Power meter question?

[powerup]

When my system was completed the utility company replaced my meter with an Itron brand solar meter.
It has one 5 digit display for Kwh and the dot indicator which displays which way the power is going.

The day my solar went on line the meter reading was 00136 and as of today 3 1/2 wks. later 00048.
My question is if or when it goes backward more to read all zeros will it then show a Negative number or just all 9's?
Is this the number the utility company uses to figure your bill reading?

[peakbagger]

These days there are a lot of different meters out there. Most utilities have multichannel meters so there are no negative values. The utility did change out a mechanical meter when I first installed solar long ago with new single channel Itron and it did indeed show negative values. That is not a guarantee as some meters are configured to record power in either direction as positive.

The utilities billing system could not deal with negative values so I got hand calculated bill every month for a few years until they got their computer billing to deal with it.

[bcroe]

The utilities billing system could not deal with negative values so I got
hand calculated bill every month for a few years until they got their computer billing to deal with it.

I wonder if that is why, my bills were so irregular for my first years of net metering? The spinning disc would
have done the job if they cancelled the display reversing gear. But they put in a meter read by radio, which I
could not read at all, to get rid of the meter man. Now after years it has been replaced again, and the bills
come like clockworks. I do not really trust what they may be up to, but my (was theirs) spinning disc is now
remounted in the basement as a check on them. Bruce Roe

[J.P.M.]

I wonder if that is why, my bills were so irregular for my first years of net metering? The spinning disc would
have done the job if they cancelled the display reversing gear. But they put in a meter read by radio, which I
could not read at all, to get rid of the meter man. Now after years it has been replaced again, and the bills
come like clockworks. I do not really trust what they may be up to, but my (was theirs) spinning disc is now
remounted in the basement as a check on them. Bruce Roe

Bruce: Have you done any comparison(s) between what the POCO meter says and what your meter says ?

[bcroe]

Bruce: Have you done any comparison(s) between what the POCO meter says and what your meter says ?

J. P. M., Yes each month they list increased (or decreased) KWH reserve. I can compare that to my record
for the same days. I record it daily and know what day they took their reading. I expect to be a small
percentage dis advantaged each month, because my meter does not cover the original dist box circuits,
mostly slightly used rooms and other very light loads. Bruce Roe

[J.P.M.]

J. P. M., Yes each month they list increased (or decreased) KWH reserve. I can compare that to my record
for the same days. I record it daily and know what day they took their reading. I expect to be a small
percentage dis advantaged each month, because my meter does not cover the original dist box circuits,
mostly slightly used rooms and other very light loads. Bruce Roe

Understood. Thank you.

One more if I could: Any SWAGs on differences the meters would show if measuring the same amount of energy or power ?

[bcroe]

Understood. Thank you.

One more if I could: Any SWAGs on differences the meters would show if measuring the same amount of energy or power ?

I cannot actually directly measure power on mine, unless I took a stop watch to the rotation time. There is
no direct power readout on the PoCo meter, just those arrows indicating direction of flow. The monthly
bill is my only (almost) direct means of comparison. Bruce

[J.P.M.]

I cannot actually directly measure power on mine, unless I took a stop watch to the rotation time. There is
no direct power readout on the PoCo meter, just those arrows indicating direction of flow. The monthly
bill is my only (almost) direct means of comparison. Bruce

Thanx again.

WAY back when, I got a lot of appliance power draw #'s with the old rotary meter and a stopwatch. Last time I did that was 2006 when I figured out the power draw for the water heater resistance element and the A/C on this house. The method/procedure was a bit clunky and involved but cheap and accurate. Worked great for me.

[bcroe]

I once observed the disc doing 34 rpm or 2040 revolutions per hour, while putting away about
14 KWH (each hour). So I concluded about 145 revolutions about equaled a KWH. That is
probably good to 10%, have not tried to do better.

The original problem, was not getting a PoCo bill till weeks late, or even none one month. So
it was hard to know my remaining past summer reserve as winter was finishing. Now I can
line it up once a month and watch it crank down day by day. Bruce Roe

[J.P.M.]

I once observed the disc doing 34 rpm or 2040 revolutions per hour, while putting away about
14 KWH (each hour). So I concluded about 145 revolutions about equaled a KWH. That is
probably good to 10%, have not tried to do better.

The original problem, was not getting a PoCo bill till weeks late, or even none one month. So
it was hard to know my remaining past summer reserve as winter was finishing. Now I can
line it up once a month and watch it crank down day by day. Bruce Roe

Bruce, FWIW, I found this method in a book called "Home Remedies" which is a print of proceeding of a conference on residential retrofit I attended in 1980:

There is/was a meter constant on the face of my old rotary electric meters in about the 1 or 2 o'clock location.

Perhaps you rotary meter has one in about the same place.

I don't recall what it was numerically for any of them, 7.3 something out to 4 decimals sticks in my mind. the actual calcs are here someplace. Let me know if it's any use and I'll root around in the archives around here. As I think I do recall, it worked out that the meter constant was how many Wh of energy went through the meter for one revolution of the meter disc.

The method to get an appliance's steady state power draw or energy usage went something like this: I'd shut off as many things in the house as possible, most importantly, intermittent loads like fridges/freezers. Then, I'd sit there and watch/count 10 or 100 or maybe 1,000 disk revs on the meter and measure/record how long it took for those revs w/ a stopwatch. I'd then fire up the appliance I wanted to measure the power draw/energy use on and the repeat the process. Then, I'd calc the difference in energy/power use.

Obviously, kill-a-watt meters are easier/faster, but they weren't around back in the day, and this method works for 220 V appliances like electric resistance fired tank type water heaters or A/C units and other 220 V stuff as well as being a way to help snoop out vampire loads. A lot of the same data can be had with the newer meters, but depending on how many revs are counted per trial, using a rotary meter and knowing the meter constant can be more precise than using a digital meter. The old meter on this house meter was supposed to have 0.50% accuracy by the ITRON spec sheet. I believe the current GE meter is the same.

As an example : My old electric resistance element fired tank H2O heater drew 4,520 W on several trials with the old meter and the described method. My 5 ton A/C unit drew a steady state 6,120 total W, +/- 5 W or so including the blower motor which draws a pretty steady 842 or so W after startup transients. The blower motor now has a dedicated kill-s-watt meter that I use to isolate air conditioning electrical usage, but that's another topic.

As for your situation of not getting bills, and FWIW, I read/record my POCO meter's reading 1X/day about 10 minutes after I get up. I compare what I calc for usage and generation by the day, and sometimes by the hour if I think I need/want to against what the POCO thinks and it's almost always a dead nuts match. I still check, but I don't need the POCO bill except to check them for billing errors.

Add: To the OP's original question, FWIW. my new (as of 08/2013), digital POCO meter worked backward and at 1 excess kWh generation showed 999999. My POCO billing is based and calc'ed on a tare difference at the billing date/time of the meter readings. Your meter/POCO may be different but my guess is it's similar.

[bcroe]

Bruce, FWIW, I found this method in a book called "Home Remedies" which is a print of proceeding of a conference on residential retrofit I attended in 1980:

There is/was a meter constant on the face of my old rotary electric meters in about the 1 or 2 o'clock location.

Perhaps you rotary meter has one in about the same place.

I don't recall what it was numerically for any of them, 7.3 something out to 4 decimals sticks in my mind. the actual calcs are here someplace. Let me know if it's any use and I'll root around in the archives around here. As I think I do recall, it worked out that the meter constant was how many Wh of energy went through the meter for one revolution of the meter disc.

The method to get an appliance's steady state power draw or energy usage went something like this: I'd shut off as many things in the house as possible, most importantly, intermittent loads like fridges/freezers. Then, I'd sit there and watch/count 10 or 100 or maybe 1,000 disk revs on the meter and measure/record how long it took for those revs w/ a stopwatch. I'd then fire up the appliance I wanted to measure the power draw/energy use on and the repeat the process. Then, I'd calc the difference in energy/power use.

Obviously, kill-a-watt meters are easier/faster, but they weren't around back in the day, and this method works for 220 V appliances like electric resistance fired tank type water heaters or A/C units and other 220 V stuff as well as being a way to help snoop out vampire loads. A lot of the same data can be had with the newer meters, but depending on how many revs are counted per trial, using a rotary meter and knowing the meter constant can be more precise than using a digital meter. The old meter on this house meter was supposed to have 0.50% accuracy by the ITRON spec sheet. I believe the current GE meter is the same.

As an example : My old electric resistance element fired tank H2O heater drew 4,520 W on several trials with the old meter and the described method. My 5 ton A/C unit drew a steady state 6,120 total W, +/- 5 W or so including the blower motor which draws a pretty steady 842 or so W after startup transients. The blower motor now has a dedicated kill-s-watt meter that I use to isolate air conditioning electrical usage, but that's another topic.

As for your situation of not getting bills, and FWIW, I read/record my POCO meter's reading 1X/day about 10 minutes after I get up. I compare what I calc for usage and generation by the day, and sometimes by the hour if I think I need/want to against what the POCO thinks and it's almost always a dead nuts match. I still check, but I don't need the POCO bill except to check them for billing errors.

Add: To the OP's original question, FWIW. my new (as of 08/2013), digital POCO meter worked backward and at 1 excess kWh generation showed 999999. My POCO billing is based and calc'ed on a tare difference at the billing date/time of the meter readings. Your meter/POCO may be different but my guess is it's similar.

Those are quite legitimate ways of getting power info. I do not see such a number on 3 meters here,
but my estimate amounted to 6.9WH per revolution, consistent with yours that is likely more accurate.
With stuff going on in 3 buildings, I never tried to use the house meter to check appliances. But I was
able to connect a Kill-A-Watt meter to each individual circuit (about 60) by removing the regular breaker
and inserting one with the meter attached. For 240VAC I wired in another spinning disc meter and kept
a record for days or longer.

My PoCo may have a way to get current use directly on line, I and my ancient Apple have not
succeeded in accessing it. The CURRENT KWH COUNT is not on the bill, clearly my disc will
just go like an old car from 99,999 to 00,000 in either direction, I have written software that has
no issue dealing with that.

Looking up at blue sky today, that disc is really moving. Love to hear the comments when people
see it. When the bill comes I subtract the reserve from my meter reading at the billing day, and
get the anticipated meter number when I run out of reserve. Each month the exhaustion point
moves just a bit since a bit of energy does not go thru my meter, but that can be estimated to be
really accurate. Bruce Roe

[J.P.M.]

Those are quite legitimate ways of getting power info. I do not see such a number on 3 meters here,
but my estimate amounted to 6.9WH per revolution, consistent with yours that is likely more accurate.
With stuff going on in 3 buildings, I never tried to use the house meter to check appliances. But I was
able to connect a Kill-A-Watt meter to each individual circuit (about 60) by removing the regular breaker
and inserting one with the meter attached. For 240VAC I wired in another spinning disc meter and kept
a record for days or longer.

My PoCo may have a way to get current use directly on line, I and my ancient Apple have not
succeeded in accessing it. The CURRENT KWH COUNT is not on the bill, clearly my disc will
just go like an old car from 99,999 to 00,000 in either direction, I have written software that has
no issue dealing with that.

Looking up at blue sky today, that disc is really moving. Love to hear the comments when people
see it. When the bill comes I subtract the reserve from my meter reading at the billing day, and
get the anticipated meter number when I run out of reserve. Each month the exhaustion point
moves just a bit since a bit of energy does not go thru my meter, but that can be estimated to be
really accurate. Bruce Roe

From one eccentric to another, understood.

Respectfully,

[foo1bar]

My question is if or when it goes backward more to read all zeros will it then show a Negative number or just all 9's?
Is this the number the utility company uses to figure your bill reading?

Mine rolled over to all 9's, and kept decreasing.
My guess would be that will be the case for yours, but there are many different meters out there, so there might be another brand (or version within a brand) that does it as a negative number.
Doesn't really matter.

Yes, that number on the meter should be the number the POCO uses for billing

[PugPower]

I recently got my main panel upgraded when I got my solar installed. My meter was reset to 000000 and then rolled back to 999999 and decreased from there. I'm with SDGE and I am a little disappointed not see negative numbers. Just thought it would be neat.

[bcroe]

I recently got my main panel upgraded when I got my solar installed. My meter was reset to 000000 and then rolled back to 999999 and decreased from there. I'm with SDGE and I am a little disappointed not see negative numbers. Just thought it would be neat.

I set up my own meter so it reads UP whenever I am adding to KWH reserve. Spins backwards
and counts DOWN when taking some back. More pleasant. No need to zero it. Bruce Roe