How to read meters

[S-Murt]

I am a new member I stumbled on this site as I searched the net for information on how to read my meters. Thank you to the administrator for accepting me…..

I installed solar on my home back in October 2022 and am taking meter readings daily to validate accuracy between the Solar meter, Solar Edge (SE), and the electric company meter. I’ve been taking meter readings daily for 4 months and enter it into a spreadsheet. Through analyzing the data against my bills I have made assumptions on how the electric meter works but have been unable to validate the assumption. I’m hoping someone here can help as it is possible, I’m missing a calculation.

• SE meter is easy. It’s one number so I subtract the past days reading from my daily measure and get the KWHs generated for that day.
• My Electric Company meter has two number. One number is KWHs used and the other is KBH Excess Solar energy. So, I’m assuming if I add KWH used and KBH excess Solar it seems that the result should be a number that matches what my SE meter shows as being generated.
• Actual RESULT is, as mentioned above, a number that is 20 to 28% lower.

So before I go have a conversation to get someone to come evaluated meter performance is there a calculation I’m missing or is there usage occurring that neither meter will ever show?

Appreciate any and all education

Steve

[Mike 134]

• My Electric Company meter has two number. One number is KWHs used and the other is KBH Excess Solar energy. So, I’m assuming if I add KWH used and KBH excess Solar it seems that the result should be a number that matches what my SE meter shows as being generated. That is incorrect. First number is what you buy from the power company, the second is what you sell back to the power company after powering your house's requirements. That's why they don't add up because a portion of the power you generate goes to supply your house.

[J.P.M.]

I am a new member I stumbled on this site as I searched the net for information on how to read my meters. Thank you to the administrator for accepting me…..

I installed solar on my home back in October 2022 and am taking meter readings daily to validate accuracy between the Solar meter, Solar Edge (SE), and the electric company meter. I’ve been taking meter readings daily for 4 months and enter it into a spreadsheet. Through analyzing the data against my bills I have made assumptions on how the electric meter works but have been unable to validate the assumption. I’m hoping someone here can help as it is possible, I’m missing a calculation.

• SE meter is easy. It’s one number so I subtract the past days reading from my daily measure and get the KWHs generated for that day.
• My Electric Company meter has two number. One number is KWHs used and the other is KBH Excess Solar energy. So, I’m assuming if I add KWH used and KBH excess Solar it seems that the result should be a number that matches what my SE meter shows as being generated.
• Actual RESULT is, as mentioned above, a number that is 20 to 28% lower.

So before I go have a conversation to get someone to come evaluated meter performance is there a calculation I’m missing or is there usage occurring that neither meter will ever show?

Appreciate any and all education

Steve

What information or guidance did your POCO have to offer when you contacted them and enquired about how to read their meter ?
I'd start at the source (your POCO) and assume nothing before I got into conversations with others, either on a paid basis or otherwise.

Many meters are the same. Many are different. Without more details, folks will have a hard time understanding your questions.

When you get your POCO's meter info from the POCO straightened out, expect a small discrepancy between any PV monitoring totals and what the POCO meter totals show.
FWIW, my meter shows (among other info) :
- The meter reading.
- What I've sent to the POCO.
- What the POCO has sent to me.
All in kWh and all totals since the meter was installed.

After 10+ years of daily meter readings and recording and more, I estimate my system monitor thinks my system's output is about 0.0053 higher than my POCO meter.

See what your POCO offers in the way of guidance on how to read your meter. It's the best place to start.

[littleharbor2]

POCO = Power Company.

[S-Murt]

JPM, I’ve been avoiding the discussion with POCO until I was clear how everything worked and I had validated my assumptions. This was one of my steps....
Given Mikes response and yours I now see that a conversation with POCO would have probably changed the purpose of my reading to one of validating monthly data in the bill instead of trying to determine the accuracy of meters. I homed in on a “bad meter” due to something that happened during system startup.

So, Based on what I read from both you and Mike I’d probably conclude that the variance I’m calculating, between POCO readings and the SE Meter readings, is actually part of the Daily KWHs used by my home.

Based on learnings from the above two comments I think the spreadsheet changes to:

METERs
Solar Edge (SE)		POCO			Calculations			Solar Proof
Solar Generation		Excess Solar	Purchased Energy		Difference SE Solar Generation Minus POCO Excess Solar	Per Day Household KWH Used		Difference Plus Excess Solar
82 KWH		51 KWH	12 KWH		82 - 51 = 31 KWH	12 +31 = 43 KWH		31 + 51 = 82 KWH
					My guess is that this is what I was considering by just taking meter readings	I was thinking my home was only using 10 to 14 KWH per day. This seems more realistic

If this is accurate understanding, then my work is done. However, JPM you mentioned “After 10+ years of daily meter readings and recording and more, I estimate my system monitor thinks my system's output is about 0.0053 higher than my POCO meter.” What numbers do you use to identify that you output is .0053% higher?

[SunEagle]

Remember a watt is calculated based on a voltage times and amperage. If the voltage used in multiple calculations is different then the resulting kWh value can also be different. So the Solae Edge system calculation could be different then the POCO's which could be the reason for not being equal.

[Mike 134]

Just an FYI about "revenue grade meters" before you go looking for "missing watts". Their accuracy has to be +/-0.5% or better so with one meter perhaps reading +0.5% high and the other -0.5% low just like that your numbers are 1% different reading identical loads.

[bcroe]

I would not expect everything to come within 1% in a field setup. For
one, every measurement of voltage and current will have some error,
and the power factor measurement is another possible source of error.
Even the loss in wiring enters in, your meter sees the voltage entering
the system, but voltage at another nearby point will be slightly different.
Here that shift hit 9V, lately it has been held to 2V.

I would expect the PoCo meter to have the least error.
Bruce Roe

[J.P.M.]

JPM, you mentioned “After 10+ years of daily meter readings and recording and more, I estimate my system monitor thinks my system's output is about 0.0053 higher than my POCO meter.” What numbers do you use to identify that you output is .0053% higher?

I'm out in the desert just now doing some other stuff. I'll respond when I get back to n. county San Diego.

J.P.M.