A solar extractor fan is one of the cheapest, simplest solar buys there is. A small panel drives a fan that pulls hot, stale air out of a shed, summer house, log cabin, garage, chicken coop or dog kennel, with no cable from the house and no running cost. They work brilliantly on hot summer days. They are much less useful against winter damp, and that is where most buying mistakes happen, so this guide explains both.
What a solar fan does well
The beauty of a solar fan is that it runs hardest exactly when you need it most. A shed or coop overheats on a bright, sunny day, and that is when the panel produces the most power. A direct-drive fan speeds up as the sun gets stronger and stops at dusk, with nothing to switch on or maintain.
| Job | Solar fan fit | Why |
|---|---|---|
| Cooling a hot shed, cabin or summer house | Excellent | Heat and sunshine arrive together |
| Venting a chicken coop or kennel in summer | Excellent | Removes heat and ammonia on hot days |
| Clearing fumes from a garage or workshop | Good | Works in daylight while you are working |
| Venting a caravan or horsebox when parked | Good | A roof fan stops it baking in the sun |
| Stopping winter damp and mould | Poor | Little sun in winter, and damp is worst at night |
The three types
Direct-drive kits are a small panel (usually 10-12W) wired straight to a fan. They cost about £20-£25, are very reliable because there is no battery, and run only while the sun is on the panel. This is the right choice for most sheds, greenhouses and coops.
Battery and thermostat kits add a small battery and a temperature switch. The fan turns on when the building gets warm and can carry on for a few hours after sunset. They cost more (about £60) and the battery will eventually need replacing, but they suit animal housing where warm evenings matter.
Roof ventilators have the panel and fan built into one low-profile unit that fits through a hole in the roof. They are neat and weatherproof, and suit caravans, horseboxes, boats and kennels. For campervans with a leisure battery and solar panel, a powered 12V roof fan is a step up again - see our campervan solar guide.
Where they work best
- Sheds and summer houses - stops tools, paint and cushions cooking in July. Pairs well with shed solar power for lights and sockets.
- Garden offices and log cabins - takes the edge off a hot afternoon, though it is no substitute for air conditioning. See garden office solar power.
- Greenhouses - the next step if it still overheats with the vents open. See our solar greenhouse guide.
- Chicken coops - hens cope badly with heat, and a fan clears ammonia. Add a solar coop door and the coop runs itself.
- Kennels, stables and tack rooms - see solar for stables and tack rooms.
Fitting one properly
A fan can only push air out if fresh air can get in. The most common mistake is fitting a fan to a sealed shed, where it just spins without moving much air.
- Fan high, inlet low - fit the fan near the top of the building, where hot air collects, and a vent low down on the opposite side
- Use a vent with a flyscreen so you are not inviting wasps and mice in
- Face the panel south and keep it clear of shade from trees and the house
- Seal around the fan with exterior sealant, and keep the cable run short
- For animals, guard the blades and put the fan where birds and pets cannot reach it
The winter damp problem
Many people buy a solar fan to stop a damp, mouldy shed or garage in winter. It usually disappoints. In December a small panel produces very little, the fan runs for a few hours at most, and condensation forms at night when it is not running at all.
For winter damp, the things that work are passive vents high and low so air moves all the time, a wind-driven turbine vent that spins day and night, fixing any leaks, and keeping the floor off the ground. A cheap hygrometer tells you whether the humidity is actually falling. If you have mains power, a small dehumidifier is the only thing that really dries a building out.
Recommended kit
Everything below was in stock on Amazon UK when this guide was written.
12W solar panel fan kit (direct drive)
The simplest solar fan there is. The panel drives the fan directly, so it speeds up as the day gets hotter and stops at dusk. Ideal for sheds, greenhouses, coops and pet houses. Rated 4.1 stars from over 600 Amazon UK reviews.
amazon Check Price on Amazon →Solar fan with thermostat and battery, 150mm
The fan switches on at the temperature you set, and the battery keeps it running into the evening - the seller quotes about 8 hours on a full charge. Good for animal housing on warm nights. Rated 4.0 stars from 343 reviews. Stock was low when we checked.
amazon Check Price on Amazon →AVT ultra low-profile solar roof ventilator
A neat, self-contained solar vent for caravans, horseboxes, boats, kennels and sheds. It starts extracting within seconds of bright sunlight. The maker is honest that it may not run in winter or dull weather. Rated 4.4 stars, though from only 10 reviews.
amazon Check Price on Amazon →12V caravan roof vent fan, 400mm, with remote
For campervans, caravans and horseboxes with a leisure battery. It runs from 12V, so pair it with a roof solar panel to keep the battery topped up. Measure your roof opening first. Rated 4.2 stars from over 600 reviews.
amazon Check Price on Amazon →12-inch wind-powered turbine vent
Not solar, but the honest answer for winter damp. It spins in even a light breeze, so it keeps air moving at night and through the winter when a solar fan stops. Rated 4.4 stars from 225 reviews.
amazon Check Price on Amazon →Map adjustable air vent with flyscreen, 9 x 6 inch
Fit one low on the opposite side to the fan so fresh air can get in. Without an inlet, an extractor fan moves very little air. Rated 4.5 stars from 466 reviews.
amazon Check Price on Amazon →TempPro TP50 thermometer and hygrometer
A cheap way to see whether your fan or vents are actually bringing the temperature and humidity down. Rated 4.5 stars from over 7,000 reviews.
amazon Check Price on Amazon →Summary
- A direct-drive solar fan (~£24) is the best value for hot sheds, coops and greenhouses
- Choose a battery and thermostat model if it needs to run into the evening
- Roof ventilators suit caravans, horseboxes, boats and kennels
- Always fit a low inlet vent opposite the fan, or it will move little air
- For winter damp, use passive vents, a wind turbine vent or a mains dehumidifier
For more ways to use small solar kits around the garden, see our solar accessories guide and solar shed lights.
Frequently Asked Questions
Do solar extractor fans work?
Yes, on sunny days. A direct-drive fan runs faster as the sun gets stronger, which is when sheds and coops overheat. They do very little on dull winter days or at night.
Will a solar fan stop damp in my shed?
Usually not on its own. Damp is worst in winter and at night, when a solar fan barely runs. Passive vents high and low, a wind turbine vent, fixing leaks or a mains dehumidifier work better.
Do I need a battery for a solar fan?
Not for most uses. A direct-drive fan is simpler and more reliable. Choose a battery and thermostat model if the fan needs to keep running into the evening, for example in animal housing.
Where should I put a solar extractor fan?
High up on the building, where hot air collects, with an inlet vent low down on the opposite side. Put the panel facing south and out of shade.
Can I use a solar fan in a chicken coop?
Yes, it helps on hot days and clears ammonia. Guard the blades, keep it out of reach of the birds, and make sure there is still a draught-free roosting area.