• EEVblog #848 – Home Energy Savers BUSTED!

    Dave debunks the home energy saver you can buy on ebay for a few dollars.
    Can a capacitor in a box really save you money by fixing the power factor of appliances? Or will it just end up costing you more?
    Dave does some measurements to bust the scam wide open.
    Forum HERE

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      • tlhIngan

        Big industrial customers aren’t charged on apparent power either. They’re billed on real watts and a surcharge if their power factor exceeds certain bounds. Apparent power isn’t “consumed” – it’s power that flows back and forth between the utility and you. So for half of the sinewave, you’re “drawing” apparent power, and for the other half, you’re “returning” it back to the utility. Only real power is actually “consumed”.

        Big industrial customers however are often told they need to maintain a certain power factor – apparent power still creates real losses and the equipment must handle the apparent power consumption as well, so if your power factor exceeds the margin they will bill you for the extra costs incurred.

        All the customers do in that case is figure out what their power factor is and then apply either an inductor or capacitor bank to correct it. (Remember, apparent power is caused by an inductive or capacitive component and you correct for it by the opposite).

        It’s also generally a concern on three-phase equipment since you don’t want the power factor on one phase going out of whack – unbalanced consumption on phases causes all sorts of issues.

      • honey,how are you

      • blipton

        So the amount of energy consumed is KWh or Wh… the utility bill would never say KW or W, right? The latter is the instantaneous energy usage (J/s), where the former would be just Joules?

        • Leon bed

          Basically yes.

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