Charging an EV with solar in Cairns costs about $1 per 100 km. Charging the same car from the grid costs about $5 to $6 per 100 km. Filling a petrol car costs around $15 for that distance. That one comparison is the whole reason this post exists.
The solar number looks too good, so here is where it comes from. When your panels make more power than your house is using, Ergon pays you a feed-in tariff of 6.006 c/kWh for the power you export. If you push that spare power into your car instead, the only thing you lose is that small credit. So charging from your own roof costs you about 6 cents per kWh, not the 30 to 35 cents you pay to buy power back from the grid.
Quick answer
- An average EV uses about 15 to 18 kWh per 100 km
- Grid charging at 30 to 35 c/kWh costs about $5 to $6 per 100 km
- Charging from your own solar costs about $1 per 100 km
- A typical 40 km Cairns commute needs about 7 kWh a day
- A 6.6 kW system makes that much spare power before lunch
- Add roughly 2 to 3 kW of extra panels for each EV in the driveway
What does it cost to charge an EV per 100 km?
Start with what the car actually uses. An average EV in Australia uses about 15 to 18 kWh of electricity per 100 km. A small hatchback sits at the low end. A heavy dual-motor SUV sits at the high end.
Now put a price on those kWh. On Ergon tariff 11, regional Queensland grid power costs roughly 30 to 35 c/kWh in 2026. So 100 km of grid charging costs about $5 to $6. That already beats petrol by a wide margin.
Solar changes the sum again. Every kWh you send into the car is a kWh you did not export. From 1 July 2026 the regional Queensland feed-in tariff is 6.006 c/kWh, set by the QCA. So 16 or 17 kWh of solar charging costs you about $1 in lost export credit. Not $1 in cash out of your pocket. Just a dollar you would have earned and now will not.
Here is the full comparison over a year of normal driving, 15,000 km:
| How you charge | Cost per 100 km | Cost per year (15,000 km) |
|---|---|---|
| Petrol car, 8 L/100 km at $1.90/L | about $15.20 | about $2,300 |
| EV on Ergon grid power, 30 to 35 c/kWh | about $5 to $6 | about $800 |
| EV on your own solar | about $1 | about $150 |
The petrol row is a standard family car. 15,000 km at 8 L/100 km is 1,200 litres. At $1.90 a litre that is about $2,300 a year, and that is before servicing.
The grid row is already a win. 15,000 km needs roughly 2,500 kWh of charging, which costs about $800 on tariff 11. But the solar row is the one we want you to look at. The same 2,500 kWh costs about $150 in lost feed-in credit. Against petrol, that is a saving of more than $2,100 every year, from panels that were probably going to be on your roof anyway.
If you want to see how those numbers land on your actual power bill, our Cairns electricity bill calculator guide walks through the maths step by step.
How does charging an EV with solar actually work?
You do not need anything exotic. A working solar EV charging setup has three parts.
A smart charger on its own circuit. A proper home EV charger is wired on a dedicated circuit from your switchboard, the same way an oven or air conditioner is. It charges faster and safer than the portable plug-in lead that comes with the car. We install these across Cairns and FNQ, and you can see the units we fit on our EV chargers page.
Solar-tracking mode. This is the clever part. A smart charger can watch what your solar system is producing and what your house is using, then ramp the charging rate up and down to soak up only the excess. Clouds roll over the Tablelands, the charger eases off. Sun comes back, it ramps up. Your car becomes a sponge for spare solar. Sigenstor battery systems even offer an integrated EV charger option, so the battery, inverter and charger work as one unit. You can compare those systems on our battery range page.
Scheduling. If your charger does not have full solar tracking, a simple daytime schedule gets you most of the benefit. Set the charge window for 9 am to 3 pm, when a Cairns roof is producing hard, and most of the power going into the car will be your own. With a Fronius system you can watch this happen live in Solar.web, and our monitoring page shows what that looks like.
The quality of the inverter matters here too, because it is the piece deciding where every kWh flows. As a Fronius Partner Plus dealer we lean on gear that handles FNQ heat and humidity year after year. Our inverter range covers the options.
How many solar panels do you need to charge an EV?
Less than most people expect.
Cairns gets about 5 peak sun hours a day averaged across the year. A 6.6 kW system typically produces somewhere around 26 to 30 kWh a day. An average Cairns commute of 40 km needs about 7 kWh. A 6.6 kW system has made that much spare power before lunch.
The rule of thumb we use when quoting: add roughly 2 to 3 kW of panels per EV for daily commuting. So if a 6.6 kW system covers your house today, a 10 kW system comfortably covers the house plus one EV. For the full sizing method, including how to read your daily usage, see our guide on how many solar panels you need.
On price, the ranges we see in 2026 are about $5,500 to $8,500 installed for a quality 6.6 kW system after rebates, and about $8,500 to $13,000 for 10 kW. We fit SunPower panels, and our Cairns solar pricing guide breaks the costs down.
One local note. The wet season runs November to April, and output drops on grey days. A slightly larger system gives you headroom so the car still charges through a wet week. That is one reason we size residential solar systems for the whole year, not just the dry season.
Do you need three phase power to charge at home?
For most Cairns homes, no.
A single phase home charger delivers up to about 7 kW. That adds roughly 40 to 50 km of range per hour. Plug in when you get home, or set a daytime schedule, and the car is full long before you need it. Home charging is a slow, steady top-up, not a highway fast charge, and 7 kW single phase is plenty for overnight or daytime charging.
Three phase allows faster charging, and it makes sense for some larger homes and sheds. But do not let anyone tell you that you must upgrade your supply just to own an EV. In most cases you do not.
Can you charge your EV at night with solar?
Only if you store the daytime power somewhere, and this is where the battery question comes in.
A 13.5 kWh battery like the Tesla Powerwall 3 holds enough energy for about 80 km of driving. That works, but the battery cycles hard doing it, and most households get more value using the battery to run the house through the evening peak. In practice, most of our EV customers charge the car straight from the sun during the day and let the battery do its normal job. Our Powerwall 3 guide explains how that evening cycle works.
The numbers on batteries have improved a lot this year. A 13.5 kWh battery runs about $12,000 to $16,000 installed before rebates, and the federal Cheaper Home Batteries Program takes roughly 30% off, about $252 per usable kWh for the first 14 kWh under the tiers that started 1 May 2026. Our FNQ battery cost guide has the current figures, and if you are weighing up capacity, read what size solar battery you need first.
If you have no battery and must charge at night, you are simply buying grid power at 30 to 35 c/kWh. Still far cheaper than petrol. Just not the $1 per 100 km headline.
Why install the charger and the solar together?
Because it is one job instead of two.
When we design a solar system and an EV charger at the same time, you get one switchboard visit, one set of cabling, and one design that accounts for everything. The inverter is sized with the charger in mind. The charger circuit goes in while the switchboard is already open. The solar-tracking settings are commissioned on day one. Doing it as two separate jobs months apart means paying twice for site work that could have been done once.
It also means one person is responsible for the whole system. Grant Newman, our owner, is a fifth generation Cairns electrician and SAA accredited, and our team has done this pairing on homes from Port Douglas to the Atherton Tablelands and along the northern beaches. You can see recent installs on our work page, and our 326 Google reviews sit at a 5.0 rating. If cash flow is the sticking point, we offer payment plans through Handypay.
FAQ
How many solar panels does it take to charge an EV?
Roughly 2 to 3 kW of extra panels per EV, which is about 5 to 7 modern panels. A 40 km daily commute needs about 7 kWh, and in Cairns sun that extra capacity produces it easily. A 10 kW system suits a family home with one EV.
Is it cheaper to charge an electric car with solar panels or grid power?
Solar, by a long way. Grid charging costs about $5 to $6 per 100 km on Ergon tariff 11, while charging from your own panels costs about $1 per 100 km, which is just the 6.006 c/kWh feed-in credit you give up. Over 15,000 km a year that is roughly $800 versus $150.
Can I charge my EV overnight from a home battery?
You can, but a 13.5 kWh battery only holds about 80 km of driving, and it earns more keeping your house off the grid through the evening. Most of our customers charge the car from the sun during the day instead. Night charging without a battery just means paying normal grid rates.
Does solar EV charging still work in the wet season?
Yes, though output drops on grey days between November and April. A smart charger in solar-tracking mode takes whatever the roof produces, and the grid quietly covers any gap. Sizing the system a little larger gives you headroom for wet weeks.
Get the numbers for your own driveway
Every roof, commute and car is different, so the honest next step is a quick design based on your actual bill and your actual driving. Send us your details through our contact page and we will put together a free quote for solar, an EV charger, or both in one visit. We are at 32 Magazine Street, Stratford, and we work right across Cairns and Far North Queensland.