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.
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Nico: The current is meaningless without knowing the phase relationship between the current and the voltage, which is what PFC devices change.
You can have two houses, both fed at 120V and both with 10A of current flowing between the house and the utility. But one of them can be providing 10A from a solar system and one of them can be drawing 10A for a heater. The meters will read very differently.
A theoretically perfect PFC correction device will reduce the current by ensuring you don’t return any power to the power company.