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Electricity Saving Tips For Homes And Offices

Power Saver Devices or Capacitor Banks – do they really save electricity?

By on January 22, 2014

Capacitor Bank

Several times we come across devices that are sold and branded as power savers and claim to reduce significant amount in electricity bills. The questions that come in our minds at this stage is: Does it really save electricity? Is it legal? Can it work for my home or office or factory? The answers to these questions are very simple: Does it save electricity? Yes but only in certain cases. Is it legal? Absolutely. Can it work for my home or office or factory? Again only in certain cases.

So what is a Power Saver Device?

As we discussed in our previous post on Power Factor, there are 2 kinds of electricity loads: resistive (e.g. lights, water heaters, coil heaters, etc) and inductive loads (e.g. ceiling fans, pumps, air conditioners and refrigerators). For resistive load, the energy (or electricity) supplied by utility is mostly same as the electricity used by the appliance. But in case of inductive loads some energy is used up to create magnetic field that is not useful. And the formula for the same is:

kVAh (energy supplied by utility) x  P.F (Power Factor) = kWh (energy used by appliance)

A power saver device improves the power factor that results in lesser kVAh (energy supplied by utility) per kWh (energy used by appliance). It does so by reducing the electrical current drawn from the utility.

What are Capacitor Banks?

Power saver devices are nothing but capacitor banks. Capacitor banks provide capacitive load which is opposite of inductive load. When put in parallel with inductive load (like ceiling fans, pumps, ACs, etc) they improve the power factor thus taking less energy (from utility) for the same appliance (or same amount of work). Capacitive load in parallel with inductive load makes the system resistive.

Where do these devices help?

These devices are good in following situations:

  1. When there is lot of inductive load in the system (lots of pumping, air conditioning, refrigeration and fans) and the utility bills in kVAh.
  2. When the wiring is not good and lots of electricity is being lost as heat through the wiring. Lesser current because of power savers can help reduce heat loss through wiring.

Can it help at your home?

Typical residential (even for housing societies) billing happens in kWh (energy used by appliances) and thus there is no apparent benefit of power factor correction. Unless wiring in your house is too bad, you will not observe much saving by using a power saver device. Power saver may reduce the heat losses in wiring, but that will not be significant enough to justify the investment.

Can it help in your office or factory?

In some commercial and most industrial sectors billing happens in 2 ways:

  1. The contracted load is in kVA (or demand based billing).
  2. The billing happens in kVAh units.
  3. There are power factor penalties/rebates.

If billing is in kVAh, then by using power saver devices the kVAh consumption is less and the number of units that show up on electricity bill will be less.

If billing is in kVA (or demand based billing), you will reduce your maximum demand by putting power saver devices and thus save on fixed costs.

If there are power factor penalties then you save by improving the power factor of your premise and in fact can gain with better power factor rebates.

In case none of the above 3 conditions apply in your case, and then you will not save much by using a power saver device.

References:

http://www.energymanagertraining.com/announcements/EE08_result/SanjivArora(A).pdf

http://en.wikipedia.org/wiki/Power_factor

http://www.engr.colostate.edu/ece-sr-design/AY06_07/power_factor/PFC.pdf

Have question, doubt or comment? Leave a message (please submit once as the comments take time to appear online)

There Are 10 Comments

  1. robin says:

    can i have a schem diagram for this application sir/mam because im still a student of (M.U.S.T.)and requirable for my project .please me for need help.,.thnx .just pm me 4 my email add fb.

    • Abhishek Jain says:

      Hi Robin,

      Sorry, we do not have a scheme diagram for this. You may search more on internet and may find it somewhere.

      Regards,
      Abhishek

  2. Electrician Rochester says:

    What a nice and really informative post to read… Thanks for sharing

  3. harish anir says:

    i have installed a secure make energy meter on a capacitor bank having 240 kvr capacitors. v 425 amps 260 and kw =9.35 and after 21 hrs kwh shows 201. that means approx 220 units consuming a APFC panel. is it possible ?

  4. Gary says:

    I get frequent power interruptions for less than a second at my house, I was told that a capacitor bank would prevent that from happening. I am worried that the frequent outages will damage my TV frig., is that correct?.

    • Abhishek Jain says:

      Hi Gary,

      Frequent outages can certainly damage the appliances and the first thing that we suggest you is to contact your utility about it. What you say sounds more like voltage fluctuations, and a voltage stabilizer instead of a capacitor bank should be able to help you. But do check with your utility for the same. Hope this helps.

      • Abhishek Jain says:

        Do check this link ( http://northpower.com/network/services/voltage_fluctuations ). It may be of help.

  5. Roshan says:

    Capacitor has to be connected in 3 Phase.Sometimes there exist a real possibility that the wire connection has tripped to 2 Phase.In such an unforeseen event the Capacitor will itself become an Drain on current.You will observe your meter reading showing rapid Unit consumption.In fact the Electricity used by 2 Phase Capacitor will be around 10 times your average monthly Consumption.So kindly check on the wiring on a regular basis.Also remember that you need to have Wire/Cable capable of taking inordinately high discharge amperage.Wire/Cable should be thicker(over designed ).
    When your Motors are not in use please shut the Capacitor.
    The Capacitor should be started only when you have an rotating Motor being operated.
    If you are advised to buy 25KVAR capacitor,please buy 5 Capacitor of 5KVAR rather than 1 Capacitor of 25 KVAR.
    A good example of capacitor’s high current discharge ability is Camera Flash.

  6. Roshan says:

    When power factor is .8 ,it means you have used only 80% of the electricity supplied by your utility.The remaining 20% is wasted.There are various reasons why your Machines(Inductive load) is unable to fully utilise the 100% Electricity supplied to you.
    The utility provider knows the problems at your end ,bills you for the 100%,and also imposes extra PF penalty charges.
    Simply put you lose on 20% electricity charges as also additional PF Penalty.
    So get yourself a good quality Capacitor,if you run a factory.
    Please note you need not use a Capacitor for your HOME,absolutely never.
    All home appliances have capacitor tailor made for its application.

    • Abhishek Jain says:

      Well said Mr Roshan. In fact utilities also provide rebates on better power factor. So there can be a lot of savings if factories and commercial connections try to improve their power factor.

      Regards,
      Abhishek

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