For anyone, an ideal ceiling fan is one that consumes less energy, moves more air and works quietly.
But finding such a fan is easier said than done.
Fair warning: This article is about finding the most energy-efficient fan from the many ‘right-sized’ choices. The most important metric to look for while buying a ceiling fan is its CFM, so make sure you get a fan with the right CFM, everything else is secondary.
The best way to find an energy-efficient fan is to;
1. Look for ENERGY STAR rating
The ENERGY STAR rating is given by EPA (Energy and Environmental Protection Agency, USA) and every product has to qualify certain strict criteria to be certified. So the easiest way to find an energy-efficient ceiling fan is to check for EPA rating.
Every EPA rated ceiling fan;
- has a minimum CFM of 5000 and an airflow efficiency of 75, at its highest speed.
- has a minimum CFM of 1250 and an airflow efficiency of 155, at its lowest speed.
- can recover the higher price (the cost of energy start fan – the cost of a normal fan) within a reasonable time frame.
An energy star rated fan is 20% more efficient than a normal ceiling fan. So such a fan is definitely going to perform well at the expense of less energy. Unfortunately, not many fans get this certification. So the next best way is to;
2. Find a fan with the best airflow efficiency
Airflow efficiency is the cubic feet of air moved in a minute by the fan per Watt. For eg; if a 40 Watt fan moves 4000 CFM of air its airflow efficiency is 4000/40 = 100.
Note that the airflow efficiency is just a number, it is not expressed in percentages like efficiencies are normally, so don’t be surprised if you see this figure above 100. In fact, the airflow efficiencies of many fans are above 100.
But considering the airflow efficiency rating alone will not give you a good fan. Here is why;
A 20W fan with 2000 CFM has an airflow efficiency of 100. A 53W fan with 4421 CFM has an airflow efficiency of 83. That doesn’t mean the former is the best option for you because you also have to consider how much CFM you need in the first place. Because if you are needing this fan for a covered patio of 300 sq.ft a 2000 CFM fan won’t give you any airflow, you are better off buying the latter low efficient fan.
So the best way to compare airflow efficiency is between fans of the same size and CFM. If there are two fans with the same CFM definitely go for the one with better airflow efficiency.
As per EPA guidelines, all manufactures should provide consumers with an ‘energy information’ data through product catalogs or affixed to the packing. This looks like;
This makes it easy to compare the airflow efficiencies of different ceiling fans without sweating with calculations.
Please note that most brands show these figures only for the highest speed. But some manufacturers also include the CFM and airflow efficiency for different speed settings. But not to worry the airflow efficiency only increases with reduction in speed so the figure you see for the highest speed is probably the least, it won’t go any less.
What is a good airflow efficiency?
Any figure above 75 is good.
What about the number of blades; do more blades mean higher efficiency?
More blades should mean more airflow, right? But that’s not the case. Fan blades push air, as the number of blades increase, the density of air available for the blades to push decreases creating a drag. So more blades don’t mean more CFM. In addition, these blades add more weight to the fan, and considering the drag as well, the fan will need a more powerful motor. So in effect, more blades reduce the airflow efficiency.
Keep in mind that airflow rate and efficiency are just numbers unless you install the right fan in the right place in the right way. The fan you select should be of the right size, should have the right clearances from the sides and above, and also should be at the right height. More information on fan selecting the right ceiling fan size can be found here.
3. Look for a DC ceiling fan
As you know there are DC and AC motors. Compared to an AC motor a DC motor is far more efficient. In fact, a DC fan is 70% more efficient than a normal AC fan. DC fans are also much quieter as well. One downside is they can be more costly.
Most of the DC ceiling fans anyway fall under the ENERGY STAR rating criteria so you don’t have to go looking for a DC fan, just look for those with an energy star rating and you will find some good DC ceiling fans among them.