The cheapest kilometre an electric car travels comes off a home roof, and the most expensive one usually comes from a public DC fast charger on a highway. Everything else sits between those two points. Once the maths is broken down to a cost per kilometre, the gap between charging at home and charging in public stops being a guess and becomes something a household can plan around.
Clean Earth Solar installs home EV chargers across the Hawkesbury and sees the same pattern repeatedly: the charger hardware matters far less to running cost than when, and from where, the electricity comes. This guide sets out the method so any driver can run their own numbers.
What Actually Sets Your EV Charging Cost
Three inputs decide the ev charging cost per kilometre. Change any one of them and the answer moves.
The Price You Pay Per Kilowatt Hour
This is the single biggest lever. A retail electricity plan does not charge one flat rate for most NSW households on a time-of-use tariff; peak, shoulder and off-peak all price the same kilowatt hour differently. Public charging is priced separately again, set by the charging network rather than an electricity retailer, and DC fast charging normally carries the highest rate per kilowatt hour of any option available to a driver.
How Much Energy Your Car Uses Per 100 km
Every EV reports its consumption in kilowatt-hours per 100 kilometres, and it is the number on the dashboard that matters, not the brochure figure. A heavy dual-motor SUV on the M4 in traffic can use close to double the energy of a small hatch on suburban roads. Australian model-by-model consumption figures are published on the Federal Government’s Green Vehicle Guide, which is a reliable starting point before real-world driving data builds up.
Charging Losses You Never See
Not every kilowatt hour drawn from the wall lands in the battery. Some is lost as heat in the cable, the onboard charger and the battery’s thermal management, and slow AC charging on a standard power point loses proportionally more because the car’s supporting systems stay awake longer for the same amount of energy. A 7kW wall charger finishing overnight in a few hours is usually more efficient than a trickle charge that runs for a day and a half.
How Do You Work Out Your Own Cost Per Kilometre?
The formula is short enough to run on a phone, and it beats any generic ev charging cost calculator because it uses the rates on an actual bill.
- Take your car’s real consumption in kWh per 100 km from the trip computer, averaged over a few weeks of normal driving.
- Take the rate you pay for a kilowatt hour in the window you actually charge in, the off-peak rate if you charge overnight, the network’s rate if you use a public charger.
- Multiply the two, then divide by 100. That gives the cost of one kilometre.
- Add roughly ten per cent for charging losses on AC home charging so the figure reflects energy bought, not energy stored.
Run it three times; peak rate, off-peak rate, public network rate, and the size of the gap tends to surprise people more than any single number does.
Why Public Charging Costs More Per Kilometre
Public charging buys speed, and speed is expensive to build. A DC fast charger is serious grid infrastructure with site rental, network demand charges and payment systems behind it, and that cost is recovered through the rate per kilowatt hour.
- Rate tiers: fast DC and ultra-rapid DC are usually priced above slower AC public chargers on the same network.
- Session and idle fees: many networks bill by the minute once charging finishes, so a car left plugged in after it hits 80 per cent keeps costing money.
- Membership plans: some networks discount the per-kilowatt-hour rate for subscribers, which only pays off at high public charging volumes.
None of that makes public charging a bad deal, on a drive down the coast it is the reason the trip works at all. It is simply not the rate anyone wants to pay for the daily commute.
Home EV Charger vs Public Charging for Everyday Driving
For the routine 40 to 60 kilometres a day most Hawkesbury households drive, home charging on an off-peak window is the lower cost per kilometre by a wide margin. The car sits in the driveway for fourteen hours anyway, so charging speed stops being the point, the tariff window is.
Charge Inside the Cheap Window
A dedicated wall charger can be scheduled, either through the charger itself or the car’s own app, so the session starts when off-peak pricing begins. That single setting does more for running cost than any hardware upgrade, and it costs nothing.
The Power Point Is Not a Charging Strategy
A standard 10 amp outlet adds only a handful of kilometres an hour, which means a car with a low battery cannot refill inside a short off-peak window and ends up drawing power at peak rates instead. Slow charging is also where losses stack up. Sizing the charger correctly, and checking whether the switchboard supports it, is covered in our guide to switchboard upgrades for EV chargers, and the installation variables are set out in what drives EV charger installation cost.
Can Solar Make EV Charging Cheaper Again?
Yes, and this is where the cost per kilometre drops furthest. Energy generated by a rooftop system and used in the same moment is not bought from a retailer at all, so solar ev charging replaces the tariff in the calculation with the value of the electricity the household would otherwise have exported.
Daytime Charging Beats Exporting
Feed-in tariffs across NSW have fallen well below the rate paid to import power, so every kilowatt hour sent to the car instead of the grid is worth more to the household. A car home during the day, or a driver who works from home two days a week, can shift a large share of weekly kilometres onto self-consumed solar with nothing more than a scheduling change. Live generation and usage data through a solar monitoring system makes the pattern easy to see.
Batteries Move Sunshine Into the Night
Most drivers are not home at midday, which is exactly the gap a battery closes. Stored solar charges the car overnight at the value of self-consumed generation rather than an evening grid rate. Sizing matters here, because an EV is a substantial nightly load on top of household use, our explainer on kW versus kWh covers the difference between how fast a battery can deliver energy and how much it holds, and solar battery installation walks through the options Clean Earth Solar installs, including Sungrow, Tesla Powerwall 3 and Sigenergy.
Which Charging Mix Suits Your Week?
Most households land on a blend rather than one method. The right blend follows the driving pattern.
- Short daily commute, car home overnight: schedule off-peak home charging, add solar self-consumption on weekends.
- Work from home, car in the driveway during daylight: charge directly from the roof, and only top up from the grid in poor weather.
- High-kilometre driver away all day: a battery is what makes cheap kilometres possible, because the car and the sun are never in the same place at the same time.
- Regular long-distance travel: public fast charging on the trip, home or solar charging for everything else.
A solar system sized around actual usage changes the sums again, because adding an EV to a household lifts annual consumption in a way most systems installed five years ago were never designed for.
Get Your EV Charging Set Up Properly
Clean Earth Solar has been transforming homes with solar since 2018, and every consultation is with an SAA-accredited electrician rather than a salesperson. The team looks at the car, the driving pattern, the switchboard and the roof together, then designs the charging setup around the way the household lives. Get a free quote and find out what the cheapest kilometre looks like at your address.
Ready to charge from your own roof? Talk to Clean Earth Solar on 1300 753 318.
Frequently Asked Questions
How much does it cost to charge an electric car at home?
The cost to charge an electric car at home depends on the tariff in the window the car charges in and how much energy the car uses per 100 kilometres. Charging overnight on an off-peak rate is consistently cheaper per kilometre than charging in the evening peak, and cheaper again when the energy comes from a home solar system.
Is home charging always cheaper than public charging?
For everyday driving, yes. Public DC fast charging is priced to recover the cost of high-powered grid infrastructure, so the rate per kilowatt hour is higher than a household off-peak rate. Public charging still earns its place on long trips where speed is the point.
How much electricity does an EV use?
Most passenger EVs sold in Australia use between the mid-teens and the mid-twenties in kilowatt hours per 100 kilometres, with heavier vehicles at the top of that band. The trip computer figure after a few weeks of driving beats any published number.
Can I charge my EV directly from solar panels?
Yes. A home charger can be set to draw from surplus solar generation, so the car uses energy the household would otherwise export. Charging while the sun is up is the lowest-cost option available, and a battery extends the same benefit to overnight charging.
Do I need a special charger to get off-peak rates?
No, but a dedicated wall charger makes it far easier. Scheduling is built into most home chargers and most EVs, and a 7kW charger can complete a full session inside a typical off-peak window, which a standard power point cannot.