Energy Saver 3000 and other PFC nonsensePosted on March 6th, 2010 6 comments
My friend Jack recently asked me to write about the Energy Saver 3000 and whether it will save money on your electricity bill. I saw this product advertised on TV about a year ago and nearly fell out of my chair when I heard the ridiculous claims being made about saving money using a power factor correction device. And I understand other charlatans have jumped on the bandwagon and have begun offering similar devices that are supposed to ‘pay for themselves in a few months’ with the money you will save on your electricity bill.
Few people understand what power factor means and I guess this makes it an ideal way to extract money from consumers who trust that anything that appears on a TV ad must be legitimate. Basically, the power factor is an indication of phase alignment of the voltage and current in an AC waveform. In a purely resistive load, the alignment is perfect, which gives it a power factor of 1. On loads that have energy storage elements in them like inductors and capacitors, it can get out of alignment and the power factor falls below 1. A power factor below 1 doesn’t mean that all the energy is getting lost, it’s just that a portion of it is being returned to its source. Whenever energy is transmitted through wires a small amount of it is lost in the resistance of the wires, so it’s preferable to minimize the amount that gets returned. The power company has a vested interest in keeping the power factor as close to 1 as possible for the same reason. However, unless you’re a commercial customer, you don’t get charged for power that is returning to its source. You only get charged for actual power consumed. And in the grand scheme of things, the amount being returned is rather small as a percentage of the overall total, less than 10% for the average household. Since about 7% of all power is lost in the power company’s transmission lines, the overall loss due to having an imperfect power factor is 10% x 7% = .7%. This means that if every household in the nation were to have a PFC device (one that actually worked) the maximum potential energy savings is .7%.
You can improve the power factor of an inductive load such as a motor by adding a properly sized capacitor to it. This is what these power factor correction devices claim to do. But the problem is that they can’t match the capacitance to the load because most of these motors run only intermittently and so when they are not running, the capacitor will cause the power factor to become out of phase in the opposite direction. And none of these devices has active monitoring to switch the capacitor in and out. That is why these devices simply cannot save energy. Even if they did actively monitor and correct the power factor, the savings would be nowhere near what they claim since, as mentioned, the average savings would only approach .7%.
The Energy Star website has an interesting entry on these devices:
“ENERGY STAR does not qualify any Power Factor Correction Devices. Please send us an email at email@example.com if you see one that claims to be ENERGY STAR certified.
Power Factor Correction Devices claim to reduce residential energy bills and to prolong the productive life cycles of motors and appliances by reducing the reactive power (kVAR) that is needed from the electric utility.
We have not seen any data that proves these types of products for residential use accomplish what they claim. Power factor correction devices improve power quality but do not generally improve energy efficiency (meaning they won’t reduce your energy bill). There are several reasons why their energy efficiency claims could be exaggerated. First, residential customers are not charged for KVA-hour usage, but by kilowatt-hour usage. This means that any savings in energy demand will not directly result in lowering a residential user’s utility bill. Second, the only potential for real power savings would occur if the product were only put in the circuit while a reactive load (such as a motor) were running, and taken out of the circuit when the motor is not running. This is impractical, given that there are several motors in a typical home that can come on at any time (refrigerator, air conditioner, HVAC blower, vacuum cleaner, etc.), but the unit itself is intended for permanent, unattended connection near the house breaker panel.
For commercial facilities, power factor correction will rarely be cost-effective based on energy savings alone. The bulk of cost savings power factor correction can offer is in the form of avoided utility charges for low power factor. Energy savings are usually below 1% and always below 3% of load, the higher percentage occurring where motors are a large fraction of the overall load of a facility. Energy savings alone do not make an installation cost effective.
Power factor correction devices are NOT eligible for a federal tax credit.”
Most of the ‘evidence’ to support claims by companies hawking these devices is very unscientific, often times just unsupportable anecdotes by shills talking about how their energy bill went down after installing one of them. This could simply be due to behavioral changes one naturally makes when focusing on an area of improvement, behavior that a customer who purchases an expensive power saving device is likely to engage in without realizing it. To truly measure improvement, you need to run a controlled experiment and I’ve yet to see a legitimate experiment demonstrated when it comes to these devices. Even the videos on the websites don’t bother to measure actual power, just current or power factor before and after which to me means that they are intentionally trying to mislead customers. There are many inexpensive power meters out there such as Kill-A-Watt and yet there are no demos with a power meter used properly, i.e., showing watts consumed before and after installing a PFC device. Instead, they show power factor or current before and after, which makes for an impressive demo, but tells you nothing about the energy savings you’d experience.
If you’re thinking about buying one of these devices, I’d recommend you buy a whole house energy monitor like the TED5000 instead. It will cost less than a useless PFC device and is likely to help you figure out where your energy is going so you will be more aware of how you can save energy. It will also tell you exactly what your power factor is at any moment. As I type this, my furnace blower (a 900W load) is running and my power factor is .94, which is close enough to 1 that it’s hardly worth worrying about.
6 responses to “Energy Saver 3000 and other PFC nonsense”
George Shaw March 22nd, 2010 at 09:19
Lee, do you know anything about the Watt Wizard that was sold many years ago? Based on a NASA patent, as I recall, it claimed to be an active power factor controller that was placed in series with a motor, say on refrigerator, and step-wise reduced the voltage to the motor when the load was light. I had one on my refrigerator and could hear the motor noise reduce in steps several seconds after the motor would start. There is what may be a similar product on the market now called the Green Plug.
I did a quick search and found that the Watt Wizard appeared in a full page ad in Popular Mechanics in 1980. It is based on a 1976 (now expired) NASA patent (#4052648) and is intended to correct the power factor on an induction motor. Based on the patent description, it is a much more sophisticated approach than just inserting a capacitor across the power line which is what these whole-house power factor correction devices do. The intent of the Watt Wizard is to correct the power factor in induction motors that are not matched to the load, such as when they are used to drive a variable load. This device would have a much better chance of saving energy than the whole house PFC device since it actually measures current and phase and thus could correct the power factor in real time. I don’t know if a refrigerator’s motor load varies much over time since it’s driving the compressor and you’d think that the engineers who design modern refrigerators would take great care in matching the motor to its load to maximize overall efficiency.
It mentions in the ad that it can save ‘up to 50% of energy on lightly loaded or unloaded motors’ and around ’5% to 7% on fully loaded motors’. Those claims seem reasonable to me. The cost of this device back in 1980 was around $40 which is about $100 today. If your refrigerator draws 130W on average, or 94 KWh per month, like mine does, and this device could save 10% of its energy, then it would pay for itself in 9 years. I assumed that a modern version would cost $100 and a kWh cost $.010, which is the U.S. national average.
The Watt Wizard is not a magical solution, but the claims in the ad are not too misleading, if you read between the lines. It’s not that difficult to do PFC today. In fact, in Europe, computing equipment that draws more than 75W watts has been required to have PFC since 2001. When I worked for HP we used to pay about $1 extra on a $15 power supply to get a model with built-in PFC. In the case of computing equipment, it isn’t done so much for increased efficiency, but rather to reduce the harmonics that are put back on the power mains when using switching supplies.
Dave Flad April 30th, 2010 at 07:55
Lee, I fell into the “sales pitch” related to the whole house PF correction devices, and for the reasons you mentioned.
Now, in defense of my apparent ignorance, I do have to ask you about your statement that we “do not pay for power that is returned”. The electric company meter that measures my consumption only goes forward, spinning UP the apparent kilowatt consumption.
So if the power consumption is out of phase (the current and voltage sine waves are skewed along the x-axis), this is occuring AFTER the meter has already acknowledged that we took it from the grid, right?
It was/is my understanding that while not an optimal approach, these devices do provide some relevant correction to the synchronization of the power and voltage curves — reducing the power required by the end devices, or at least helping it to be more efficiently consumed(i.e. less wasted power and less heat as a result increasing lifespan). Please correct me if I’m out in far left field on this.
Last data point — I have noted a decrease in my utility bills after putting one in. It’s not the phenomenal claims of 25% savings or such, but it was definitely noticeable. I won’t get my ROI for another year, but it’s a few dollars back into my pocket each month anyway — inefficient as it might be based on your comments.
It’s good to hear from you… it’s been a long time since our days at Avondale :-). The sales pitches for these devices are very convincing, so don’t feel too bad. I certainly meant no disrespect to anyone who purchased one of these devices. When I started my investigation, I also wanted to believe there were savings like these ripe for the plucking, but if it were possible, legitimate companies would likely have been in this market a long time ago because achieving a 25% savings on an electric bill is a very big deal.
As for power that is returned, the motor in an electric power meter will, in fact, spin backwards if you produce power. Likewise, it will slow down if power is reflected back through it. Prior to getting our net meter for the solar array (which is digital and has no mechanical wheels inside), I switched on the array and can assure you that the old meter (installed in 1989) that had the familiar horizontal wheel would spin backwards as would the dials while the sun was shining. While waiting 3 weeks for the power company to come and swap out the mechanical meter for a digital net meter, the solar array managed to erase about a week’s worth of power usage. So there is no diode or other device that prevents current from flowing in both directions, even in the older meters.
If you want to do a power measurement, I would recommend the TED monitoring devices which will give you an instantaneous measurement of power consumption. If you put the PFC device on a switch, you’d be able to tell immediately whether you see any difference. It also shows your instantaneous power factor and KVA. You will be able to check whether your savings are real or just natural variation in monthly consumption or a result of consciously monitoring your power, which can also influence behavior.
Nico Viljoen June 7th, 2010 at 04:21
My name is Nico Viljoen and I live in Somerset West in South Africa. I am no engineer, but had good training in basic electricity and electronics – working for a company for many years.
What I can’t understand is all the comments on the Internet that say Passive Power Factor Correction does not work – is a scam and have no relation with electricity usage in a home environment.
Let’s forget about PFC and what PFC is and for now just look at a basic example.
I installed a “Mr.Power” PFC unit in my home in parralell with my main incoming supply after the main circuit breaker to make sure that the capacitance can filter through all the circuits more easily. Just after I installed the PFC unit, there was a drop in current (Ampere) of 1,9A.
I have then conducted random tests on the current drawn from our household appliances at the main incoming supply with the PFC unit disconnected and then again with the PFC unit connected.
My conclusion was that I have an average saving/difference of 1 Amp with all the random tests I have done during the day, evening and early mornings. (Average of 15 tests per day)
If the PFC unit cause an average drop of 1 Amp it means I draw less current, which means I will save at the end of the month on kWh
(I x V = W) 1 x 230 = 230 Watt (Ignoring any power factor)
The unit kWh is a unit of energy, which is power multiplied by time. Multiply the power saving of the equipment ( measured in W or kW) by time used (measured in hours) and I get the energy saving in kWh.
That means the following: .230 kW x 720hours (month) = 165.600 kWh
Our home electricity consumption per month = 696.258 kWh
696.258 kWh x R0.6444 (Rate) = R448.67 (Consumption only)
165.600 kWh saving x R0.6444 = R106.71 (Saving on consumption per month)
If I am correct with the above calculation, then it means that I save 23.78% on my overall electricity usage! (Keep in consideration that this is with the PFC unit only.
I can see that with the PFC unit there is a lttle bit of a grey area, because the test readings change constantly, but if I can save 23.78% on average per month I am happy and I don’t care how many people say it is a scam! I will realise a return on investment within six months!
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