Electric vehicles and home batteries are increasingly being purchased together — and for good reason. A home battery can maximise the proportion of your driving powered by solar and smooth out the evening energy demand. But the two systems interact in ways that affect sizing, switchboard requirements, and economics, so it pays to understand the relationship before you buy.
How much power does EV charging actually draw?
In Australia, almost all residential EV charging happens on Level 2 AC chargers. The power your charger can deliver depends on two things: your home's power supply and your vehicle's onboard charger.
Most Australian homes have single-phase power, which limits AC charging to a maximum of about 7.4 kW (240 V × 32 A). That's enough to add roughly 40–50 km of range per hour — more than adequate for most overnight charging needs.
Three-phase power unlocks higher charging rates. An 11 kW charger on three-phase adds around 70–80 km per hour; a 22 kW charger adds up to 130 km per hour. However, only around 30% of Australian homes have three-phase supply, and few EVs currently sold here support 22 kW AC — most cap out at 7.4 kW or 11 kW regardless of what the charger can supply.
Practical implication: for the large majority of Australian EV owners, a 7.4 kW single-phase charger is the right choice. Upgrading to three-phase costs $2,000–$5,000 with your network operator and rarely makes financial sense for home charging alone.
How much energy does an EV use?
Energy consumption for popular Australian EV models sits roughly in this range:
- Compact EVs (MG4, BYD Atto 3): 14–16 kWh per 100 km
- Mid-size sedans (Tesla Model 3 RWD): around 14–15 kWh per 100 km
- Family SUVs (Tesla Model Y, Kia EV6): 16–20 kWh per 100 km
A typical daily commute of 40 km therefore consumes approximately 6–8 kWh — a manageable load for a home battery system. AWD variants of any model use 15–25% more energy than their RWD equivalents.
Solar-direct charging versus battery-mediated charging
There are two distinct ways to charge your EV from solar, and the distinction matters for how you size your system.
Solar-direct charging happens when your panels are generating more electricity than your home is consuming and that surplus flows directly to your EV charger. If you're home during the day — or can programme your charger to start around midday — this is the cheapest approach and requires no battery at all. Most modern smart chargers can detect surplus solar and throttle the charge rate to match available generation.
Battery-mediated charging is for households who aren't home during the day. The battery accumulates surplus solar while you're out and then discharges into the EV charger when you plug in after work. This is where a home battery earns its keep in an EV household: it bridges the gap between when solar peaks (midday) and when you want to charge (evening).
One practical gotcha: a 7.4 kW EV charger draws more power than most home batteries can sustain for long. A typical home battery discharges at 5–10 kW. If your charger is drawing 7.4 kW and your battery can only supply 5 kW, the remaining 2.4 kW will be drawn from the grid. To charge a full EV battery (~60 kWh) from a home battery alone would require an unrealistically large home battery. The realistic goal is to top up the daily commute distance — 6–8 kWh — not to fill an empty EV overnight.
How much does EV charging add to your battery size?
As a rule of thumb, each kilometre of daily EV travel you want to power from stored solar adds roughly 0.18–0.22 kWh to your battery requirement (accounting for ~90% battery round-trip efficiency and ~90% AC charging efficiency combined).
For a 40 km daily commute powered by stored solar, add approximately 7–9 kWh to your battery sizing estimate. For most households this pushes the recommended battery from the 10 kWh range up to 13–15 kWh or more.
Our calculator includes an EV load toggle that adjusts the battery and solar size recommendation for your specific commute distance.
What to check at your switchboard before installing an EV charger
Before any quote becomes a contract, your electrician needs to assess your switchboard. This step is often overlooked and can add significant cost.
- Available breaker slots. A dedicated 32 A circuit is required for a 7.4 kW charger. Older boards — particularly fuse-based boards common in pre-1990s homes — frequently need replacement. Switchboard upgrades typically cost $900–$3,500.
- Main fuse rating. Adding 32 A of continuous EV charging load on top of a battery inverter, air conditioning, and other household circuits can exceed the rated capacity of an older main fuse. Your electrician must verify the total load.
- DNSP notification. In NSW, VIC, QLD, and SA, a 32 A single-phase charger triggers a notification requirement to your distribution network service provider (DNSP). Your installer should handle this, but confirm it's covered in the quote.
If you're also adding a battery inverter at the same time, the combined grid connection capacity implications need to be reviewed together — not treated as two separate jobs.
Do you need to upsize your solar system?
Adding an EV to a home that already has solar is often the right trigger to review whether your existing system is large enough. An EV adds roughly 2,500–3,000 kWh per year to household electricity consumption.
A system that was comfortably covering your household load before the EV may now be undersized. Most installers recommend at least 10 kW of solar for a household with one EV, rising to 13 kW or more if you also want to fill a home battery daily. Oversizing solar is almost always more cost-effective than increasing battery capacity — more generation gives both systems more to work with.
Smart charging integration
OCPP (Open Charge Point Protocol) is the open standard that lets a home EV charger communicate with third-party energy management platforms. OCPP-compatible chargers — including the Evnex E2 range, the Ocular IQ Home Solar, and several Wallbox models — can be integrated with your battery inverter's energy management system or with apps like ChargeHQ and Amber to automate charging from surplus solar.
Without smart charging integration, you're likely scheduling the charger by time-of-day rather than by actual solar surplus, which is less efficient and can cause the EV charger to compete with the home battery for the same solar. A properly integrated system tells the charger to throttle back when the battery is below a threshold, or to charge harder when surplus solar would otherwise be exported.
If you're investing in a combined solar + battery + EV system, budget for an OCPP-compatible charger. The price premium is usually $200–$500 over a basic charger and pays back quickly in smarter energy dispatch.
Bidirectional charging (V2H and V2G) in Australia
Bidirectional charging — where the EV battery exports power back to your home (V2H) or to the grid (V2G) — has been discussed as a technology that could make a dedicated home battery redundant. The reality in mid-2026 is more nuanced.
The regulatory framework is in place but the ecosystem is immature. AS/NZS 4777.2:2020 and the updated AS/NZS 4777.1:2024 permit bidirectional charging. Australia's first CEC-approved bidirectional charger — the Numbat/Infy Power 6.2 kW unit — received approval in late 2025, with others expected through 2026. RedEarth Energy has pre-orders open for a V2G charger retailing around $9,990 plus GST.
Compatible vehicles in Australia remain limited. Most EVs currently sold here have the hardware for bidirectional charging but manufacturers have not yet enabled it. The Nissan Leaf (CHAdeMO) supports V2H with compatible chargers, but CHAdeMO is a legacy connector. The Kia EV9 supports V2G via CCS2 in some configurations. Most other popular models — Tesla, BYD, MG — do not currently offer V2H or V2G capability in Australia.
V2H does not simply replace a home battery. Using your EV as a home battery degrades its cells over time with additional charge cycles, shortens its available range if the home draws heavily overnight, and requires you to keep the car plugged in — which suits households where the vehicle parks at home most nights but is impractical for shift workers or households with irregular schedules. It is a compelling future option for the right household, not a plug-and-play battery replacement today.
A well-sized combined system
For a typical Australian household with one EV and moderate daily driving:
- 10–13 kW solar — the higher end if your roof allows; more generation fills both the battery and the EV
- 13–15 kWh home battery — sized for household evening load plus daily EV commute top-up
- 7.4 kW single-phase OCPP-compatible EV charger — sufficient for overnight or daytime charging; three-phase only if your home already has it
This combination can cover the majority of household electricity consumption and power most daily driving from solar. The economics improve substantially once petrol costs are displaced — at current fuel prices, solar-charged driving costs roughly 2–4 cents per kilometre versus 15–20 cents for a petrol equivalent.
Use our calculator to model your specific situation — it accounts for your location, roof size, commute distance, and tariff structure to give you a realistic payback estimate.