Electricity Saving Tips For Homes And Offices

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

By on May 3, 2015

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.

Capacitor Bank

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



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23 Comments on "Power Saver Devices or Capacitor Banks – do they really save electricity?"

If you have any question or comment, please leave a message here. We try to reply to questions in the sequence they come in. We work from Monday-Friday 10AM-7PM. If we know the answer we try to reply to the question within 3 days.

Guest
Avik
July 1, 2015

It’s true that we can use a capacitor bank to supply the reactive power to a reactive load and stop the voltage from dipping . so can we use a capacitor bank along with a Ac to maintain the overall house vol.

Guest
Gordon
March 31, 2015

Thank you for your all Articles on Power Factors and Capacitor Banks. I found them very very informative. Have you tested any specific Power/Capacitor Banks that would work great with saving electricity used by AC Units and large Fridges? Please recommend to me at least 2 good ones you have found. Very much appreciated.

Guest
Gordon
April 2, 2015

Thank you. If you were to try a few, which ones would you try? I am trying to select a few, so I can do a comparison. Thanks.

Guest
Gordon
April 8, 2015

Thank you for your help. Will try them.

Guest
PRAKASH
December 29, 2014

Dear Abhishek
I live in flat(First Floor) in a thee story house.
One electric meter(main) insttled in ground Floor and Two sub-meter insttled First Floor and Second Floor.
House onwer received electric bill from me on basis of sub-meter shown reading. and also second floor.
But problem is mentioned below:
Electric bill (main meter) come from electricity department is low compare to my bill+ second floor bill (sub-meter).
Whereas main meter show three story used electricity.
We also replace sub-meter but problem is same.
So, my question is any solution for this problem ?
Or Power Saver Device is solution ?
Pl. help me.

PRAKASH

Guest
PRAKASH
January 1, 2015

owner have installed submeters.
Answer of your Question:

(1) Owner
(2) Rs. 5/- per unit
(3) Chandigarh

Guest
PRAKASH
January 2, 2015

My problem is meter reading not amount like total reading is 396 unit (main meter) in a month wheras my reading is 200 unit (only first floor) and second floor is 175 unit. Rest unit (21) consumed by Ground floor, but practically not possible bacause home appliance almost same all three floor. We also replace sub-meter but problem is same.

My question is Power Saver Device is solution ?

Guest
robin
February 11, 2014

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.

Guest
Electrician Rochester
December 30, 2013

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

Guest
harish anir
November 7, 2013

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 ?

Guest
Gary
June 5, 2013

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?.

Guest
Abhishek Jain
June 6, 2013

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.

Guest
Abhishek Jain
June 6, 2013

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

Guest
Roshan
November 19, 2012

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.

Guest
Roshan
November 18, 2012

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.

Guest
Abhishek Jain
November 18, 2012

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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