Energy saving capacitor

What is it and does it really help cut your electricity bill?

If you've seen claims that an energy saving capacitor is going to slash your electricity bill by 10% to 25%, you may be in for a disappointment. The fact is, these devices, while they do reduce the measured electricity consumption for some older electrical motors, will do little or nothing to cut most household energy bills.

A capacitor is an electrical device that stores energy in an electrical field between two conductors, such as two plates of metal. People referring to or searching for 'energy saving capacitor' are usually referring to a device consisting of one or more capacitors, which attempts to average out the irregular pattern of energy use by inductive loads such as electric motors, to cut down on the amount of electricity you get billed for.

One area where a capacitor really does save energy is in devices such as wind-up flashlights and radios. These devices often use an energy saving capacitor to hold a charge you provide by winding a crank on the device, or by shaking the device to move a magnet up and down past copper coils, in order to charge the capacitor. The electricity can then be slowly drawn out of the capacitor to feed a low- power-consuming device such as an LED light (in the case of a flashlight) or a radio. Because the capacitor has very low power loss (compared to a battery) and the device being powered has very low power draw, you can find your way in the dark for quite some time with a few shakes of the flashlight (to charge up the capacitor), or listen to a goodly length of radio for a few turns of the crank.

But what we're typically referring to when we talk about an energy saving capacitor is a device touted to attach to your breaker panel and dramatically cut your electricity bills. That's what I'll focus on in this article.

You'll read sales pages for an energy saving capacitor that refer to improving the power factor of inductive loads. The idea is that voltage on an alternating current line fluctuates in a somewhat irregular form between positive and negative, changing polarity sixty times a second; an energy saving capacitor improves the power factor (the proportion of current in the wave form that the motor actually uses) so that more of the energy you draw from the grid actually gets used to do useful work, and less gets wasted because it wasn't needed at that precise instant. (It can be saved in the capacitor and released some tiny increment of time later.)

The explanation is usually quite believable and convincing, although the claims may sound too good to be true. And remember, if it sounds too good to be true, it usually is!

In my opinion, most of these devices marketed as power savers or sometimes as an energy saving capacitor are real, working devices that can actually save you electricity, but the claims that they might cut your power bill considerably are very hard to justify. You might realize some savings, but the savings are likely to be so small - perhaps in the realm of 1-5% - that any savings will be hidden by seasonal or random variation in your power use and in the accuracy of monthly meter readings.

Questionable claims: what's in a date?

I found one website that claimed that their energy saving capacitor would save you electricity on any induction motor made before January 23, 2006. First of all, why such a specific date? Did all manufacturers switch to some new motor design on exactly the same date, discarding all old motor stock when assembling their furnaces, fans, fridges, freezers, pumps, dehumidifiers, air conditioners and the like? When you see a very specific date like that without explanation, it ought to make you doubtful of the claims. How is anyone even supposed to figure out, before deciding to invest in an energy saving capacitor, exactly when the motors in all their electrical appliances were made?

How much of your electrical load is inductive?

There are two main types of electrical loads: resistive (anything that provides resistance to the electricity flowing through it, such as a stove burner, blow dryer heating coils, incandescent or halogen light bulb) and inductive (such as an electrical motor). Unfortunately, an energy saving capacitor only works on inductive loads.

One of the main reasons why an energy saving capacitor doesn't live up to its name is that inductive loads whose power factor can be improved by a capacitor typically don't make up that high a percentage of a typical household load. If you're running your fridge compressor, you might cut the energy use of the compressor by 20%, but you've still got those resistive loads such as lights, stove, electric heaters and so on, that don't involve an inductive load and so don't benefit from power factor correction.

Another reason is that an energy saving capacitor in and of itself is a very cheap, small device, made by the billions, and easily inserted into any appliance that has an induction load. As a result, manufacturers have been adding capacitors to anything with an electric motor for a number of years (certainly since before January 23, 2006 - from what I can gather, it's been at least 6 years as of 2009, as one device that claimed in 2008 to cut refrigerator losses by correcting power factor said your fridge needed to be at least 5 years old for the device to be of any use). Why did manufacturers start adding capacitors to electric powered motors? Well, with consumers always looking for more energy efficient appliances, and with capacitors being so cheap, it wasn't hard for the designers to see the value of adding a capacitor to their device and reducing its power consumption.

If you own an ENERGY STAR appliance containing an electric motor, there's a high likelihood that it already has a capacitor to deal with power factor. So there is no gain from buying a household energy saving capacitor, as far as that appliance goes. No gain from already-efficient inductive loads, no gain from resistive loads - so where's the benefit of an energy saving capacitor?

Claims of percentage gain

Another thing you will notice if you read the sales pages of people selling power savers or similar devices, is that they hint at potential savings but they don't actually guarantee any particular level of savings. Of course, they can't, because they can't predict the percentage of your household electrical load that is inductive (and not already corrected by an energy saving capacitor inside the device itself). We shouldn't fault such companies for being vague on this given that they really can't be specific - of course your results may vary. But the sales copy often makes things seem more cut and dry than they really are. You'll see claims of a range: a drop of 10 to 25% in your electrical bills. But read more closely: are they guaranteeing that? Or just saying you 'should see' or 'might see' that kind of reduction? They give you a hypothetical level of savings that can only be realized if you either have mostly inductive loads in your house, or all the electrical motors in your appliances are older vintage models, and hope you don't notice (or can't be bothered to ask for a refund) when your savings don't add up to the claims.

And even assuming you did see a gain of 10 or 25%, how would you know whether the gain came from that or from something else?

Look for the testimonials provided for an energy saving capacitor. Do customers claim to have cut power use consistently month after month while using these devices? Or is there just a claim that power use dropped by X% after the first month? Here's an interesting scenario: say one hundred people buy such a device and install it in their home. Since everyone's power use fluctuates month by month, even if the energy saving capacitor does no good at all, some people are bound to see a drop in power use from one month to the next, while others will see an increase. Those who see an increase in power consumption may ask for a refund for their energy saving capacitor. Those who see a small gain will be moderately happy, or at least won't complain, while the small number who, for reasons unrelated to their energy saving capacitor, see major gains, will write a glowing testimonial. The testimonial gets published, and the person who asked for the refund gets their money back but doesn't get anything published about how badly the system 'appeared' to work for them.

Another point in favor of this scenario (namely, where the small percentage who miraculously cut energy costs while using such a device, are the ones whose testimonials get published) is the fact that often people create the result they want to see. For example, it is well established that one of the best ways to get people to cut their electricity usage is to get them to measure their electricity usage. As I explain in How to save electricity, that's exactly what helped my family cut our electricity usage by 50% or more. If you install an energy saving capacitor expecting it will save you energy, chances are, you'll start measuring your electricity use on a more regular basis. And chances are reasonably good that the mere act of measuring electricity use will cause you or your cohabitants to be more careful about turning off lights and avoiding other big energy using activities. So you could wind up cutting your electric bill once you install one of these devices, not because it saved you anything, but because you changed your energy use habits.

But if there's a guarantee, it must be for real, right?

Some power saving devices even come with a money back guarantee. That's great, but again, think of the hundred-customer scenario. If the money back guarantee is good only for three months, there's still a chance that some customers will see an improvement because of random variability, while others will see no change or an increase in power use. Those who see no benefit or an insignificant one may decide it's not worth fussing with a refund request, and keep the device, assuming that savings will materialize later. Those who see even a small an improvement will keep using the energy saving capacitor, with one or two of them even writing a glowing testimonial, even though it may be pure chance that their power usage dropped. Finally, some of those who see an increase in usage will probably ask for a refund. But my understanding is that these devices are simple enough to manufacture that the $300 to $700 price tag still gives the seller a healthy profit even if 80% of those who buy the device return it for a refund (and of course the seller can still turn around and sell the used device to the next prospect).

Another thing to watch is the content of the testimonials. First of all, how do you know the testimonial wasn't fabricated? Second, what environment does the testimonial relate to? For example, I found one site had a testimonial from a company that ran several large water pumps. Unless you run several large water pumps in your own house, you're unlikely to see much gain with a residential energy saving capacitor.

Factory benefits

Of course, there's a reason a company using many large water pumps sees a drop in their power usage when using an energy saving capacitor system. For large electrical motors there really is a savings. Industrial settings use larger versions of these devices all the time because there is a real benefit for them. That's one of the arguments some sites selling these devices will use: if giant factories use them, and save millions on their utility bills, why aren't you using them too?

Well, because your house isn't a factory. You don't have 300-horsepower pumps or printing presses or stamping machines. You've got a half-horsepower compressor on your fridge. So there just isn't much benefit for household-level use, especially if your induction loads already have built-in capacitors.

Conspiracy theory

The last argument I'd like to touch on - one you'll see on many of the websites that are trying to sell you an energy saving capacitor - is that the utilities don't want you to know about these devices. The argument is that utilities exist to make money, and therefore the more power they can make you consume, the more money they'll make; and your using a power saving device like this to cut your energy use will somehow deprive the utility of profits.

This is an interesting argument, and there may be a few places on earth where utilities are trying to get people to use more energy, but in the vast majority of places, electrical utilities are regulated and are either strongly motivated, or legally required, to do everything possible to reduce demand among their customers. In some cases utilities aggressively promote conservation, because from the utility's perspective it's cheaper to convince someone to cut their electrical use than to build extra generating capacity. Why do you think utilities and governments have all these programs to give away compact fluorescent light bulbs or to give people rebates on the purchase of an ENERGY STAR appliance in exchange for trading in an old, inefficient one? Certainly not because they're trying to get you to burn more electricity. They want you to cut back! If these things really did work, utilities would be banging at your door begging you to install one!

The best way to save electricity is not to use it

If you still think an energy saving capacitor is going to cut your electricity bill, go ahead and buy one - from someone who offers an iron-clad guarantee. Because as far as I can tell, the chance is pretty good you'll be wanting a refund within a few months. A few people - particularly those with several 300 horsepower pumps in their basements, pumps that, of course, were built before January 23 2006 - will see a drop in their utility bill. Most will see no change at all, or one so small that the $300 to $700 they paid for the energy saving capacitor will have a payback period measured in decades.

But the best way to cut your electricity bills is to stop using so much electricity. As I explain in How to save electricity, for most North Americans there are lots of ways to cut electricity use, and by measuring, deciding where the big energy users in your house are, cutting use accordingly, and measuring again, you can cut your use dramatically. Maybe not by 50% as we did, but certainly by at least the 10% to 25% the sellers of these devices claim.

And the best thing about cutting your power use yourself is, you don't have to buy these overpriced devices. For a mere $20 or so you can buy a device like a Kill A Watt meter, start measuring the electrical consumption of household devices and appliances, and see real savings start to pile up in no time.

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