Power Savers. Do They Really Save Electricity Bills?

29 October 2008

Electricity rate has gone sky high. Many will try to save electricity bills by trying out the installation of energy saving devices. Now, there are Power Savers available in the market. Do they really save electricity bills?

What are these Power Saver?
There are many different types of power savers in the market. Some are floor mounted, others are just small appliances with a 3 pin plug. All claimed to have saved electricity energy; some claimed to save up to 35%. This article will examine if they will really save your electricity bill.

The Salesman's Pitch
In the sale booth, the salesman can demonstrate to you that the Energy Saver can save energy.

Doesn't that Saves Energy?
What the salesman demonstrated is that by installing the Power Saver, the electric current is reduced. But that does not necessary mean that your monthly electricity bills will be reduced.

First, let us find out what are really inside these Power Savers. If one were to strip open the casing, one will find small electric capacitors.

What are these Electric Capacitors?
These are electronic components we often find in electronic appliances such as in Televisions. They may cost around $ 2 or $ 3 each. They are often used to smoothen electrical circuits to get rid of spikes. They can store up electricity energy just like our car batteries. In the application of Power Saver, the capacitors serve to correct the power factor of an electric appliance but they correct only the reactive and not the active power usage of an appliance.

What is Power Factor?
Power factor is a jargon used in electric and electronic power industries. It is nothing but a term defining the relationship between the active and reactive power of an alternative current or electric waves. Power factor is often referred to as the mathematical "cosine" of the angle between the active and the reactive power. It is one of measurements for the quality of the power supply system.

What are Active and Reactive Powers?
Our electricity supplies active as well as reactive power to our homes. In simple layman term, the active power (measured in KW) is for us to produce work or heat whereas reactive power (measured in KVR) is related more to energy storage part of a system. For example, an appliance having pure resistances, such as electric heaters or irons, uses only the active power whereas an electric motor will use both the active power as well as the reactive power.

KWh Meters
By name, KWh meters measures only the active power (KW) of the electricity usage. The meters are constructed such that it ignores the reactive power usage. As Power Saver corrects only the reactive power, it does not save electricity bill directly.

Isn't the Reduction in Electric Current reduces KWh Meter Reading?
The ordinary home KWh meters are of electromechanical type. Each meter has 2 coils, a current and a voltage coil. They are arranged with 90 degree phase shift to always measure the active power usage of the electricity. Depending on the meter construction, many are affected only by the active power used by the network but the power factor of the network does have some effects on the meter reading.
In the case where the current drawn does affect the KWH meter reading, it shall be noted that most home appliances are either of resistive load or already installed with power factor correction capacitors in order to comply to the manufacturing specification. Therefore, additional capacitors provided by Power Saver will not serve much purpose. On the other hand, an over correction with more than enough capacitors may increase the current drawn.

It is therefore advisable not to install the Power Saver unless one is sure that the electric appliances to be used do not have the required capacitors already installed. Even then, the electricity bill saving may be minimal except for some heavy appliances such as air conditioners, where some users of Power Saver claimed to have saved some electricity cost.


Anonymous said...

You are right! Correcting the power factor reduces the apparent currents. However, the real power, does not get reduce at all!

Anonymous said...

I have heard that Power Savers effectively/actually cause your meter to run more slowly or even backwards! We have an electronic meter. Can you tell me if this is true, please?

Sky Juice said...

Most power savers are made of capacitors. These capacitors can only do a phase shift in the supply to reduce the current or KVR/KVA power component. If your electronic meter is reading KVAh instead of KWh, these power savers may save some of your electricity bills (check with your supply authority).
It is very unlikely that the meter will run backwards. To make the meter running backwards, one would have to supply electricity back to Grid. This can be done only if you have a micro-turbine or any generator that can generate electricity and sell the excess back to the Grid

Anonymous said...

You may not believe this. But there was an old electrical meter that actually turns backward when the water pump of the house is turned on. It ran backward faster when we turn an electrical appliance was on. This was an amazement to all of us and never knew how it happened. This is 100% true.

Sky Juice said...

It will be hard to imagine without knowing your setup.. unless one use diesel to run the electrical pump or there is a faulty meter. Enjoy while you can.

adson stone said...

Hi friend how are you I want share with you some tips about how we can save energy because now days energy short fall to much so we can save energy for our future. Ceiling insulation is the most effective barrier against the summer heat and the winter cold. A minimum of R3.5 is recommended for most areas in Victoria. Keep the heat inside during winter and the hot air out in summer by sealing up any gaps and cracks in external walls, floors and ceiling. Seal external doors using draught stoppers or 'door snakes' at the bottom and weather stripping around the frames. Close blinds, curtains, windows and doors on cold days to keep the heat in, and in summer use outside shading to keep the sun off the glass. Dress for the weather – in winter, wear extra layers inside and lower your heating thermostat. By setting your heating thermostat between 18-20°C, you can decrease your running costs by up to 10%. In summer, wear lighter clothing and keep your air conditioner’s thermostat between 24°C – 26°C Your fridge runs 24 hours a day 365 days a year. This adds up and makes it the most expensive appliance to run. Make sure that the door seal is tight and free from gaps so cold air doesn't escape. If you have a second fridge, give it a winter break - just turn it on when you need it. Only heat or cool and light rooms you are using. Where possible, zone your lighting and ducted heating or cooling and close off doors to unoccupied rooms.
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