Yes, solar can run your air con. A properly sized system runs your air conditioning through the day for close to nothing, and if you add a battery it runs through the night as well. Air con is the single biggest line on a Cairns power bill, and it is the number one reason locals call us about residential solar.
We install solar every week across Cairns, Port Douglas, the northern beaches and the Atherton Tablelands. Almost every job starts with the same complaint: the summer bill. This guide shows you exactly what air con draws, what that costs on the grid, and what size system fixes it before summer 2026-27 arrives.
Quick answer
- A large split system draws about 1.5 to 2.5 kW while running. A 6.6 kW solar system makes far more than that on a sunny FNQ day.
- Running one large split 8 hours a day on grid power costs about $150 a month. Solar cuts the daytime share of that to near zero.
- A 6.6 kW system covers daytime cooling for one or two splits plus the rest of the house.
- A 10 kW system suits ducted air con or three or more splits.
- Night cooling needs a battery. A 10 to 13.5 kWh battery runs a large split all night with room to spare.
- Air con demand peaks on hot sunny afternoons, which is exactly when solar output peaks. The two fit together better here than almost anywhere in Australia.
What does an air conditioner actually draw?
Here is what typical units pull while they are running, not just at startup:
- Small split system (bedroom size, 2.5 kW cooling capacity): about 0.8 to 1.2 kW of electrical draw.
- Large split system (living room size, 7 to 9 kW cooling capacity): about 1.5 to 2.5 kW.
- Ducted system: about 3 to 8 kW depending on how many zones are open.
Two things soften those numbers in real life. Modern inverter splits ramp down once the room hits temperature, so a unit rated at 2 kW might average 1.2 to 1.5 kW over an afternoon. And you rarely run every zone of a ducted system at once. But in a Cairns January, with 33 degrees outside and 80 percent humidity, your units work hard for long stretches. Size for that, not for a mild day.
What does air con cost on grid power?
Regional Queensland grid power costs roughly 30 to 35 cents per kWh on Ergon tariff 11. Take a large split averaging 2 kW, running 8 hours a day, at 32 cents:
2 kW x 8 hours x $0.32 = about $5 a day. That is about $150 a month, for one unit.
Add a second split in the bedrooms, a pool pump and the usual household load, and you can see how Cairns summer bills hit $1,000 plus a quarter. Ducted systems are worse. A ducted unit pulling 5 kW for those same 8 hours costs about $12.80 a day, close to $390 a month.
If you want to check your own numbers, our Cairns electricity bill calculator guide walks through how to pull your usage from your Ergon bill and work out where the money goes. For most FNQ homes, cooling is half the summer bill or more.
Why air con and solar are a perfect match in the tropics
Some appliances fight against solar. An oven at 7 pm runs after the sun is gone. Air con in FNQ is the opposite case.
Your cooling demand peaks on hot, sunny afternoons. That is exactly when your panels produce the most. The hotter and sunnier the day, the more you want the air con on, and the more free power is sitting on your roof. Cairns gets about 5 peak sun hours a day averaged over the year, and summer afternoons deliver the strongest production of all.
This matters because of how the sums work in regional Queensland now. The feed-in tariff is 6.006 cents per kWh from 1 July 2026. Grid power costs 30 to 35 cents. So every kWh you use yourself is worth roughly five times what you get for exporting it. Running your air con on your own solar is one of the best uses of a panel there is. We cover this self-consumption maths in more depth in our guide to solar power for Cairns homes.
How many solar panels do I need to run my air con?
You do not size a system for the air con alone. You size it for the air con plus everything else the house runs during the day. Here is how we scope it for FNQ homes:
A 6.6 kW system covers daytime cooling for one or two split systems plus the normal house load. On a sunny afternoon it can produce 4 to 5 kW, which handles a large split, a small split, the fridge, the pool pump and more at the same time. Averaged over the year it makes roughly 26 to 30 kWh a day. Installed, a quality 6.6 kW system runs about $5,500 to $8,500 after rebates. Our 2026 Cairns solar pricing guide breaks down what drives the price within that range.
A 10 kW system suits ducted air con or three or more splits. Ducted units can draw 3 to 8 kW on their own, so you need the extra headroom to cool the house and still cover the rest of your load. Expect about $8,500 to $13,000 installed.
One rule we push hard with every customer: size for summer, not for the yearly average. A system that looks generous in July can fall short in January when the ducted unit runs 10 hours a day. If you want to work through the panel maths for your own roof, our new guide on how many solar panels you need goes step by step.
We install SunPower panels paired with Fronius inverters. We are a Fronius Partner Plus dealer, which matters in the tropics because the inverter cops the heat and humidity for 10 plus years. You can see recent local installs on our work page.
The pre-cooling trick every FNQ solar owner should use
This is the single best habit for running air con on solar, and it costs nothing.
Run your air con hard from about 1 pm to 5 pm, while your panels are pumping. Set it a degree or two cooler than you normally would. Chill the whole house, walls and all, on free solar power. Then ease the setpoint back in the evening.
A pre-cooled house holds its temperature into the night, so the air con works far less during the expensive after-dark hours. Instead of the unit grinding away at full draw from 6 pm on grid power, it just tops up a house that is already cool. Families we install for tell us this one habit changed their evening usage more than anything else.
Timers make it automatic. Set the air con to start at 1 pm before you leave for school pickup. If you have a Fronius inverter, our guide to Fronius Solar.web monitoring shows you how to watch your production live and line your cooling up with it. We can also set up consumption monitoring so you see exactly what the air con draws against what the roof makes.
Can solar run my air con at night?
Not on its own. Panels stop producing at sunset, and FNQ nights in the buildup are hot and sticky. Night cooling needs a battery.
The numbers work like this. A large split averaging 1.5 kW for 8 hours overnight uses about 8 to 12 kWh. A 10 to 13.5 kWh battery covers that with room to spare for the fridge and fans. We install Tesla Powerwall 3, BYD, Sigenstor and Fronius batteries, and the Powerwall 3 in particular pairs well with big cooling loads.
Timing is on your side here. The federal Cheaper Home Batteries Program takes about 30 percent off an installed battery, tiered from 1 May 2026 at about $252 per usable kWh for the first 14 kWh. A 13.5 kWh battery that costs $12,000 to $16,000 before the rebate comes down materially. Our FNQ battery cost guide has the full pricing picture, and the QLD battery rebate guide shows how to claim it in Cairns. If you are unsure how big to go, start with what size solar battery you need.
Does the wet season ruin this plan?
No, and the timing is kinder than people expect. The wet season runs November to April, and cloudy days do cut solar output. But look at when you actually need cooling most: the humid buildup from October to December. Those are the months locals call the sweatiest of the year, and they come with plenty of sun between storms. Your worst cooling weeks and your best production weeks overlap heavily.
Deep in the wet, in February and March, you get more heavy cloud. Output drops on those days but rarely to zero, and the air is often cooler under rain anyway. We cover the detail in our guide to solar output on cloudy days.
Worked example: two splits, three setups
Here is a typical Cairns household in summer. Two splits, one large in the living area and one small in the bedrooms, running about 8 hours a day, plus normal house load. Grid power at 32 cents. Figures are rounded and exclude the daily supply charge, which you pay in every case.
| Grid only | With 6.6 kW solar | With 10 kW solar + 13.5 kWh battery | |
|---|---|---|---|
| Daytime cooling (1 pm to 9 pm splits) | All grid power | Covered by solar until sunset | Covered by solar |
| Night cooling | Grid power | Grid power | Covered by battery |
| Grid power bought per summer day | About 26 kWh | About 9 to 11 kWh | About 1 to 3 kWh |
| Rough summer cost per day | About $8.30 | About $3.00 to $3.50 | Under $1, before export credits |
| Rough summer quarter | $750 plus | About $270 to $320 | Under $100 |
The 6.6 kW setup roughly cuts the summer bill by more than half. The 10 kW plus battery setup nearly removes it. Every house is different, which is why we quote from your actual Ergon bill, not from a template.
FAQ
Can a 6.6 kW solar system run air conditioning?
Yes, comfortably during daylight. A 6.6 kW system produces 4 to 5 kW on a sunny afternoon, which covers one or two split systems plus the rest of the house. It does not cover night running, which needs a battery or grid power.
How many solar panels do I need to run a ducted air conditioner?
Ducted systems draw 3 to 8 kW depending on zones, so we recommend a 10 kW solar system, which is around 22 to 24 modern panels. That gives you enough afternoon output to run ducted cooling and the rest of the home at once.
Is it free to run air con on solar during the day?
Close to it. Power you use from your own roof costs you nothing to generate, and you only give up the 6.006 cent feed-in credit you would have earned by exporting it. Compared with buying that power at 30 to 35 cents from the grid, daytime cooling on solar is about 80 percent cheaper.
Does air con on solar still make sense with the low feed-in tariff?
Yes, more than ever. The low tariff punishes exporting, not solar itself. Air con lets you use your production on the spot, which is worth roughly five times the export rate. High daytime users like air conditioned FNQ homes get the best returns from solar. Our post on whether solar is worth it in Queensland runs the full numbers.
Get sized before summer
We are G-Solar & Electrical, based at 32 Magazine Street in Stratford. Grant Newman, our owner, is a fifth generation Cairns electrician, SAA accredited, and we have 326 Google reviews at a 5.0 rating from homes across FNQ. If the upfront cost is the hurdle, we offer payment plans through Handypay.
Summer 2026-27 is close, and install calendars fill fast once the heat arrives. Send us your latest power bill and request a free quote. We will size a system around your air con, your roof and your family, and show you the numbers before you spend a cent.