7 Best Solar Greenhouse Exhaust Fan Kits (AU) – Off‑Grid 12V/24V Cooling That Works
Hot northerlies can cook a tunnel house by 10 am. If you’re sick of propping doors open and still fighting 40°C air, a solar exhaust system pulls heat out the moment the sun hits the panels—no mains power, no fuss. If you’re building a full setup, see how backyard greenhouse starter systems and advanced greenhouse ventilation tie in.
Quick picks (AU)
- Best Overall: 12V 100W solar fan kit (8–10" metal fan + thermostat) – reliable CFM, simple wiring, runs whenever the sun’s up. Shop 12V 100W solar greenhouse fan kits
- Best Budget: 25–50W compact solar fan set (dual 120mm fans) – keeps hobby tunnels from spiking on mild days. Browse budget solar fan kits
- Best for Beginners: All‑in‑one 30–60W solar roof vent with thermostat – one hole, drop‑in install, tidy look. See all‑in‑one solar roof vents
How to size a solar greenhouse exhaust fan (AU conditions)
Target 1–2 full air exchanges per minute on hot days.
- Volume (m³) = length × width × height
- Required airflow (m³/h) ≈ Volume × 60 to 120
- CFM ≈ m³/h ÷ 1.699
Example: An 8×12 ft (2.4×3.6 m) poly house with 2.1 m peak is ~18.1 m³. At 60 air changes/hr you’ll want ~1086 m³/h (~640 CFM). In sunny Aussie summers, oversize the panel by 25–50% to keep RPM up in light haze. For shade control, pair with shade cloth & blackout systems. For big spans, compare pad & fan cooling.
Comparison table: solar greenhouse exhaust kits (AU)
| Kit | Voltage | Fan size / est. airflow | Panel | Controls | Est. price (AUD) | Best for |
|---|---|---|---|---|---|---|
| 12V 100W metal fan + thermostat kit | 12V | 8–10" / ~500–800 CFM | 100W mono | Thermostat + PWM | $249–$499 | 6×8 to 8×12 houses |
| 25–50W compact dual‑fan kit | 12V | 2×120mm / ~150–250 CFM | 25–50W | Basic temp switch | $99–$199 | Mini greenhouses, seedlings |
| All‑in‑one solar roof vent (thermostat) | 12V | 8–10" / ~400–700 CFM | 30–60W built‑in | Thermostat | $250–$400 | Neat, fast installs |
| 24V high‑CFM shutter fan system | 24V | 250mm / ~900–1200 CFM | 200W+ | MPPT + thermostat | $700–$1,500 | 8×12 to 10×20 tunnels |
| 12V 150mm inline duct system | 12V | 6" inline / ~300–450 CFM | 100–120W | Thermostat + PWM | $300–$600 | Filtered intakes, quieter flow |
7 best solar greenhouse exhaust fan kits in Australia
1) 12V 100W metal exhaust fan + thermostat kit (Best Overall)
Why it stands out: A 100W panel keeps RPM up during peak heat, and an 8–10" metal DC fan moves serious air without needing mains. A snap‑disc thermostat or simple PWM controller prevents over‑cooling in shoulder seasons.
Real‑world use: I’ve run this setup on an 8×12 polycarbonate house in SEQ. With the panel facing true north at ~25–30° tilt, it kicks on by 8:30 am and holds tomatoes under 32°C even on 36°C days—without babysitting.
- Pros: Solid CFM for most hobby houses; easy wiring; scalable with a second intake louvre.
- Cons: Still sunlight‑dependent; needs a proper louvre intake to avoid back‑drafts at night.
Best for: 6×8 to 8×12 greenhouses needing dependable daytime cooling.
Avoid if: You must run at night or in extended cloud cover (consider the Night‑Run bundle below).
12V 100W solar greenhouse fan kits (8–10" fan + thermostat) – ⭐ popular
250mm louvre shutter vents for intake/exhaust
2) 25–50W compact dual‑fan solar kit (Best Budget)
Why it stands out: Two 120mm brushless fans are quiet and sip power—great for seedling frames and compact cold frames where a big cutout would be overkill.
Real‑world use: Ideal on a 6×6 mini house or a lean‑to. I use a simple temp switch at 28–30°C to start one fan, with the second fan bridged to kick in above 34°C.
- Pros: Low cost; easy to mount on polycarbonate; whisper‑level noise.
- Cons: Limited CFM; not enough for full summer on bigger houses.
Best for: Seedlings, propagation tents, compact hobby greenhouses.
Avoid if: You’re in WA/SA summer heat with full‑size tunnels.
Budget 25–50W solar dual‑fan greenhouse kits
3) All‑in‑one 30–60W solar roof vent with thermostat (Best for Beginners)
Why it stands out: The panel and fan are integrated; cut a single circular hole, screw down, and it’s working. Built‑in thermostats make the curve even smoother.
Real‑world use: Great on curved poly tunnels and timber sheds turned into potting rooms. I’ve seen a tidy 4–6°C drop on hot days versus passive venting alone.
- Pros: Easiest install; minimal wiring; clean look.
- Cons: Fixed panel angle; airflow is decent but not as high as a dedicated 10" DC fan.
Best for: First‑time builders who want a neat, fast solution.
Avoid if: You plan to upgrade with larger shutters or multi‑fan arrays later.
All‑in‑one solar roof vent fans (30–60W, with thermostat)
4) 24V high‑CFM shutter fan system (panel + MPPT + battery‑ready)
Why it stands out: Jumping to 24V unlocks higher‑RPM, larger‑diameter fans with proper aluminium shutters—exactly what bigger poly tunnels need. Pair with 200W+ solar and MPPT for stable torque in heat haze.
Real‑world use: On 10×20 polytunnels in NSW Riverina, a 250mm 24V shutter fan with 200–300W of panel holds temps manageable for capsicums when paired with a filtered intake and shade cloth.
- Pros: Serious airflow; shuttered to block back‑drafts; battery‑ready for late‑arvo runs.
- Cons: Higher cost; needs sturdier framing to mount shutters.
Best for: 8×12 to 10×20 tunnels; warm inland regions; heavy summer crops.
Avoid if: You have a small hobby house or can’t mount a shutter frame.
24V 250mm shutter exhaust fans
200W+ 24V solar panel kits
20A MPPT charge controllers (12/24V)
5) 12V 150mm inline duct system (filtered intake + quiet airflow)
Why it stands out: Inline fans let you place the fan out of direct sun and use ducting to pull from the hottest zone. Add a mesh or carbon pre‑filter to keep whitefly and dust down.
Real‑world use: I use a 150mm inline on a seed‑start bay. With a 100–120W panel and PWM speed control, I can trim airflow down on windy days to avoid desiccation.
- Pros: Quieter; flexible placement; easy to add filters and mufflers.
- Cons: Lower static pressure than metal prop fans; filters reduce CFM—oversize the panel.
Best for: Intake filtration, propagation zones, urban dust areas.
Avoid if: You need maximum CFM through thick shutters or long duct runs.
12V 150mm brushless inline duct fans
150mm ducting (insulated or standard)
150mm intake mesh filters
6) Coastal/IP68 brushless 12V metal fan (salt‑air tough)
Why it stands out: IP67–IP68‑rated brushless fans, stainless fasteners and coated housings resist coastal corrosion. Perfect for SEQ and coastal NSW where salt mist eats cheap hardware.
Real‑world use: I’ve replaced rusty budget fans within a year near the beach; this spec pays for itself by surviving the next summer.
- Pros: Weather‑sealed; long life; tolerant of misting overspray.
- Cons: Pricier; slightly noisier at full tilt due to tighter seals.
Best for: Coastal sites, misting‑equipped houses, dusty inland areas.
Avoid if: You’re very price‑sensitive and far from salt or dust.
12V IP68 brushless metal fans (180–200mm)
304 stainless self‑tapping screws
7) Night‑Run off‑grid bundle (battery + MPPT + 8–10" 12V fan)
Why it stands out: Add a LiFePO4 battery and MPPT controller to keep air moving after sundown—handy for residual heat and when humidity spikes at dusk.
Real‑world use: In Adelaide heatwaves, I’ve run a 10" 12V fan for 2–3 hours past sunset using a 100Ah 12V LiFePO4 and 200W panel; plants settle faster and foliar stress drops.
- Pros: Extends cooling window; stabilises RPM under cloud; system‑level resilience.
- Cons: Highest upfront cost; needs fusing and proper cable runs.
Best for: Hot inland climates; dense plantings; fruit set protection.
Avoid if: Daylight‑only operation already meets your temps.
12V 100Ah LiFePO4 batteries
20A MPPT solar charge controllers
8–10" 12V metal exhaust fans
Recommended add‑ons (raise performance and AOV)
- Smart temperature control: DC thermostats or digital temp controllers for hands‑off automation. 12V digital thermostats
- Speed control: PWM controllers to trim airflow on cool days. PWM speed controllers
- Mounting & cabling: Z‑brackets, MC4 extension, inline fuses. Z‑brackets • MC4 extensions • MC4 fuses
Want full climate automation later? See environmental controller systems, or step up cooling with high‑pressure misters or even a ductless mini‑split for year‑round stability.
System builds by greenhouse size (parts list)
6×8 poly house (budget‑minded)
- 25–50W solar dual‑fan kit + 1 intake vent
- Optional: small thermostat switch
- Estimated cost: $120–$220
8×12 polycarbonate (balanced, most popular)
- 12V 100W kit with 8–10" metal fan + thermostat
- 250mm louvre intake opposite the fan
- Optional PWM speed control
- Estimated cost: $300–$600
10×20 tunnel (hot‑zone performer)
- 24V 250mm shutter exhaust + 200–300W solar + 20A MPPT
- Filtered 300×300mm intake louvre
- Optional 24V battery pack for evening cooling
- Estimated cost: $900–$1,600
Planning a full upgrade? Compare turnkey greenhouse packages and polycarbonate greenhouse kits.
Installation tips for Aussie conditions
- Panel tilt and aim: Face true north; ~latitude tilt (25–35° in much of AU). Increase tilt in summer if overheating early.
- Cross‑vent: Put exhaust high on the hot end; intake low on the cool end to sweep air through the canopy.
- Seal and protect: Use butyl tape on polycarbonate; avoid silicone attacking coatings. Stainless hardware near the coast.
- Fuse it: Inline MC4 fuse on positive from panel; separate fuse for battery if fitted.
- Upgrades later: Auto vent openers complement fans nicely—see options inside our ventilation guide.
FAQ: solar greenhouse exhaust fans (AU)
Do I need 12V or 24V?
12V suits 6×8 to 8×12 houses. 24V shines on larger tunnels where higher CFM and longer cable runs matter.
How big should my solar panel be?
Match or exceed the fan’s watt draw by 25–50%. Example: 60W fan → 100W panel for hot Aussie summers.
Will a thermostat help?
Yes—prevents over‑cooling and unnecessary cycling on milder days. Pair with PWM for fine speed control.
Can I run at night?
Yes, with a battery + MPPT controller. A 12V 100Ah LiFePO4 can run a 60W fan for 8–10 hours with headroom.
Shutters or simple vents?
Shutters stop cold night air and pests better. Use louvres for both intake and exhaust if possible.
What about humidity?
Exhaust drops humidity quickly; for precision VPD, add a controller or consider misting for evaporative cooling.
Will it survive coastal salt?
Choose IP‑rated brushless fans, coated housings, and stainless hardware. Rinse salt film from panels occasionally.
Is this enough for mid‑summer heatwaves?
Often, if sized right and paired with shade cloth. For extreme heat, step up to evaporative pad systems.
Wrap‑up
A well‑sized solar exhaust system is the simplest, lowest‑running‑cost way to stabilise a greenhouse in Australian heat. Start with a 12V 100W kit for 8×12 builds or jump to a 24V shuttered system for long poly tunnels—then add thermostats, PWM control and (if needed) a battery to hold temps steady into the evening. For full climate control ideas, explore environmental controllers and our backyard greenhouse system guide.
Compare top solar greenhouse exhaust fan kits (12V/24V) – AU