Electricity bill

Discussion in 'Homework Help' started by Erica, Nov 5, 2011.

  1. Erica

    Thread Starter New Member

    May 18, 2011
    15
    1
    On the utility electricity bill the unit is kWh. Is the power measured a apparent power (kVA) or a true power (kW)?
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    It is supposed to be true power (Watts). If the power factor of your house gets too low (and you are pulling to many VARs), they can install a VAR meter and charge for those too. Most houses have PFs around .85 so it's not a problem.
     
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Mercifully, the electricity companies do not generally charge private customers for apparent power, nor penalise them for poor power factors.

    At least, that's the current state of play in my country (UK). Perhaps though in these modern days of smart meters and a quest for ever greater efficiency, one day this may come to us. How is it done in the USA?
     
  4. paulktreg

    Distinguished Member

    Jun 2, 2008
    612
    120
    True power.
     
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    That's intriguing: I had never heard of a domestic customer managing to annoy the supply people in that way. Would this be likely to happen with a truly domestic load, say with a lot of air conditioning, or more likely a small business using machines being run out of somebody's home?
     
  6. Evil Lurker

    Member

    Aug 25, 2011
    117
    23
    Personally I believe after my smartmeter was installed and the bill went up that the power company is now charging for apparent power.

    Those smartmeters are some tricky little bastards. One wrong setting in its firmware and you get billed out the wazoo.
     
  7. Erica

    Thread Starter New Member

    May 18, 2011
    15
    1
    Thanks for the reply. I also believe it is true power as the unit is kWh in the electricity bill. I am wondering how the traditional meter works and how the power is measured.

    The meter may be able to measure the r.m.s values of the voltage and current. But how can it get the power factor?
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I don't have all the answers, but one short one is they don't care. It the power company can squeeze more money out of people they will. It is like being presumed guilty before a court of law, it is up to you to prove their meters are not all they claim to be.
     
  9. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Small business, especially if it has a lot of motors running. It would be unusual, but the reason the power company cares is because it causes too much phase shift along the line. They have to put giant correction caps next to a house that looks too inductive. They care about the phase because it affects the generator's efficiency.
     
  10. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    I recall from 40 years back, there is a way to get the true power by putting the inductors of the meter motors at right angles (?) The old mechanical meters were supposedly true watt power. The new electronic ones are totally different.

    I guess my old brain was right:

    http://en.wikipedia.org/wiki/Electricity_meter
     
    Last edited: Nov 6, 2011
  11. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    There is no rule against asking your local power company how your meter works, and they probably know more than we do.
     
Loading...