The StarCharge Halo bidirectional 7.4kW DC charger used by the Ryans costs $6000.EECA strategy manager Murray Bell said the Queenstown trial has found installation costs are about $7000 to $8000 on top of that for total upfront costs in the $13,000 to $14,000 range.

That is more expensive than a one-way 7.4kW smart home charger that can be picked up for under $1000, plus potentially the same again for installation if wiring or a switchboard needs upgrading.

But over time, we should see economies of scale kick in for bidirectional chargers. Today, there are only two models available for local trials – from China’s StarCharge and Sig Energy – but local player Evnex and others are assessing the technology, and many are expected to climb on board once it’s heading for the mainstream.

Right now, power companies around the world are at the trial phase.

NordEast general manager Dane Fisher said the installation costs EECA has racked up in Queenstown reflect that electricians have had to spend a lot of time on site doing exploratory work for the all-new tech.

Fisher estimated that once V2G chargers are produced at scale, more tech is supported on board EVs, and electricians get up to speed, a charger and install will cost about $4000 in total – meaning a household could recoup its investment within a couple of years.

Bell also pointed out there are complications to work through. For example, properties with solar and batteries already have a home management system.

And using a V2G system during a blackout can, without proper management in place, cause a lines company headaches. If crews are working on a section of damaged line during a natural disaster, the last thing they need is surplus power from an EV suddenly appearing on the grid (and for that reason, Genesis has yet to enable power cut cover for its Auckland trial).

But the EECA executive said those are the sorts of issues the various trials are designed to iron out.

Fisher identified two factors driving the recent surge in EV sales: Chinese models reaching parity with petrol cars, and the Iran conflict causing pain at the pump and amplifying electric vehicles’ cost-of-ownership advantage.

He expects support for vehicle-to-home charging to become the third plank from next year.

Chris Keall is an Auckland-based member of the Herald’s business team. He joined the Herald in 2018 and is the technology editor and a senior business writer. He has recently written about EV sales surging to a record high in 2026 and an NZ-made home battery that lets you be your own gentailer.

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