Charging an electric vehicle with solar: Sizing and setup essentials
Australia's rooftop solar boom now meets a fast-growing electric vehicle market, offering households a natural path to drive on sunshine. With over three million rooftop PV systems installed nationwide, the country is well placed to power the next wave of transport electrification directly from home arrays. This guide focuses on practical sizing and setup decisions that determine whether your solar system can keep both your house and your car running on photons.
The financial case is compelling. Australian retail electricity prices in many states push past thirty cents per kilowatt-hour during peak periods, while petrol remains volatile. A solar-charged EV shifts transport fuel costs toward the upfront hardware, then drops marginal running costs close to zero. Choosing the right array size, inverter capacity, and charger type converts sunlight into kilometres without sending much back to the grid.
Several variables shape this equation: how far you drive each day, your roof orientation and shading, the capacity of your existing inverter, and whether you plan to add batteries. Local tariffs and rebates also tilt the math, particularly in Victoria, Queensland, and South Australia where feed-in rates and time-of-use windows vary widely. Treating the solar array and the EV charger as one integrated system, rather than two separate purchases, is the key to a setup that performs well year-round.
Before adding panels or buying a wallbox, it helps to understand how Australian homes actually use electricity. Most detached houses with a mid-sized rooftop array still draw significant power in the evening when solar production falls, while EVs parked in garages often sit idle for eight to twelve hours overnight. Designing the system around these rhythms, rather than peak solar output alone, determines whether the setup genuinely offsets transport energy.
Reading your electric vehicle's daily energy budget
A standard EV in Australia consumes 15 to 20 kWh per 100 km, depending on model, speed, and climate control use. A typical 40 km daily commute draws 6 to 8 kWh, roughly 2,200 to 2,900 kWh per year. Adding an EV often doubles household electricity consumption that previously came from a mix of grid power and solar export.
Popular models in the local market illustrate this spread clearly:
| Model | Battery size | Typical consumption | Annual kWh for 15,000 km |
|---|---|---|---|
| BYD Atto 3 | 60.5 kWh | 16.8 kWh/100 km | 2,520 kWh |
| MG ZS EV | 51 kWh | 17.5 kWh/100 km | 2,625 kWh |
| Tesla Model 3 RWD | 60 kWh | 15.2 kWh/100 km | 2,280 kWh |
| Hyundai Ioniq 5 | 72.6 kWh | 18.1 kWh/100 km | 2,715 kWh |
These figures assume mixed urban and suburban driving typical across Sydney, Melbourne, and Brisbane. Heavier right-foot driving, frequent highway use, or towing will push consumption higher, while a Leaf-style commuter hatchback can dip below 15 kWh per 100 km. Vehicle efficiency therefore shapes whether you need a modest 6.6 kW array upgrade or a substantial expansion.
A useful first step is logging actual driving for two to four weeks, capturing weekday commutes and weekend trips. Most EVs and connected apps report energy used per trip, and the data quickly reveals whether the real-world number sits closer to 15 or 20 kWh per 100 km. This figure, multiplied by expected annual kilometres, gives the kWh your solar system must feed to the car on top of household loads.
Sizing the solar array for combined loads
With the EV energy budget known, the next decision is how many additional panels the roof can host. A standard 6.6 kW rooftop system of about fifteen panels produces 26 to 30 kWh per day in Sydney, Perth, and Adelaide, slightly more in Brisbane, and noticeably less in Hobart or Canberra. A household drawing 20 kWh daily plus 8 kWh for the EV needs closer to 28 kWh of production, which most 6.6 kW systems deliver for eight or nine months a year.
The right sizing depends on more than raw demand, since roof space, shading, and inverter limits all play a role.
Quick sizing considerations:
- Existing array capacity versus combined household plus EV load
- Available unshaded roof area on north, east, and west faces
- Local solar irradiance for your state or territory
- Inverter headroom for an AC-coupled battery or charger upgrade
For many homes in northern states, lifting array size to 10 or 13 kW offers headroom for cloudy weeks and growing household demand. Roof orientation matters here: north-facing surfaces maximise annual yield, while east-west layouts capture morning school-run charging and afternoon return-home windows. The detailed mechanics of array orientation and tilt, covered in this resource on planning a solar installation roof orientation and tilt angle basics, apply equally whether the energy feeds a fridge or a battery on wheels.
Shading from neighbouring trees, neighbouring buildings, or rooftop obstructions can quietly halve output on affected strings. Modern optimisers and microinverters recover significant energy from partially shaded panels and are worth considering when roof space is constrained or trees cannot be trimmed. For households planning to add a second EV within five years, sizing the inverter and switchboard for the larger future load avoids costly switchboard upgrades later.
Inverter selection and battery storage integration
The inverter is the gateway between panels, batteries, the home, and the EV charger. Modern SMA Sunny Boy and Sunny Tripower inverters handle the DC-to-AC conversion for the array, while a separate Sunny Boy Storage unit or hybrid inverter manages battery charging. When the same inverter capacity must feed both household loads and a 7 kW or 22 kW EV wallbox, the system's continuous output rating becomes the limiting factor.
Homes with single-phase power supplies, common across suburban Brisbane and Perth, typically install a 5 kW or 6 kW single-phase inverter that limits simultaneous solar export, battery discharge, and EV charging. Three-phase connections, more common in newer Melbourne estates and parts of Adelaide, comfortably run 11 kW or 22 kW chargers without tripping the inverter. Many owners add an SMA Energy Meter to monitor flows and prioritise charging when export would otherwise be curtailed.
Battery storage adds another layer of flexibility. A 10 to 13 kWh home battery captures midday solar that the house cannot use, then releases it during the evening peak when the EV typically arrives home. Smart energy management systems can also reserve battery capacity for the car's morning departure, ensuring the vehicle leaves fully charged even after a cloudy day. Where net metering rules allow, exporting excess solar during high feed-in tariff windows and importing cheap off-peak energy to charge the EV overnight remains a workable fallback.
Smart charging strategies and time-of-use tariffs
Most Australian distribution network service providers now offer time-of-use tariffs that price evening electricity at premium rates and overnight power at deep discounts. In Victoria, peak window charges on the Victorian Default Offer shift above forty cents per kWh, while off-peak rates fall below twenty cents in many plans. Pairing these tariffs with smart chargers turns overnight grid charging into a low-cost backup that complements daytime solar.
Charger categories worth considering:
- Portable Level 1 units (10 A, 2.4 kW) supplied with most EVs for occasional top-ups
- Level 2 wallboxes at 7 kW single-phase or 22 kW three-phase for routine home charging
- Bi-directional or V2G chargers, currently emerging in trials across South Australia and the ACT
Software-driven schedules can pause EV charging during peak solar production to let the house draw first, then resume after sunset on cheap off-peak power. The result is a hybrid approach where solar handles the bulk of home loads, the battery covers evening demand, and the EV absorbs whatever surplus remains or charges cheaply overnight. For households tracking every kilowatt-hour, regularly reviewing your electricity bill helps verify that expected savings match actual exported and imported energy.
Solar analytics apps from inverter manufacturers expose charging patterns down to the minute. Reviewing this data monthly reveals whether the array is sized correctly, whether the battery is cycling as expected, and whether the EV is genuinely running on sunshine or quietly drawing grid power. Most Australian installers configure these dashboards during commissioning, handing owners a transparent record of where every kilowatt-hour ends up.
Installation, standards, and Australian regulatory realities
A licensed solar and EV charger installer must sign off the work, and systems above 5 kW single-phase require DNSP approval in most states. AS/NZS 5033 governs PV array installation, AS/NZS 4777 covers inverter connection, and AS/NZS 3000 sets the wiring rules any charger must follow. CEC-accredited designers prepare the array layout, while accredited installers handle the grid connection paperwork on the homeowner's behalf.
State-specific rebates and rules shape the final bill. Victoria's Solar Homes Program offers interest-free loans for solar and batteries, Queensland's scheme works similarly, and the ACT Sustainable Household Scheme covers batteries and chargers in one package. NSW, SA, and Tasmania have varying feed-in tariff rates that affect payback calculations, so the same hardware can deliver different returns depending on postcode.
Australian habits also shape outcomes. Many homes install chargers in garages where summer heat derates output, while coastal Sydney and Perth properties need salt-spray-rated hardware. Bushfire-prone regions in Victoria and NSW require elevated mounting and appropriate cable management under AS 3959. Designing around these realities from the start avoids retrofit costs and keeps the system compliant and efficient for its full operating life.
Reach out to an SMA-certified installer for a tailored solar and EV charging design that fits your roof, your driving, and your local tariff. A well-sized system pays for itself faster when every component works together, and the right partner ensures the journey from panels to kilometres goes smoothly. Start with a home energy audit, share your typical driving patterns, and let the data shape a system sized for the kilometres you actually cover.