These “Vari-Cyclone” ceiling fans from FanWorks are perhaps the most efficient ceiling fans available. The fans utilize what Fanworks calls “Gossamer Wind” blade design technology, which is said to deliver 40% more air flow without any increase in power use. They also run on DC power, which also adds to their efficiency when off-grid power is used.
On the advantages of running under DC power, Fanworks says:
The average AC-powered ceiling fan draws between 0.5 and 1 amp. When an inverter is used to run the AC ceiling fan, you are pulling 5 to 10 amps DC to run the fan. This does not include the power consumed by the inverter to produce the AC power required by the ceiling fan.
The Vari-Cyclone, DC-powered ceiling fan, runs directly from your battery bank, no inverter required, and draws only 0.5 amp @ 12 VDC, making the Vari-Cyclone 10 times more energy efficient than an AC-powered ceiling fan.
Here are some stats:
Power Consumption: (with 3-blade configuration):
At 12 volt: 60 rpm, 7 watts, 2500 cfm.
At 24 volt: 120 rpm, 27 watts, 3400 cfm.
You can see a very in-depth analysis of the performance of these fans here.
Available from: Survival Unlimited ($175-$195)