About Ceiling Fan CFM Airflow Ratings
DOE requires Ceiling fan manufacturers to test and publish CFM airflow ratings.
Go Back to Part 1: Ceiling fan lighting requirements.
As of January 1, 2009, the EPA requires that ceiling fan manufacturers provide consumers with performance data for most ceiling fans (see Exceptions*). Under FTC rules, an "Energy Information" label must be affixed or printed on the outside of the fan box. This same information must also be published in the manufacturers printed catalogs and on their websites. Online ceiling fan dealers, such as ourselves, must also display this Energy Information on our site. I am proud to say that we have already been providing this information for several years now for fans where the data has been available.
I am a firm believer that the Energy Information label is great for consumers, but it can be misleading or confusing if you do not know how to interpret it. So I have written this article to help clarify some of the important hidden information you can extract from this new data.
*Exceptions: Some ceiling fans are exempt from the federal mandate. Some examples would be fans that have wide palm leaf blades or very large carved blades, or belt driven or rod driven fans such as the Fanimation Punkah. Such fans are considered by the DOE to be for "decorative use only" as they are not designed to produce air movement.
How to interpret the Energy Information label for Ceiling Fans
For clarification, I have placed red letters in the above label that match to the points below.
(A) Testing Speed: The data on the label only reflects results from testing at the "Highest Fan Speed". Because there is no requirement for data at lower speeds, most manufacturers do not test their fans at lower speeds simply because it costs money to run each test. However, there are some manufacturers that do in fact test at all speeds, so in such cases, we publish that data on our website if it is available.
(B) Airflow: Airflow is measured in CFMs (Cubic Feet Per Minute). This is the actual volume of air that the fan is capable of moving on high speed. It is my opinion that this is the most important piece of information for comparing ceiling fans...far more important than comparing efficiency. I will explain this further on in the discussion, but it is important for you to know that the most powerful fans on the market will move around 10,000 CFM, where the average run of the mill fan only moves about 4,000 CFM. You will find a dramatic difference in your level of comfort when sitting beneath the two fans.
(C) Electricity Use: The amount of electricity a fan uses is measured in Watts, so you can easily compare the power a fan uses to that of a light bulb. If you pay close attention to this number as you compare fans, you will find that even the most energy guzzling ceiling fans rarely use more than 100 Watts. On average, a decent fan will use somewhere around 65 to 75 watts. Keep in mind that this number does not reflect the wattage of any light fixture that comes with or gets added to your fan. This is a very important consideration, because a light fixture can use 2 or 3 times as much electricity as the motor. In the past, some light fixtures used as much as 300Watts, which completely throws the overall efficiency off of even the most energy efficient fan motor. The current legislation requires fan lights to be less than 190 watts, but again, most fan motors use only about 70 watts without lights. Add on a 190Watt light fixture and you are now using 260Watts when you turn the fan and light on at the same time. In many cases, you can remedy this by either purchasing a light fixture that uses CFL bulbs, or one that will accept them. Read more about the legislation for Ceiling Fan Lights here!
(D) Efficiency: Ceiling fan efficiency (as defined by the EPA) is measured by dividing the CFMs produced by the Watts the fan consumes. Although the number generated from doing this math provides an additional method to compare ceiling fans, I do not recommend comparing fans solely based on this data because it can be misleading. This is not a traditional efficiency rating between 1% and 100%. In fact, it is not a percentage at all. It is purely a ratio of the CFMs to Watts, so it is possible for the number to be well over 100. In fact, you will find in the statement below that the range is anywhere from 51 to 176 depending on the size of the fan. Although a higher number is desirable, fans with a very high Airflow rating (CFMs) that have an average efficiency rating may in fact be the better choice. This is the main point of this article, which I explain in more detail further on.
(E) Compare: Notice the note beneath the actual data that states "Compare: 49" to 60" ceiling fans have airflow efficiencies ranging from approximately 51 to 176 cubic feet per minute per watt at high speed." For fans that are less than 49" the note will read "Compare: 36" to 48" ceiling fans have airflow efficiencies ranging from approximately 71 to 86 cubic feet per minute per watt at high speed." This bit of information is telling you what the expected range of efficiency should be for the size of fan you are considering. With larger fans, you will notice a wide discrepancy between the numbers 51 and 176. Again, this is not a percentage efficiency, it is a ratio that you can use to calculate how much it might cost you to operate the fan and get the CFMs that are most necessary to cool you off. Ultimately, a very high CFM rating with a very high efficiency rating is the best of both worlds. But, in order to get the highest CFMs, most fans must use more power, so they will run slightly lower in the efficiency ratio than less powerful models.
(F) Energy Saving Tip: The note suggesting that you turn your ceiling fan off when you are not in your room is a requirement on the label. This makes good sense because a ceiling fan does not lower the temperature in a room, it only provides comfort by creating a "wind chill" effect when you are near it. So, unless you have animals that roam the house and you are concerned about their comfort, in most cases it is a good idea to turn a fan off when you are not in that room. However, there are some exceptions. For example, you might have a fan in a room with a window open, and you like to use it to circulate fresh air into the house. This can impact other rooms that do not have a fan or window, so you might find it more comfortable with that particular fan left on even if you are not in the room.
Airflow - vs - Wattage - vs - Efficiency...which is most important?
This is where we start to get serious and analyze the information that is on this label
The label does not tell you which of the 3 specifications is most important, nor does it offer information on how to make the best evaluation. But, the good news is that it does give you the necessary information for you to figure out what is best for you and your particular needs or desires...if you know what to look for.
As mentioned previously, it is my opinion that the Airflow (or CFM) is by far the most important bit of info. The truth is, the range of energy consumption between 52" ceiling fans that use the least electricity and the most electricity is roughly 30 to 110 watts. Now that might sound like a big difference at first because mathematically, it says that the most energy guzzling fans use more than 3 times as much electricity as the least energy consuming fans. But when you look closer at the overall cost of operating either fan on an annual basis, the lack of airflow produced by a fan that is less powerful is by no means compensated by the energy savings.
Here's the math
For this example I am going to assume that both fans are operated 200 days/year 8 hours/day which comes out to 1,600 hours
Fan A uses 30Watts (=.03 kWh)
Fan B uses 110Watts (=.110 kWh)
Cost of Electricity $.10/kWh (national average published by EPA)
Fan A = .03 kWh x $.10/kWh x 1,600 h = $4.80 per year
Fan B = .10 kWh x $.10/kWh x 1,600 h = $16.00 per year
Total savings using Fan A instead of Fan B = $11.20/year
So, by using the cheapest fan with the smallest motor that moves almost no air, you save a whopping $11.20/year...but, you do not feel cool because your fan does not have enough power to cool you off...which basically translates into a wasted $4.80/year rather than a savings of $11.20/year.
Here's the real kicker
In the past, the EPA published information stating that if you use ceiling fans throughout your home, you can lower your thermostat by as much as 10 degrees without compromising your level of comfort, resulting in an actual savings of as much as 40% off your cooling bill. Other reports suggest that every degree you raise your thermostat will save you about 7% on your air conditioning cost.
The problem with making energy saving calculations is that the price people pay for air conditioning varies so dramatically based on the configuration of their system, the efficiency of it, and how cool the house must be in order for one to feel comfortable are all variables that vary dramatically from one home to the next. But, I will suffice to say that at a minimum, with say 5 high powered energy guzzling ceiling fans in a home where the cost of air conditioning runs say just $150.00/month, you should be able to save 15% of that with the powerful ceiling fans. So here's the math that makes the kicker:
Lets see how much it costs to operate 5 ceiling fans per month at 8 hrs/day
5 Fan A models x 30 days x 8 hrs x .03 kWh x $.10/kWh = $3.60/mo
5 Fan B models x 30 days x 8 hrs x .10 kWh x $.10/kWh = $12.00/mo
Some studies show that many people who own ceiling fans do not actually lower their thermostat and end up spending more money. In my experience, there are people who own ceiling fans that do not move enough air to change their comfort level. Such fans are commonly sold at home centers and the like...and normally sell for less than $150.00. So, in this case, we are not going to change our thermostat with the energy saving fan model, so we end up spending an extra $3.60/month and do not save anything on our air conditioning bill.
Now, lets see how much we can save if we lower our thermostat by 10 degrees and use the powerful fans
Normal air conditioning cost = $150.00
Say you save only 15% ($150 x .60) = $60.00 in savings
Minus cost of operating fans = $60.00 - $12.00 = $48.00
So, there you have it....the rational for using less efficient, more powerful ceiling fans can make a lot of sense. Keep in mind that the numbers above could be half or double what may happen in your home, but in either case, the numbers still make sense.
Bottom line: My suggestion when looking at the new Energy Information specifications as mandated by the EPA is to first consider finding fans you like that have the highest CFM rating possible in the price range you can afford. If you find several ceiling fan models that you like, and they all have similar CFM ratings...then compare the Efficiency rating to help make your final decision.
Factor in your own air conditioning costs and quantity of fans and you will see that Doing so can possibly save up to 40% on your cooling bills.
The EPA actually has developed a calculator that shows the energy savings of an "EnergyStar" ceiling fan compared to a "Conventional" ceiling fan. Although I have no idea what fans they are actually comparing, I like to use their data for this example. Their calculator determines that the EnergyStar model will cost about $17/year to operate while the "Conventional" fan costs around $36/year. That is if you operate the fans at High Speed whenever they are on.
Go Back to Part 1: Ceiling fan lighting requirements.
Useful Resources:
http://www1.eere.energy.gov/buildings/appliance_standards/residential/ceiling_fans.html
http://www.americanlightingassoc.com/members/files/CeilingFanInfo_9-08.pdf