Fan-On Energy Savings
How the “Fan-On” position can actually save money.
Energy efficiency is an interesting term. Often people associate it with simply using less electricity, but really it’s not about that at all. It’s about effectively converting energy into work. Sacrificing the amount of work performed to save energy is not greater efficiency.
For example, I once lived in an apartment that had an in unit washer and dryer. The dryer was a new “high efficiency” model that claimed to dry your clothes using nearly half the electricity of a standard dryer. Sounds great at first, the problem was that it was only about half the size of a standard dryer and said right on it that it could only handle a half load meaning you would have to run it twice to do a full load. Also it didn’t even do a half load very well. We would often have to run it 2 or even 3 times to get our clothes mostly dry (this was in central Florida so clothes were never fully dry anyway). We and many of the other tenants of the complex complained about the poor quality of these new dryers. The owners said that they would save us money in the long run and we would be grateful for them even if it took a little longer to dry our clothes. But they did not save us money, in fact most saw increased bills. We stopped using ours completely and either went to the Laundromat down the street or attempted to hang dry our clothes (does not work well in central Florida). In the end I learned that using less electricity is not the same thing as increased efficiency.
Sadly In the HVAC industry I see the same problems. Many are so focused on energy savings they forget about comfort. The problem is when people are uncomfortable they are going to adjust the thermostat to whatever is required, for them to be comfortable. At this point the so called “energy savings” disappear.
Here at FanHandler we have found a way to create real energy savings and truly reduce electric bills by making people more comfortable, not less. We have found that these energy savings come from an unlikely place. Ladies and gentlemen, I introduce you to the “Fan On” position.
For years, many have known about the comfort and indoor air quality improvements that come with the constant air circulation of the fan on position. The main problem is that it causes what engineers call a “parasitic use of electricity”. Engineers have concluded that when it comes to using your furnace in the fan on position, the costs outweigh the benefits for most of the population. As a matter of fact there are countless articles written on why you should not use this forbidden “Fan On” position and a lot of math showing just how much electricity and money you are throwing away if you do. And they are right. I am not here to disprove or dispute their findings. However, here at FanHandler we believe that constant air circulation can be done right, and actually save more money than using your system in “Auto”.
You see there is something known as the “fan laws” that has helped us to find the solution.
The fan laws state that if you decrease the speed of the fan by ½ you decrease its energy usage to 1/8. This is pretty well known throughout the industry and many systems are now decreasing the speed the fan speed to 800 or 600 rpm when in the fan on position in an effort to reduce the electricity consumed by the constant blower. This gives significant savings over using the fan at full speed, and has the added benefit of reducing the noise of the constant blower and even making the air filters work slightly better because they are not blasting the germs and dust particles right though the filters. This is a good improvement but, it’s still considered by many to be a waste of electricity. And to some degree they are right. You will not save electricity by running the fan constantly even at 600 rpm. However here at FanHandler we have found that if you continue reducing the speed of the fan there is a switching point where the improved comfort brought by the continuous fan actually outweighs the cost of running the fan.
The Department of Energy's Energy Savers website says that homeowners typically save 3% on their heating bill for every degree that they turn down the thermostat during the winter. In other words this tells us that comfort is a factor in the energy efficiency equation. After all making people comfortable is what furnaces were designed to do in the first place. If we as HVAC professionals can make the home comfortable enough that homeowners don’t need to have the thermostat set as high in the winter, or as low in the summer, then we are saving the home owner money and truly making the whole system more energy efficient.
Constant air circulation has proven to make homes more comfortable. It does this by eliminating the hot and cold spots in homes and keeps an even temperature from room to room and even more importantly, from floor to ceiling. When we put the “comfort factor” in to our calculations, that is the 3% energy saving per degree, it’s easy to see that in real world conditions, constant fan can save a significant amount of energy.
Here at FanHandler we have done real world testing not just laboratory testing to determine that the sweet spot for the fan speed is about 300 RPM. At 300 rpm you are now using only about 1/60th the amount of electricity. With high efficiency ECM blower motors, that's only about 12 to 15 watts. That’s one forth the power consumed by a standard light bulb. We have found that at this speed there are many benefits. Including:
- Completely silent operation (Even standing right outside the air handler you cannot hear that the fan is running).
- Vastly improved air quality(especially for things like UV lights and electronic air cleaners)
- Increased motor life(when the fan never shuts off it’s see significantly less ware from the usual banning on and off).
- And of course energy savings.
Now here is the part you have all been waiting for. The Math(okay so maybe just us engineers have been waiting for this, but here it is anyway).
According to EIA In 2018 the average cost of electricity in the US was around 13 cents per Kilowatt hour. In other words if you were to use 1000 watts for one hour it would cost you 13 cents. So at 15 watts continuous use for a month you would use a total of
15 Watts x 24 Hours x 30 Days = 10800 watts or 10.8 kilowatts costing a total of $1.40 cents.
Now, during the colder months your furnace runs about 30% of the time anyway. So you reduce that figure by 30% giving you an increase on your electric bill of $0.98. That’s less than a dollar a month for using the fan on position at 300rpm.
Now as we have seen from studies and from the reports of our own customers. With continuous air circulation homeowners are just as comfortable at a thermostat setting 3 degrees lower then it was during intermittent operation. Remember there is a savings of 3% per degree so at 3 degrees that is 9% savings on average. The heating bill for a typical home in the US is $200 per month during the heating season. 9% of $200 is $18.00. Minus the $0.98 you have a total savings of $17.02 just for using continuous air circulation.
In addition to that if you factor in higher efficiently of an ECM blower motor during a heating or cooling cycle, and ECM Modulator kit can save a significant mount over a standard PSC setup.
And there you have it. When constant air circulation is done correctly the “Fan On” position can actually use less electricity than “Auto”. And as we have found, in most cases it does.