An electric car is usually the single biggest new load a home has taken on in decades, so solar for EV charging needs to be sized around the driving, not just the house. A typical Australian EV uses somewhere near 15 to 20 kWh per 100 km, which for an average commute works out at roughly 5 to 10 kWh a day of extra electricity. That is often the equivalent of adding a second household to the meter, and it changes every part of the design conversation: panel count, inverter size, whether a battery earns its place, and what the switchboard can actually support.
Clean Earth Solar has been designing systems around real usage since 2018, and EV owners are now one of the fastest-growing groups asking for solar panel installation across the Hawkesbury. Here is how sizing actually works when a car is part of the load.
How Much Extra Solar Does an EV Need?
As a working rule, every 100 km of weekly driving adds roughly 15 to 20 kWh of annual-average demand per week, and each 1 kW of rooftop solar in the Sydney basin generates somewhere near 3.5 to 4 kWh a day across the year. Run those two numbers together and a household driving 250 km a week needs in the order of 1.5 to 2 kW of extra panel capacity purely to cover the car.
The reason installers rarely stop at that figure is timing. Solar generation peaks in the middle of the day, and the car is often not home then, so extra capacity is what makes a real overlap possible rather than a theoretical one. The Australian Government’s Green Vehicle Guide publishes energy consumption figures per model, and using the number for the actual car beats using an average.
Start With the Bill, Then Add the Car
A design that works starts with twelve months of billing data and a roof assessment, then layers the vehicle on top as a separate line item. Splitting the two matters because household load and car load behave differently, the house draws in the evening, the car can be told when to draw.
- Annual kWh from the bills, split into daytime and evening use
- Weekly kilometres driven, and the car’s kWh per 100 km
- Usable roof area, orientation and any shading
- Whether a second EV is likely within the next few years
Is Charging an EV With Solar Cheaper Than Charging Overnight?
Charging an EV with solar during daylight uses electricity that would otherwise be exported for a feed-in rate, which is almost always lower than the rate paid to import it back at night. The saving comes from self-consumption, not from generating more.
This is where solar car charging behaviour decides the outcome. A car parked at home on weekdays can soak up the midday peak directly. A car that leaves at seven and returns at six only overlaps with solar on weekends, and that household gets far more out of a battery-buffered setup than out of extra panels alone. Understanding the difference between panel capacity and stored energy helps here, and the guide on kW versus kWh is worth reading before comparing quotes.
Daytime Charging vs Battery-Buffered Charging
Both approaches work. The right one depends entirely on when the car is in the driveway.
Daytime Charging
Best suited to households where someone is home during the day, works from home, or drives shift patterns. A smart charger set to draw only from surplus generation will ramp its current up and down as clouds pass, keeping grid import close to zero. It is the cheapest path to solar for EV charging because no storage hardware is involved.
Battery-Buffered Charging
Best suited to standard commuters. Daytime generation charges the battery, and the battery releases into the car in the evening. It also keeps the house running through an outage, which matters on the semi-rural fringes of the Hawkesbury where supply interruptions are more common than they are in the inner suburbs.
One design detail is easy to miss: a battery sized only for household evening load will be flat well before the car is full. An EV drawing 7 kW will empty a mid-sized battery in a couple of hours, so if the battery is meant to feed the car, it has to be sized for both jobs. The battery sizing guide walks through that calculation, and solar battery installation covers the Sungrow, Tesla Powerwall 3 and Sigenergy options Clean Earth Solar installs.
Solar-Aware Charging Features Worth Asking About
A charger that can see the solar system is what turns a good design into a low bill. Without that visibility, the car charges at full current the moment it is plugged in, pulling from the grid regardless of what the roof is doing.
- Solar tracking or excess-only mode
- Dynamic current adjustment, so charge rate follows generation instead of stopping and starting
- Load management, which throttles the charger when the oven and air conditioner are both running
- Scheduling, to shift any top-up into the cheapest tariff window
- App-level reporting that separates car energy from household energy
Pairing that with real-time solar monitoring gives a clear picture of how much of the car’s charge genuinely came off the roof, the only honest way to check the design is doing what it promised.
Do You Need a Battery as Well?
Not always. A battery is the right call when the car charges after dark, when backup during outages matters, or when household evening use is already high. It is harder to justify when the car is home in daylight and the roof has room for more panels, because extra panels cost less per unit of energy than storage does.
What drives the cost either way is panel count, inverter size, battery capacity, switchboard condition and cable runs, not a headline package price. A hybrid solar system leaves the door open by using a battery-ready inverter now and adding storage later, which suits households buying their first EV and still learning their charging habits.
Single Phase vs Three Phase: What Changes
Phase supply sets the ceiling on both inverter size and charger output, so it is checked before any system is quoted. Most Hawkesbury homes are single phase, and that is workable, it simply caps things.
- Single phase: typically a 5 kW inverter limit per phase under NSW network rules, and a 7 kW single-phase EV charger
- Three phase: larger inverter capacity, and an 11 kW or 22 kW charger becomes possible
- Three phase also allows balanced battery backup across the whole home, using hardware such as the Sungrow SBH range
A 7 kW single-phase charger adds roughly 40 km of range an hour, which covers almost every domestic commute overnight. Faster is rarely the reason to upgrade phases; total system capacity usually is. Where the existing board is old or full, a switchboard upgrade is part of the job, and Clean Earth Solar’s SAA-accredited electricians assess that on site rather than guessing from the street. For why a single phase charger often soaks up more solar than a three phase one, see three phase vs single phase EV charging.
Getting the Order of Work Right
Where solar and a charger are both planned, doing them together is cheaper and cleaner than doing them a year apart, one set of switchboard works, one set of cable runs, one design that accounts for both. For anyone who already has solar, the existing inverter capacity and export limit are the starting point, and EV charger installation can often be added without touching the array at all. Cost drivers for that side of the work are set out in the guide to what affects EV charger installation cost.
Plan the Car and the Roof Together
A system sized for the house alone will disappoint the moment an EV joins it, and a charger installed without reference to the solar design will quietly pull from the grid for years. Clean Earth Solar designs around actual bills, actual kilometres and an actual roof assessment, with every consultation run by a qualified installer rather than a salesperson, no pushy sales, and a lifetime workmanship warranty on the install.
For a solar and EV charger design matched to the car in the driveway, book a free solar assessment or call 1300 753 318. The team will model the numbers for the household, explain what drives the cost, and put a design in writing before anything is committed.
FAQs
How many solar panels do I need to charge an electric car?
For an average 250 km a week, roughly 1.5 to 2 kW of extra solar covers the car on an annual-average basis, which is about four to five modern panels. Most households add more than that so the car can be charged from surplus generation in the middle of the day rather than relying on a perfect match.
Can I charge my EV directly from my solar panels?
Yes. A smart charger with a solar tracking mode will draw only the surplus your home is not using, ramping up and down as generation changes. Charging an EV with solar this way avoids exporting energy at a low feed-in rate and buying it back at a higher one.
Do I need a battery to charge my EV from solar?
Only if the car is usually away during daylight hours. Commuters who plug in at night get far more out of a battery, while households with a car at home during the day can often skip storage and add panels instead.
Will an EV charger work on single phase power?
Yes. A 7 kW single-phase charger is the standard home setup and adds roughly 40 km of range an hour, which is enough for most daily driving. Three phase allows faster charging and a larger solar inverter, but it is not a requirement.
Do I need a switchboard upgrade for an EV charger?
Sometimes. Older boards, boards without spare capacity, and boards missing modern safety switches usually need work before a dedicated charger circuit can be added. A site inspection confirms it either way.
How much does a solar and EV charger setup cost?
It depends on panel count, inverter size, whether a battery is included, the condition of the switchboard and the cable run to the charger. Contact Clean Earth Solar directly for an accurate quote, all pricing is confirmed before any work begins, with no obligation to proceed