Be cautious. Attic fans – either solar or electric – are not as effective at cooling overheated attics as manufacturers claim.
You may be tempted to use attic fans because they are inexpensive compared to other alternatives, or because they are easy to install.
But attic fans can be very ineffective or even counterproductive. They only should be used as a last resource, in overheated attics.
Alternatives to attic fans
But there is only one very effective way of solving thermal problems associated with overheated attics: airtight attics (to avoid hot air to escape to the living space) with very high levels of insulation (to avoid heat transfer through the materials that make up the ceiling).
do never use Attic Fans in poorly sealed attics
Do not ever use attic fans - either electric or solar - in poorly sealed attics. Fans will draw air from the rooms below, increasing your cooling bills instead of lowering them.
Sealing is also crucial to prevent back-drafting and moisture problems.
Also consider carefully your attic ventilation, before installing any fan. See if the roof vents aren't blocked and are large enough.
Solar vs. Electric attic fans
Solar powered fans are based on a small photovoltaic solar panel powering a small motor. Their capacity ranges from 800 to 1200 CFM (Cubic Feet per Minute), which is less than the capacity of many electric fans.
Since they operate without fuel, they can save you some money; and since attic overheating periods coincide with high solar resources, their capacity is not affected during the periods when the fans are most needed.
Another significant advantage over electric fans is that they not require wiring, which makes them a lot easier to install.
In some models, their solar panel is mounted separately, using a bracket to allow the panel to be tilted toward the sun as squarely as possible.
Prices & Warranties
The best solar attic fans are more expensive than electric units.
Electric fans can cost you, online, $50-$100, while solar units prices are in the range $200-$300+.
Electric attic fans vs. Solar powered attic fans
Electric attic fans are more powerful and cheaper than solar attic fans, but they consume a lot of power. If you do choose to use an electric attic fan, consider one with a thermostat (an almost standard feature) and set it for 130ºF or above. This will reduce electricity consumption…
They also have a small warranty (often 1 year for parts), when compared to new solar units: some solar attic manufacturers are offering a 25-year warranty on solar panels, fan housings and motors.