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kWH & utility cost Q
|
|
|
| Hello all,
First time poster on this particular group; from the look of some
of the posts this might be the right place to ask my question.
Before anyone comments, yes, I have too much time on my hands
;-]. I'm in forced retirements, health issues, and am trying to
save a couple of bucks.
I'm in the US, far northern NY state to be exact.
I can measure:
Volts rms, Current rms, Watts, Frequency, Power Factor, VA and
time.
I can calc my cost per kWH from my utility bills.
Where I get lost is the PF (Power Factor). I was surprised to
find PF down in the ranges of 50 to 80% on many appliances; I
expected much higher. Anyway:
I know 1,000 W for one hour is 1 kWH.
But ... for cost calculations, how does the PF affect that?
Clarifications would be most appreciated!
Here's the kind of things running around in my head that perhaps
someone could also clarify for me:
If I consume 1 kWH over one hour, with a resistive load, then I
have to pay for 1 kWH of power. Right?
Then in two hours I'd have to pay twice that amount for power;
it follows logically.
But, what if I get the 1 kWH measurement at the one hour point,
but ... the meter indicates the PF is 50%.
Am I going to pay for half, one, or 1.5 kWH's?
While I understand intellectually what PF is, I'm confused trying
to figure out how I'm charged for it on a residential service (no
load caps, etc. as industrial power requires). I think it's not
knowing what the electric meter measures (or displays) vs. the
meter readings from my meters that are confusing me. Google et
al, even my own power grid folk are no help in getting a handle
on this that I can understand fully.
Over the period of a day/week/month/year, the error, depending
on what I do or don't do with PF could become rather large, as in
plus/minus 50% for my example.
Thanks in advance for any assistance,
Pop
--
---
twaynesdomain.com:
Best little website in
the North Country!
| |
|
|
"Pop" <nobody@devnull.spamcop.net> wrote in message
news:FZWdnYjExod0PebeRVn-rw@usadatanet.net...
> Hello all,
>
> First time poster on this particular group; from the look of some
> of the posts this might be the right place to ask my question.
>
> Before anyone comments, yes, I have too much time on my hands
> ;-]. I'm in forced retirements, health issues, and am trying to
> save a couple of bucks.
> I'm in the US, far northern NY state to be exact.
>
> I can measure:
> Volts rms, Current rms, Watts, Frequency, Power Factor, VA and
> time.
> I can calc my cost per kWH from my utility bills.
>
> Where I get lost is the PF (Power Factor). I was surprised to
> find PF down in the ranges of 50 to 80% on many appliances; I
> expected much higher. Anyway:
> I know 1,000 W for one hour is 1 kWH.
> But ... for cost calculations, how does the PF affect that?
>
> Clarifications would be most appreciated!
>
> Here's the kind of things running around in my head that perhaps
> someone could also clarify for me:
>
> If I consume 1 kWH over one hour, with a resistive load, then I
> have to pay for 1 kWH of power. Right?
> Then in two hours I'd have to pay twice that amount for power;
> it follows logically.
>
> But, what if I get the 1 kWH measurement at the one hour point,
> but ... the meter indicates the PF is 50%.
> Am I going to pay for half, one, or 1.5 kWH's?
>
> While I understand intellectually what PF is, I'm confused trying
> to figure out how I'm charged for it on a residential service (no
> load caps, etc. as industrial power requires). I think it's not
> knowing what the electric meter measures (or displays) vs. the
> meter readings from my meters that are confusing me. Google et
> al, even my own power grid folk are no help in getting a handle
> on this that I can understand fully.
> Over the period of a day/week/month/year, the error, depending
> on what I do or don't do with PF could become rather large, as in
> plus/minus 50% for my example.
>
> Thanks in advance for any assistance,
>
> Pop
A residential meter rate that charges for PF? That news to me. Where I live
the utilities do not concern themselves with PF for residential customers.
Please provide the make and model of the meter they have installed on your
home. I would like to look it up.
What are the specifics of the rate your on? Some of my commercial customers
get charged for PF. They base it on the 15 minute demand window that they
use.
What are you using to measure PF with?
| |
|
| Hi,
Comments, responses inline:
"SQLit" <sqlit@qwest.net> wrote in message
news:ymOef.59$I14.872@news.uswest.net...
:
: "Pop" <nobody@devnull.spamcop.net> wrote in message
: news:FZWdnYjExod0PebeRVn-rw@usadatanet.net...
: > Hello all,
....
: > I can measure:
: > Volts rms, Current rms, Watts, Frequency, Power Factor, VA
and
: > time.
: > I can calc my cost per kWH from my utility bills.
: >
: > Where I get lost is the PF (Power Factor). I was surprised
to
: > find PF down in the ranges of 50 to 80% on many appliances; I
: > expected much higher. Anyway:
: > I know 1,000 W for one hour is 1 kWH.
: > But ... for cost calculations, how does the PF affect that?
: >
: > Clarifications would be most appreciated!
: >
: > Here's the kind of things running around in my head that
perhaps
: > someone could also clarify for me:
: >
: > If I consume 1 kWH over one hour, with a resistive load, then
I
: > have to pay for 1 kWH of power. Right?
: > Then in two hours I'd have to pay twice that amount for
power;
: > it follows logically.
: >
: > But, what if I get the 1 kWH measurement at the one hour
point,
: > but ... the meter indicates the PF is 50%.
: > Am I going to pay for half, one, or 1.5 kWH's?
: >
:..
: > Pop
:
:
: A residential meter rate that charges for PF? That news to me.
Where I live
: the utilities do not concern themselves with PF for residential
customers.
: Please provide the make and model of the meter they have
installed on your
: home. I would like to look it up.
Sorry; guess one could have read it that way. No, the meter does
NOT charge for PF that I know of. The PF numbers, also, came
from my meter. Niagara Mohawk of National Grid is my supplier
and near's I can tell they don't mess with residential PF's. I'm
just surprised as some of the measured PFs I am seeing is all.
Our power meter's recently been changed to one of the newer modem
types that "calls in" the usage over the power lines. Nothing
unusual, I don't -think-.
:
: What are the specifics of the rate your on? Some of my
commercial customers
: get charged for PF. They base it on the 15 minute demand window
that they
: use.
Standard Residential rate. Varies from ten to 11 cents per kWH,
depending on whatever - no idea unless it's usage amounts. I'm
using "real" cost, BTW; total bill divided by kWHs delivered.
:
: What are you using to measure PF with?
I have a cheapie meter that reads Vrms, Arms, Watts, VA, freq, PF
and kWH. It's just a cheapie P3 "Kill-a-watt" meter. PF's
calculated by simply dividing VA by Watts inside the meter; I
think that's the right way to do it anyway, isn't it? Just got
it and just yesterday dug out all my old meters to check its
accuracy, at least ballpark wise.
I compared its readings to a couple old VTVM's I have hanging
around, and a borrowed current probe and it's reasonably
accurate, surprisingly enough, so I'm XXX-u-me-ing it's giving me
ballpark, at least relative, usable results. It looks pretty
reliably in the plus/minus 5%; I'm guessing it's about 2.5% high,
best I can figure. Most of my equipment's out of cal now but
they seldom ever needed much cal work when I was using them
daily. My scope's shot so I can't do any real peak work on the
wave form.
So, what do I do? Still looking for answers to my previous
questions. (';=]
Pop
:
:
:
| |
| Rowbotth 2005-11-16, 11:21 pm |
| In your case, PF is not power factor. It think it might be a multiplier
to do with the PT and CT ratio built into the meter. (It has been a
while, but from my memories of what they tried to teach me about
metering, I think this is true...)
PF either means that what you read is 0.5 of what you used, or what is
used is 0.5 of what is read. I forget which.
The easiest way is to look at your bills. They may (mine do) give you
the date when the meter was read. This probably happens the same day
every month - more likely if the meter calls in the number, and a
machine does the calcs.
Anyway, you want to figure out when this date is and then next month go
write down the number on the meter, at both the start and end date of
the "metered Month". If the difference between the two numbers is what
your power company charges you for consumption, then you know what the
PF means to you. Not much.
But if you have to adjust the number you calculate to get what you are
billed on, then you now have clarification and understanding. (Well,
about this, any way!)
Have fun. (Oh, you got the theory of calculating PF from VA and Watts
down pat. Well done!)
H.
In article <r-SdnTvke9MMQObeRVn-rA@usadatanet.net>,
"Pop" <nobody@devnull.spamcop.net> wrote:
> Hi,
>
> Comments, responses inline:
>
> "SQLit" <sqlit@qwest.net> wrote in message
> news:ymOef.59$I14.872@news.uswest.net...
> :
> : "Pop" <nobody@devnull.spamcop.net> wrote in message
> : news:FZWdnYjExod0PebeRVn-rw@usadatanet.net...
> : > Hello all,
> ...
> : > I can measure:
> : > Volts rms, Current rms, Watts, Frequency, Power Factor, VA
> and
> : > time.
> : > I can calc my cost per kWH from my utility bills.
> : >
> : > Where I get lost is the PF (Power Factor). I was surprised
> to
> : > find PF down in the ranges of 50 to 80% on many appliances; I
> : > expected much higher. Anyway:
> : > I know 1,000 W for one hour is 1 kWH.
> : > But ... for cost calculations, how does the PF affect that?
> : >
> : > Clarifications would be most appreciated!
> : >
> : > Here's the kind of things running around in my head that
> perhaps
> : > someone could also clarify for me:
> : >
> : > If I consume 1 kWH over one hour, with a resistive load, then
> I
> : > have to pay for 1 kWH of power. Right?
> : > Then in two hours I'd have to pay twice that amount for
> power;
> : > it follows logically.
> : >
> : > But, what if I get the 1 kWH measurement at the one hour
> point,
> : > but ... the meter indicates the PF is 50%.
> : > Am I going to pay for half, one, or 1.5 kWH's?
> : >
> :..
> : > Pop
> :
> :
> : A residential meter rate that charges for PF? That news to me.
> Where I live
> : the utilities do not concern themselves with PF for residential
> customers.
> : Please provide the make and model of the meter they have
> installed on your
> : home. I would like to look it up.
>
> Sorry; guess one could have read it that way. No, the meter does
> NOT charge for PF that I know of. The PF numbers, also, came
> from my meter. Niagara Mohawk of National Grid is my supplier
> and near's I can tell they don't mess with residential PF's. I'm
> just surprised as some of the measured PFs I am seeing is all.
>
> Our power meter's recently been changed to one of the newer modem
> types that "calls in" the usage over the power lines. Nothing
> unusual, I don't -think-.
> :
> : What are the specifics of the rate your on? Some of my
> commercial customers
> : get charged for PF. They base it on the 15 minute demand window
> that they
> : use.
> Standard Residential rate. Varies from ten to 11 cents per kWH,
> depending on whatever - no idea unless it's usage amounts. I'm
> using "real" cost, BTW; total bill divided by kWHs delivered.
> :
> : What are you using to measure PF with?
>
> I have a cheapie meter that reads Vrms, Arms, Watts, VA, freq, PF
> and kWH. It's just a cheapie P3 "Kill-a-watt" meter. PF's
> calculated by simply dividing VA by Watts inside the meter; I
> think that's the right way to do it anyway, isn't it? Just got
> it and just yesterday dug out all my old meters to check its
> accuracy, at least ballpark wise.
> I compared its readings to a couple old VTVM's I have hanging
> around, and a borrowed current probe and it's reasonably
> accurate, surprisingly enough, so I'm XXX-u-me-ing it's giving me
> ballpark, at least relative, usable results. It looks pretty
> reliably in the plus/minus 5%; I'm guessing it's about 2.5% high,
> best I can figure. Most of my equipment's out of cal now but
> they seldom ever needed much cal work when I was using them
> daily. My scope's shot so I can't do any real peak work on the
> wave form.
>
> So, what do I do? Still looking for answers to my previous
> questions. (';=]
>
> Pop
> :
> :
> :
| |
|
|
"Pop" <nobody@devnull.spamcop.net> wrote in message
news:FZWdnYjExod0PebeRVn-rw@usadatanet.net...
> Hello all,
>
> First time poster on this particular group; from the look of some
> of the posts this might be the right place to ask my question.
>
> Before anyone comments, yes, I have too much time on my hands
> ;-]. I'm in forced retirements, health issues, and am trying to
> save a couple of bucks.
> I'm in the US, far northern NY state to be exact.
>
> I can measure:
> Volts rms, Current rms, Watts, Frequency, Power Factor, VA and
> time.
> I can calc my cost per kWH from my utility bills.
>
> Where I get lost is the PF (Power Factor). I was surprised to
> find PF down in the ranges of 50 to 80% on many appliances; I
> expected much higher. Anyway:
> I know 1,000 W for one hour is 1 kWH.
> But ... for cost calculations, how does the PF affect that?
>
> Clarifications would be most appreciated!
>
> Here's the kind of things running around in my head that perhaps
> someone could also clarify for me:
>
> If I consume 1 kWH over one hour, with a resistive load, then I
> have to pay for 1 kWH of power. Right?
> Then in two hours I'd have to pay twice that amount for power;
> it follows logically.
>
> But, what if I get the 1 kWH measurement at the one hour point,
> but ... the meter indicates the PF is 50%.
> Am I going to pay for half, one, or 1.5 kWH's?
>
> While I understand intellectually what PF is, I'm confused trying
> to figure out how I'm charged for it on a residential service (no
> load caps, etc. as industrial power requires). I think it's not
> knowing what the electric meter measures (or displays) vs. the
> meter readings from my meters that are confusing me. Google et
> al, even my own power grid folk are no help in getting a handle
> on this that I can understand fully.
> Over the period of a day/week/month/year, the error, depending
> on what I do or don't do with PF could become rather large, as in
> plus/minus 50% for my example.
>
> Thanks in advance for any assistance,
>
> Pop
Typically, residential kWh meters measure delivered and used kWh. They
don't care about and don't measure power factor.
There are, of course, special situations where a utility might install a
meter that measures PF; but that would be obvious when you look at the meter
itself.
If your house has a low power factor because of motors or whatever, the
utility eats the cost of delivering the VARs (volt amperes) to you.
But the utility has an economic incentive to keep the power factor on their
system as high as possible. Why push power around that nobody pays for? So
they will monitor system power factor and perhaps install capacitors in
areas where it is low.
It's best, however, to correct the power factor as close as possible to the
load that is causing it to minimize line currents Otherwise, the excessive
current will increase the line losses (so-called I^2 R losses).
TKM
| |
|
| Hmm, that makes sense; thanks.
"Rowbotth" <rowbotth@telusplanet.net> wrote in message
news:rowbotth-BD8841.19250416112005@news.telus.net...
: In your case, PF is not power factor. It think it might be a
multiplier
: to do with the PT and CT ratio built into the meter. (It has
been a
: while, but from my memories of what they tried to teach me
about
: metering, I think this is true...)
:
: PF either means that what you read is 0.5 of what you used, or
what is
: used is 0.5 of what is read. I forget which.
:
: The easiest way is to look at your bills. They may (mine do)
give you
: the date when the meter was read. This probably happens the
same day
: every month - more likely if the meter calls in the number, and
a
: machine does the calcs.
:
: Anyway, you want to figure out when this date is and then next
month go
: write down the number on the meter, at both the start and end
date of
: the "metered Month". If the difference between the two numbers
is what
: your power company charges you for consumption, then you know
what the
: PF means to you. Not much.
:
: But if you have to adjust the number you calculate to get what
you are
: billed on, then you now have clarification and understanding.
(Well,
: about this, any way!)
:
: Have fun. (Oh, you got the theory of calculating PF from VA
and Watts
: down pat. Well done!)
:
: H.
:
: In article <r-SdnTvke9MMQObeRVn-rA@usadatanet.net>,
: "Pop" <nobody@devnull.spamcop.net> wrote:
:
: > Hi,
: >
: > Comments, responses inline:
: >
: > "SQLit" <sqlit@qwest.net> wrote in message
: > news:ymOef.59$I14.872@news.uswest.net...
: > :
: > : "Pop" <nobody@devnull.spamcop.net> wrote in message
: > : news:FZWdnYjExod0PebeRVn-rw@usadatanet.net...
: > : > Hello all,
: > ...
: > : > I can measure:
: > : > Volts rms, Current rms, Watts, Frequency, Power Factor,
VA
: > and
: > : > time.
: > : > I can calc my cost per kWH from my utility bills.
: > : >
: > : > Where I get lost is the PF (Power Factor). I was
surprised
: > to
: > : > find PF down in the ranges of 50 to 80% on many
appliances; I
: > : > expected much higher. Anyway:
: > : > I know 1,000 W for one hour is 1 kWH.
: > : > But ... for cost calculations, how does the PF affect
that?
: > : >
: > : > Clarifications would be most appreciated!
: > : >
: > : > Here's the kind of things running around in my head that
: > perhaps
: > : > someone could also clarify for me:
: > : >
: > : > If I consume 1 kWH over one hour, with a resistive load,
then
: > I
: > : > have to pay for 1 kWH of power. Right?
: > : > Then in two hours I'd have to pay twice that amount
for
: > power;
: > : > it follows logically.
: > : >
: > : > But, what if I get the 1 kWH measurement at the one hour
: > point,
: > : > but ... the meter indicates the PF is 50%.
: > : > Am I going to pay for half, one, or 1.5 kWH's?
: > : >
: > :..
: > : > Pop
: > :
: > :
: > : A residential meter rate that charges for PF? That news to
me.
: > Where I live
: > : the utilities do not concern themselves with PF for
residential
: > customers.
: > : Please provide the make and model of the meter they have
: > installed on your
: > : home. I would like to look it up.
: >
: > Sorry; guess one could have read it that way. No, the meter
does
: > NOT charge for PF that I know of. The PF numbers, also, came
: > from my meter. Niagara Mohawk of National Grid is my
supplier
: > and near's I can tell they don't mess with residential PF's.
I'm
: > just surprised as some of the measured PFs I am seeing is
all.
: >
: > Our power meter's recently been changed to one of the newer
modem
: > types that "calls in" the usage over the power lines.
Nothing
: > unusual, I don't -think-.
: > :
: > : What are the specifics of the rate your on? Some of my
: > commercial customers
: > : get charged for PF. They base it on the 15 minute demand
window
: > that they
: > : use.
: > Standard Residential rate. Varies from ten to 11 cents per
kWH,
: > depending on whatever - no idea unless it's usage amounts.
I'm
: > using "real" cost, BTW; total bill divided by kWHs delivered.
: > :
: > : What are you using to measure PF with?
: >
: > I have a cheapie meter that reads Vrms, Arms, Watts, VA,
freq, PF
: > and kWH. It's just a cheapie P3 "Kill-a-watt" meter. PF's
: > calculated by simply dividing VA by Watts inside the meter; I
: > think that's the right way to do it anyway, isn't it? Just
got
: > it and just yesterday dug out all my old meters to check its
: > accuracy, at least ballpark wise.
: > I compared its readings to a couple old VTVM's I have
hanging
: > around, and a borrowed current probe and it's reasonably
: > accurate, surprisingly enough, so I'm XXX-u-me-ing it's
giving me
: > ballpark, at least relative, usable results. It looks pretty
: > reliably in the plus/minus 5%; I'm guessing it's about 2.5%
high,
: > best I can figure. Most of my equipment's out of cal now but
: > they seldom ever needed much cal work when I was using them
: > daily. My scope's shot so I can't do any real peak work on
the
: > wave form.
: >
: > So, what do I do? Still looking for answers to my previous
: > questions. (';=]
: >
: > Pop
: > :
: > :
: > :
| |
|
| ....
: Typically, residential kWh meters measure delivered and used
kWh. They
: don't care about and don't measure power factor.
:
: There are, of course, special situations where a utility might
install a
: meter that measures PF; but that would be obvious when you look
at the meter
: itself.
That's good; maybe I'll ask the PSC too & see if they respond.
National Grid doesn't seem to want to respond. The meter has
nothing, nada, other than a house-label with ID numbers, none of
which look like anything recognizable. The display area shows
nothing but usage digits; if there's anything else there it's
covered up and not visible. They have lots of data online about
reading the wheels and other stuff printed on the meter, but
nothing for their digital displays. Progress I guess.
:
: If your house has a low power factor because of motors or
whatever, the
: utility eats the cost of delivering the VARs (volt amperes) to
you.
I've been surprised at just how low the PF seems to be, actually,
but of course I'm doing it on an item by item basis so ... who
knows? Other than light bulbs, there really isn't much in a
house anymore that's not going to have a PF of some measurable
kind since almost everything else is an inductive load but none
of it's a constant duty cycle.
Any idea how low a PF is "LOW" to the utility? I've seen
things to make me suspect it's in the single-digit range.
:
: But the utility has an economic incentive to keep the power
factor on their
: system as high as possible. Why push power around that nobody
pays for? So
: they will monitor system power factor and perhaps install
capacitors in
: areas where it is low.
Interesting idea: I hadn't thought of that. I'll have to look
next time I pass the power station & see if I can tell if there
are caps there. Our part of the grid's fed from a plant about
ten miles from here.
:
: It's best, however, to correct the power factor as close as
possible to the
: load that is causing it to minimize line currents Otherwise,
the excessive
: current will increase the line losses (so-called I^2 R losses).
Thanks,
Pop
| |
|
|
"Pop" <nobody@devnull.spamcop.net> wrote in message
news:ssOdnRCPxfAxJOHeRVn-vw@usadatanet.net...
> ...
> : Typically, residential kWh meters measure delivered and used
> kWh. They
> : don't care about and don't measure power factor.
> :
> : There are, of course, special situations where a utility might
> install a
> : meter that measures PF; but that would be obvious when you look
> at the meter
> : itself.
>
> That's good; maybe I'll ask the PSC too & see if they respond.
> National Grid doesn't seem to want to respond. The meter has
> nothing, nada, other than a house-label with ID numbers, none of
> which look like anything recognizable. The display area shows
> nothing but usage digits; if there's anything else there it's
> covered up and not visible. They have lots of data online about
> reading the wheels and other stuff printed on the meter, but
> nothing for their digital displays. Progress I guess.
>
> :
> : If your house has a low power factor because of motors or
> whatever, the
> : utility eats the cost of delivering the VARs (volt amperes) to
> you.
>
> I've been surprised at just how low the PF seems to be, actually,
> but of course I'm doing it on an item by item basis so ... who
> knows? Other than light bulbs, there really isn't much in a
> house anymore that's not going to have a PF of some measurable
> kind since almost everything else is an inductive load but none
> of it's a constant duty cycle.
> Any idea how low a PF is "LOW" to the utility? I've seen
> things to make me suspect it's in the single-digit range.
> :
> : But the utility has an economic incentive to keep the power
> factor on their
> : system as high as possible. Why push power around that nobody
> pays for? So
> : they will monitor system power factor and perhaps install
> capacitors in
> : areas where it is low.
> Interesting idea: I hadn't thought of that. I'll have to look
> next time I pass the power station & see if I can tell if there
> are caps there. Our part of the grid's fed from a plant about
> ten miles from here.
> :
> : It's best, however, to correct the power factor as close as
> possible to the
> : load that is causing it to minimize line currents Otherwise,
> the excessive
> : current will increase the line losses (so-called I^2 R losses).
>
> Thanks,
>
> Pop
If you have mostly resistive loads (electric stove, incandescent light
bulbs, electric heaters, etc.) then it's unlikely that you have a low power
factor measured at your meter. Your meter, by the way, sounds like a simple
kWh meter but with a digital read-out, so you are not paying for any
electricity that you don't actually use.
Electrical loads that cause a low power factor include refrigerators, heat
pumps, a/c units and just about anything that has an electric motor. New
culprits are switching power supplies such as those used in computers; but
they are strange since the PF is dynamic (not strictly a capacitive or
inductive load).
I'll guess that the "mystery" of your low power factor is due to meters that
don't read "true rms" values. Most meters don't and it really counts if the
house load has wall-box dimmers, switching power supplies or other
electronic devices.
TKM
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"TKM" <nomail@no.net> wrote in message
news:59aff.119839$zb5.49020@bgtnsc04-news.ops.worldnet.att.net...
:
: "Pop" <nobody@devnull.spamcop.net> wrote in message
: news:ssOdnRCPxfAxJOHeRVn-vw@usadatanet.net...
: > ...
: > : Typically, residential kWh meters measure delivered and
used
: > kWh. They
: > : don't care about and don't measure power factor.
: > :
: > : There are, of course, special situations where a utility
might
: > install a
: > : meter that measures PF; but that would be obvious when you
look
: > at the meter
: > : itself.
: >
: > That's good; maybe I'll ask the PSC too & see if they
respond.
: > National Grid doesn't seem to want to respond. The meter has
: > nothing, nada, other than a house-label with ID numbers, none
of
: > which look like anything recognizable. The display area
shows
: > nothing but usage digits; if there's anything else there it's
: > covered up and not visible. They have lots of data online
about
: > reading the wheels and other stuff printed on the meter, but
: > nothing for their digital displays. Progress I guess.
: >
: > :
: > : If your house has a low power factor because of motors or
: > whatever, the
: > : utility eats the cost of delivering the VARs (volt amperes)
to
: > you.
: >
: > I've been surprised at just how low the PF seems to be,
actually,
: > but of course I'm doing it on an item by item basis so ...
who
: > knows? Other than light bulbs, there really isn't much in a
: > house anymore that's not going to have a PF of some
measurable
: > kind since almost everything else is an inductive load but
none
: > of it's a constant duty cycle.
: > Any idea how low a PF is "LOW" to the utility? I've seen
: > things to make me suspect it's in the single-digit range.
: > :
: > : But the utility has an economic incentive to keep the power
: > factor on their
: > : system as high as possible. Why push power around that
nobody
: > pays for? So
: > : they will monitor system power factor and perhaps install
: > capacitors in
: > : areas where it is low.
: > Interesting idea: I hadn't thought of that. I'll have to
look
: > next time I pass the power station & see if I can tell if
there
: > are caps there. Our part of the grid's fed from a plant
about
: > ten miles from here.
: > :
: > : It's best, however, to correct the power factor as close as
: > possible to the
: > : load that is causing it to minimize line currents
Otherwise,
: > the excessive
: > : current will increase the line losses (so-called I^2 R
losses).
: >
: > Thanks,
: >
: > Pop
:
: If you have mostly resistive loads (electric stove,
incandescent light
: bulbs, electric heaters, etc.) then it's unlikely that you have
a low power
: factor measured at your meter. Your meter, by the way, sounds
like a simple
: kWh meter but with a digital read-out, so you are not paying
for any
: electricity that you don't actually use.
:
: Electrical loads that cause a low power factor include
refrigerators, heat
: pumps, a/c units and just about anything that has an electric
motor. New
: culprits are switching power supplies such as those used in
computers; but
: they are strange since the PF is dynamic (not strictly a
capacitive or
: inductive load).
:
: I'll guess that the "mystery" of your low power factor is due
to meters that
: don't read "true rms" values. Most meters don't and it really
counts if the
: house load has wall-box dimmers, switching power supplies or
other
: electronic devices.
:
: TKM
Hmm, informative and useful. I hadn't considered the issue of
non-sinusoidal current drains either; good point. I'm glad that
point didn't show up earlier. I'd have gotten even confuseder
then <g>!
It's been an interesting thread; thanks to all who contributed.
Pop
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