I’m sure a lot of you have seen this on HSN or in the malls — that wattage-zapping device which claims could lower your electricity bill by as much as 30%. I got curious so we tried it out several months ago.
The theory behind the device is that it normalizes the current running thru the house (hundreds of meters of copper wiring running thru the walls) and thus reducing the power consumed thereby lowering the electric bill. I’m no electrical engineer so I can really explain it very well so an actual test should be in order.
The device, named Power Saver Max, is plugged into a wall socket and does all the trick. And it costs a whooping Php3,500 a pop. It used to be Php7,000 several years ago when it first became public.
Of course, there are various other factors that might affect the fluctuations in power consumption around the house but by taking monthly samples, we may be able to see some sort of a trend.
For the last 9 months, our Meralco bill has been pretty consistent with power usage in the vicinity of 750 kilo-watt hours. Then in October, we tried that wattage-zapping device. The sales guy guaranteed that if we don’t get lower bill in 3 to 6 months, we can return it and get my money back.
The October usage went down but the following month, it went back up again only to go down in December. Those drops accounted for just 11% and 16% reduction on the bills. I’m not yet convinced so I’m giving it another 2 months.
Anybody else had this one at home? Did you notice any changes in your electricity bills?
Our electric bill looks much like the trend you posted and we’re not even using Power Saver Max (PSM). The truth is, your monthly power consumption depend on a lot of factors and it may fluctuate either way. If it goes up, you get your money back. If it goes down, they get the sale, whether it was due to PSM or not.
Based on the description of the product, I’m assuming that its main function is to bring the power factor (p.f.) closer to unity. This is accomplished by putting capacitors in parallel to your electrical load. The effect is a phase shift and a reduction in current (due to vector addition of resistive, inductive currents with the capacitive current). This is what the salesman shows you in the store. Instinctively, we translate lower current to a reduction in power consumption. That is why they never use purely resistive loads in their demo, because it doesn’t result in a reduced current reading. However, average AC power is a function of Voltage, Current and Power Factor. With voltage being constant, a lower current, and a higher power factor, the net effect on average power is negligible.
It is easier to understand it with the power triangle: Apparent power (VA or kVA) is the hypotenuse, reactive power (kVar) is the opposite side (vertical) and real power (kW, the value we pay for) is the adjecent side (horizontal). The cosine of the angle is the power factor. What the Power Saver Max does is add a negative reactive power (capacitance load) so the effect is the reactive power (kVar) will be pulled closer to zero, reducing the angle (therefore increasing the p.f. making it closer to 1). The real power (kW) doesn’t change at all. Apparent power (kVA) is reduced (hypotenuse becomes shorter). With voltage being constant at 220 RMS, this means that the current has been reduced, hence the result of the demo meter reading that the salesman at Handyman or Ace Hardware are trying to show us. Unfortunately, we are billed for Real power, not Apparent power.
The only advantage I can think of with using this product is that it reduces conductor load and would lower line losses (I^2*R losses), but that’s very insignificant. However, for industrial consumers, Meralco imposes penalties for having low power factor, so the industrial consumers invest in having capacitors installed (or synchronous motors a long time ago, which has the same effect) to improve their power factor. Meralco does this because this would have a big effect on their line losses of their transmission lines (rememeber, higher current, higher line loss).