Auckland trial tests using EVs as home batteries to cut bills and boost resilience

New Zealand's Energy Efficiency and Conservation Authority (EECA) is launching a larger trial in Auckland and other urban areas to see whether electric vehicles can act as "giant batteries" for homes and the grid. The trial will install up to 100 two-way chargers at participating homes and businesses. Two-way chargers allow EVs to charge normally and then discharge electricity back to a house, business, or the national grid.

The trial aims to test whether vehicle-to-household (V2H) and vehicle-to-grid (V2G) setups can lower household electricity bills by charging EVs when prices are low and using or selling power at higher prices. EECA says a fully charged EV could help a household through storms or other power outages for "up to three or four days" because modern car batteries are large. The approach could also reduce peak demand on distribution networks, potentially avoiding the cost of extra poles and wires as electricity use rises.

• Technical compatibility of vehicles with two-way chargers.
• Practical installation issues in real homes, including older wiring and charger siting.
• Safety concerns about third-party equipment interacting with car batteries.
• Performance during network outages and how chargers behave under real conditions.

Constraints and risks the trial will explore

There are only a few compatible combinations of EVs and two-way chargers available in New Zealand today. Vehicle manufacturers have expressed concerns about third-party equipment affecting battery performance. Older house wiring raises safety concerns. Practical matters such as where to place a charger can also limit uptake. The trial's aim is to identify solutions to these problems so deployment can be simpler — ideally plug-and-play for owners.

EECA says it will publish findings regularly. The evidence will inform future policies and guidance to enable effective two-way charger rollout across New Zealand. Counties Energy will feed back information about charger performance and behaviour during outages.

Look for published trial findings, which should cover compatibility lists of EV models and chargers, practical installation guidance, observed impacts on household bills, and recommendations for regulators and network operators.