How EVs tie into your home energy system

Reframe the car

A typical EV carries 50-80 kWh of battery - four to six times a large home battery. Once you see the car as a rolling energy asset rather than just a load, the whole home-energy picture reorganises around it: it's simultaneously your biggest consumer, your biggest storage device, and potentially a grid participant.

Today, most of the value is in the first role done intelligently. The second and third are arriving - and are worth designing for now.

Today: the EV as smart load

The practical, available win is directing your solar into the car. Solar-aware chargers modulate charging in real time to match your export surplus, so the car soaks up energy that would otherwise earn single-digit feed-in cents. Combined with off-peak overnight top-ups on a time-of-use plan, home charging costs collapse against both petrol and standard-rate grid charging.

Our companion article covers the practical charging setups; the design implication here is simpler: an EV in your two-year horizon should be declared in your solar design today, because panels are cheapest at initial install and roof space reserved is cheaper than a second visit.

Arriving: the car as a power source

Vehicle-to-Load (V2L) is already common on newer EVs - a socket powering appliances from the car, genuinely useful in an outage even without any home integration. Vehicle-to-Home (V2H) and Vehicle-to-Grid (V2G) are the bigger step: bidirectional charging that lets the car run your house through the evening peak or sell into the grid at peak prices.

Australia has moved from trials toward real availability - standards and approvals for bidirectional charging have been progressing, compatible vehicles and chargers are appearing, and the economics are compelling on paper: an EV doing evening-peak duty dwarfs a wall battery's capacity. The honest caveats: hardware remains the expensive piece, vehicle warranty positions on bidirectional use vary by manufacturer, and current availability changes fast enough that we check it live at design time rather than print it here.

Does V2G make the home battery redundant?

Not neatly. The car leaves the house - usually at exactly the times storage matters - while a wall battery never does; backup that depends on the car being home isn't backup you can plan on. The emerging pattern for high-electrification homes is complementary: a right-sized stationary battery for reliability and daily cycling, the EV as bulk storage and opportunistic peak asset when present.

What we design for today: EV-declared array sizing, charger circuit and switchboard provisioning, and hardware choices that keep the bidirectional door open. That way the ecosystem arrives as an upgrade, not a rebuild.