Electricity Saving Tips For Homes And Offices

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

By on April 22, 2016

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

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