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Is This True?

Is This True?

Is This True?

I Have Heard that by placing a capacitor in parallell with your home electric main you can lower your power bill.

Two theories have been forwarded as to the reason

1)<My Favorite> The Cap. brings your home "system" closer to a Unity power factor which would lower the current
Kw=KVA If KVAR is removed (this assumes the meter measures KVA-Hours) Since many large house hold loads are inductive fridge, A/C, etc.. this makes sense.

2) Meter reads KVAR Therefore too much capacitor makes the meter turn backwards! this sounds a litle absurd.

I Realize this is probably Illegal, The person telling the tale's "cousin's-uncle's-friend's-brother" went to prison, etc,etc,etc.....

What I guess I'm asking is how does the electric meter work,
does it measure KW, KVA, or KVAR? And if this isn't Illegal why isnt everyone doing this? (If the story is true)

Just checking on what sounds like an "Urban Legend"

RE: Is This True?

By adding a capacitor to your service, you will reduce inductive kVARs that the supplier has to provide and that are not counted by your kWhr meter. This meter will not be affected by capacitive or inductive kVARs. Generally, suppliers are concerned with excessive kVARs supplied to consumers since they have to produce them and they are  not paid for them. Therefore, the supplier may enforce power factor limit (which implies kVAR limit) per consumer. Once the limit is exceeded, the consumer has to pay for the excess or compensate the power factor down below the limit by adding power factor compensating capacitors if the excessive kVARs are inductive and adding power factor compensating inductors if the excessive kVARs are capacitive (which is rare).

RE: Is This True?

Definitely an urban legend.  The meter reads kW and will not register a change in kVAR, assuming that it is properly calibrated.  While some utility rates charge industrial customers for kVAR (or kVA), which makes power factor improvement by the addition of capacitors worthwhile, I don't think that there are any cases where this would apply to your home service.
Where loads are predominantly reactive, capacitor addition can reduce supply voltage drop by reducing feeder load.  This is not likely to be a concern for home service, except maybe in some rural areas.

RE: Is This True?

Jbartos and peterb are correct in that KWh meters mesure KWh, only. In fact, utility companies test their meters a .5 PF to make sure that they are unaffected by KVARs. I disagree with peterb on one point, though. Adding capacitors to an inductive load will actually raise the voltage at the service. This is because the utility system will not have to provide the reactive current which then lowers the voltage drop in the network. The resulting increase in voltage at the service then increases the current through resistive loads (I=V/R), thus increasing the power (P=V*I). Thus, it would seem that adding a capacitor at the electric meter at your home may actually increase your energy consumption, not decrease it as was claimed.

RE: Is This True?

CurtJ, I agree with what you say - but what I wrote was that the voltage DROP would decrease, which means that the voltage would increase. While the consumption of resistive loads would increase (P=V^2/R), the consumer would be getting more actual output for their dollar.

RE: Is This True?

Sorry, peterb. My eyes skipped over the word "drop" in your response. I see we do agree on the voltage issue.

RE: Is This True?

One little item may have been overlooked, namely, if  you add power factor compensating capacitors to your service, which has a very large voltage drop (more than 10%), then you lower the voltage drop and increase your outlet voltage to your loads that may suffer by undervoltage conditions (low life-cycle), e.g. motors, lamps, ballasts, some electronics, solenoids, coils, transformers, doorbell, etc. Then, it may actually pay to install those capacitors in exchange for paying a little bit more for electricity.

RE: Is This True?

Thanks again to all, guess it was just some "urban legend".
Probably with some basis in industry, but definitely not for home use!

RE: Is This True?

dan, one thing you mentioned that everyone else seems to have missed is that making a connection to the supply side of a domestic single phase meter( i take it this discussion is about single phase? ) is COMPLETELY illegal. I hate sound like a sour puss but why go to the trouble of calculating inductive reactance et cetra when you might as well just stuff both the live ends in a block and take the meter out of cct ?  
either way it is illegal and there is definitely no way would i ever try anything like that  

good luck and every success


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