Most homes need an 8–13kW solar system to meaningfully offset ducted air conditioning running costs.
Ducted air conditioning is the biggest single electricity load in most Australian homes. Pairing it with solar means running the system during the day costs you nothing, or close to it, instead of paying full grid rates for every hour of cooling.
This guide covers how to size a solar system for ducted aircon, what affects the equation, and whether adding a battery makes sense for evening cooling.
SolaXs designs and installs solar systems on the Mid North Coast with 25+ years experience. CEC-accredited, local team, premium panels and inverters.
How Much Power Does Ducted Aircon Actually Use
A ducted air conditioning system draws between 3kW and 8kW while running, depending on the size of the unit and how hard it is working. A 14kW cooling capacity system (common for a 4-bedroom home) typically draws 4–5kW from the wall.
The draw is not constant. Inverter ducted systems ramp up and down based on demand.
| Ducted system size | Typical power draw | Daily use (8hrs) | Annual cost (grid) |
|---|---|---|---|
| 10kW (small home) | 2.5–3.5kW | 24–28kWh | $2,400–$2,800 |
| 14kW (medium home) | 4–5kW | 32–40kWh | $3,200–$4,000 |
| 18kW (large home) | 5–7kW | 40–56kWh | $4,000–$5,600 |
| 24kW (very large home) | 7–9kW | 56–72kWh | $5,600–$7,200 |
These figures assume $0.30–$0.35/kWh (typical NSW retail rates per the Australian Government’s energy guidance) and 100 heavy cooling days per year. The Mid North Coast sits in a moderate climate zone, so you might run ducted less intensely than Western Sydney or North Queensland.
What Size Solar System Do You Need for Ducted Aircon
The solar system needs to generate enough power during daylight hours to cover the aircon draw plus your other household usage. If your ducted system draws 4–5kW while running and your base household load is 1–2kW, you need at least 6–7kW of generation happening at the same time.
Panels do not produce their rated output all day. A 6.6kW system might peak at 5.5–6kW around midday but only produce 3–4kW in the morning and afternoon shoulders.
- 6.6kW system – covers a small ducted unit during peak sun hours only, good if the house is well insulated and you have a smaller unit
- 10kW system – the sweet spot for most 3–4 bedroom homes running 14–18kW ducted aircon, covers aircon plus base load from 9am-4pm
- 13kW system – handles large ducted systems (20kW+) and keeps exports flowing even while aircon runs flat out
On the Mid North Coast, a north-facing 10kW system produces roughly 38–42kWh per day in summer (based on Bureau of Meteorology solar exposure averages for the region). That is enough to run a 14kW ducted system for 8 hours and still export surplus to the grid.
Not sure which size suits your home? Our solar system sizing guide walks through how to match system capacity to your actual electricity usage.
Solar Panels Produce Most When You Need Aircon Most
Solar and ducted aircon are a natural match. The hottest part of the day, when your system works hardest, is also when your solar panels produce the most power.
Between 10am and 3pm on a summer day, a well-sized system generates more than enough to cover the aircon load. The excess feeds back to the grid as a credit on your bill.
- Peak solar generation aligns with peak cooling demand
- Inverter ducted systems ramp down as the house reaches temperature, reducing draw below solar output
- Morning pre-cool (8–10am) runs partly on solar, partly on grid
- After 4pm, solar tapers off and the grid picks up the remaining load
- On overcast days, generation drops but so does cooling demand
This natural alignment means you get more value from solar if you have ducted aircon than if you do not.
Reverse Cycle Ducted Systems and Winter Heating
Most ducted systems in Australia are reverse cycle, meaning they heat and cool. Solar offsets heating bills in winter too, not just summer cooling costs.
Winter solar output on the Mid North Coast drops to roughly 20–28kWh per day for a 10kW system. Heating demand tends to peak in the morning and evening rather than midday, so less of it falls within the solar generation window.
- Run heating during the day while panels are generating and let insulation hold warmth into the evening
- A reverse cycle system heating at a coefficient of performance (COP) of 3–4 uses roughly a third of the energy a resistive heater would
- Solar still eliminates daytime heating costs entirely on clear winter days
If you already have ducted reverse cycle aircon and solar, your system is earning its keep year-round.
Pre-Cooling and Zoning to Get More from Solar
Two strategies let you squeeze more cooling out of your solar system and less from the grid.
Pre-cooling means running the aircon hard in the late morning (10am to 12pm) while solar output is climbing. A well-insulated home holds that cooled air for hours, so the system barely cycles during the afternoon peak. You get the benefit of solar-powered cooling without needing the system at full draw all afternoon.
Zone control is the other lever. Most ducted systems let you open and close zones so you only cool the rooms you are using. Closing off spare bedrooms and the lounge during work hours can reduce the system’s draw by roughly 30–50%, depending on the number and size of zones closed.
- Pre-cool to 22–23°C by midday, then let insulation hold the temperature
- Zone off unused rooms during the day to reduce draw
- Use a smart thermostat or timer to schedule cooling within your solar generation window
- Open all zones in the late afternoon only if you have battery backup or are willing to draw from the grid
Combining both strategies, a 6.6kW system can often do the job that would otherwise need a 10kW system.
Should You Add a Battery for Evening Aircon
A solar battery lets you store excess generation from the day and use it to run the aircon after the sun drops. Without a battery, any cooling after 4–5pm comes from the grid at full retail rates.
| Setup | Daytime aircon | Evening aircon | Payback |
|---|---|---|---|
| Solar only (10kW) | Free (solar covers it) | Grid rate ($0.30–$0.35/kWh) | 4–6 years |
| Solar + 10kWh battery | Free | Free until battery depleted (~2–3hrs) | 7–10 years |
| Solar + 15kWh battery | Free | Free for 3–4hrs, then grid | 8–12 years |
Batteries extend the free running window into the evening, but they add significant upfront cost. For most households, solar without a battery pays for itself faster and still eliminates the biggest chunk of aircon costs (daytime running). See our breakdown of how much solar batteries cost for current pricing.
If you work from home and run the aircon primarily during the day, a battery adds less value than for someone who runs it mainly in the evening.
The federal government solar battery rebate can reduce the upfront cost of adding storage, which improves the payback period for evening-heavy households.
Factors That Affect Your Solar and Aircon Match
Solar system size is the headline number, but several other factors determine how well your solar covers ducted aircon costs.
- Roof orientation – north-facing panels produce the most, but east-west splits can spread generation across a wider window
- Insulation and glazing – a well-insulated home holds temperature longer, meaning the aircon cycles less and draws less overall
- Number of zones – if your ducted system has zone control, you can cool occupied rooms only, reducing draw by roughly 30–50%
- Inverter efficiency – premium inverters convert more of your panel output into usable AC power
- Shading – even partial shading on one panel can reduce output across the string, so tree and chimney shading matters
- Feed-in tariff – a higher FIT makes oversizing the system more attractive because excess generation earns more
A site assessment takes all of these into account. The Australian Government’s solar sizing guide gives a starting framework, but it cannot account for your specific roof, shading, and usage patterns the way an on-site inspection can.
Frequently Asked Questions
Can solar panels run ducted air conditioning?
Yes. A properly sized solar system generates enough power to run ducted aircon during daylight hours. Any standard ducted system works with rooftop solar, no special solar-powered air conditioner needed.
How many solar panels do I need for ducted aircon?
A typical 14kW ducted system drawing 4–5kW needs around 20–25 panels (at 400–440W each) to form a 10kW solar system. Smaller ducted units can get by with 15–17 panels in a 6.6kW system.
Is it worth adding a battery just for air conditioning?
It depends on when you run the aircon. If most of your cooling happens during the day, solar alone covers it and a battery adds little. If you cool mainly in the evening, a battery lets you store daytime surplus for after-dark use. Whether adding a battery makes sense depends on your usage pattern and electricity costs.
Can I run ducted aircon off solar at night?
Only with a battery. Solar panels do not generate power at night, so any overnight cooling runs from stored battery energy or the grid. A 10–15kWh battery provides 2–4 hours of evening cooling before it depletes.
Does ducted aircon use more power than split systems?
Yes. A ducted system cooling an entire home draws 3–8kW, while a single split system typically draws 0.5–2kW. However, if you would otherwise run 4–5 split systems to cool the same area, a zoned ducted system can be more efficient overall.
What size inverter do I need for ducted aircon and solar?
Your solar inverter is matched to your panel array, not directly to the aircon. A 10kW solar system typically pairs with a 10kW inverter (or an 8kW unit under the common 33% oversizing allowance). The aircon draws from the grid or solar interchangeably.
How much can solar save on ducted aircon running costs?
A 10kW solar system covering a 14kW ducted unit for 8 hours on a summer day saves roughly $10–$14 per day at NSW grid rates ($0.30–$0.35/kWh). Over 100 heavy cooling days, that is $1,000–$1,400 in avoided electricity costs from aircon alone. For a full picture of installation costs and long-term savings, factor in the rest of your household usage.
Can I add more solar panels later to cover ducted aircon?
Yes. If your current system does not fully cover the aircon draw, adding more panels or upgrading your system is straightforward as long as your inverter and roof have capacity. SolaXs regularly upgrades existing systems on the Mid North Coast to handle new loads like ducted aircon.
Does panel orientation matter for solar and aircon?
North-facing panels produce the highest daily total, but east-west splits spread generation across a wider window. This is useful if you cool from early morning through late afternoon. Your installer can recommend the best orientation for your cooling pattern.
Get Solar Sized for Your Ducted Aircon
SolaXs has been designing and installing solar systems on the Mid North Coast for over 25 years. The team sizes every system based on your actual electricity usage, roof layout, and appliance loads, including ducted air conditioning.
- CEC-accredited installers using premium panels and inverters
- Free site assessment including roof analysis and shading check
- System designed to match your ducted aircon draw and household usage
- Local team, local support, no subcontractors
If you are running ducted aircon and paying high electricity bills through summer, solar is the single most effective way to cut those costs. Contact SolaXs for a free assessment and quote.