Net meter not accurately showing power sent to the grid.

[BFW577]

I have been thoroughly monitoring my electric panel consumption and solar production since my install in May. My Itron net meter seems to be not accurately measuring power sent back to the grid. It flashes 04 and 10 and shows what I pulled and sent to the grid. I have a Locus revenue grade meter installed between my SE5000 and the line side tap. On my inside panel I have a effergy whole house energy monitor that I have been using for 4 years and is extremely accurate.

Crunching the data on all three there is around 150kwh missing that should be showing on the net meter that I sent back to the grid. I realize that the net meter wont see what the panels are sending into the house and being used but the effergy sees that.

Has anyone every run into a bad net meter not accurately showing what was sent back to the grid. Makes me suspicious of my poco.

Here are some picture to get an idea on my setup. The effergy setup is not mine but is installed the same way.

[J.P.M.]

What approximate %age of your total consumption does the 150 kWh represent ? Revenue grade meters are usually and nominally +/*- 0.5 % of total reading. Others are available (for more $$) that claim +/- 0.2 %. Other meters are a crap shoot as you are finding out. To quote one of the mods several years ago, a man with two watches never knows the correct time. I've got a method that seems pretty good to compare one meter against another in a residential setting, but it requires shutting off (opening) all the breakers in the panel except the one handling the array, and carefully recording the off time and then comparing the before/after meter readings. Seems to give reasonable results.

[NEOH]

In the photo for the Efergy, I see ...
A = Amps C/T for L1
A = Amps C/T for L2
B = Transmitter
C = Meter / Display

Where is the connection to read the Voltage on L1 & L2?
If there is none then how is the Phase Angle computed?
How does the Efergy measure True-RMS Amps or not?

You said "The Efergy ... is extremely accurate"
"Extremely accurate" compared to what?

The website states, "... up to 99% accurate ..."
HUH?
That statement guarantees nothing.

[bcroe]

I would be most inclined to trust the revenue grade meter. Your level of error might be accounted for by failure
to properly account for power factor. The voltage must monitored and the power factor figured. Putting your
Itron on the same circuit as a revenue meter for a while might be a good test. Bruce Roe

[BFW577]

Not sure on the power factor but I believe my solaredge inverter monitors the voltage. I have one of those plug in killawatts and it shows my power factor at 1.0.

Prior to installing the solar it was pretty spot on when compared to my electric bills. My electric bill/meter would show700 kwh and the effergy would show like 702 or 698. Its accurate enough that if I turn on a 60 watt light bulb it shows exactly 60 watts coming on.

I rest the effergy and took readings at midnight last night and am going to monitor through the weekend.

[sensij]

Are you using the Locus or SolarEdge as your source of data for generated power. Can you compare the two? My guess is that SolarEdge is overstating the energy produced by 4% or so.

[NEOH]

I have one of those plug in killawatts and it shows my power factor at 1.0.

How can the Kill-o-Watt measure the Power Factor of the whole house at the Main Panel?


Total Error between the three devices?

Is the Itron PV Meter bi-directional?
Can the Itron PV Meter differentiate between "Power Generated" and "Power Consumed" by the Solar Edge?

8,400 KWH per Year = 700 KWH per month x 12 months
And you are off by 150 KWH per year?
That is less than 2% error between three different devices.

You stated that your Efergy wholehouse readings can be +/-0.5%

What if ...
a) The Efergy Wholehouse Meter is under-estimating KWH consumed by 0.5%
b) The Locus PV Meter is over-estimating KWH generated by 0.5%
c) The Itron Utility Meter is over-estimating NET KWH consumed by 0.5%

That is a Total Error of 1.5% between the three devices.

How often do you need to re-calibrate your devices to certify they are still +/-0.5% ?

Most digital meters are more accurate from 1/2 scale to full-scale and less accurate at the low end of the scale.

[CharlieEscCA]

And you are off by 150 KWH per year?

I think he was saying he's missing the 150 kWh between May and now ...

[NEOH]

BFW577
Post the four different KWH Values = ( Ending Reading - Starting Reading ) for the two Months from May to July ...
1) Consumption per the Efergy Meter ?
2) PV Production per the Locus Meter ?
3) Consumption from the Grid per the Itron ?
4) Production into the Grid per the Itron ?

I am very suspicious of the Efergy Meter because:
a) It does not measure voltage - it assumes 120v / 240v
b) It does not calculate the Power Factor.
c) It does not compute TRUE-RMS Amps

Did the line voltage increase?
Measure the line voltage during full PV output.

[BFW577]

BFW577
Post the four different KWH Values = ( Ending Reading - Starting Reading ) for the two Months from May to July ...
1) Consumption per the Efergy Meter ?
2) PV Production per the Locus Meter ?
3) Consumption from the Grid per the Itron ?
4) Production into the Grid per the Itron ?

I am very suspicious of the Efergy Meter because:
a) It does not measure voltage - it assumes 120v / 240v
b) It does not calculate the Power Factor.
c) It does not compute TRUE-RMS Amps

Did the line voltage increase?
Measure the line voltage during full PV output.

I just did 4 days of measurements. The Effergy in the past 4 years has been extremely accurate when compared to power bills I received. It's real time display will show a load turn on very accurately. If i were to turn on a 100 watt incandescent bulb it shows exactly a 100 watt increase. Based on my past experience its is very accurate.

So I took a reading of the Locus meter, the Itron net meter and the effergy. Waited 4 days an crunched the numbers. Looks like a 5-6 kwh difference on the net meter on power sent back to the grid. Here are the numbers

Initial readings.


Locus meter. 1284
Itron Net Meter. 10 (power sent) 907. 4 (power received) 550
Effergy. Reset to zero

4 days later

Locus meter: 1423
Itron Net meter 10 (power sent) 995 4 (power received) 607
Effergy 103kwh

I think I am not sure if I am doing the calculations correct.

Locus meter 1423-1284 = 139 kwh produced
I sent 88 kwh and used 57? The difference is 145?

[sensij]

What does Solaredge show as produced over that period?

[1423 - 1284] = 139 kWh produced - 103 kWh consumed = 36 kWh net export

[995.4 - 907.4 ] = 88 kWh energy exported
[607 - 550] = 57 kWh energy received
31 kWh net exported.

The ability of the effergy to accurately measure a simple resistive load like a light bulb is different than its ability to measure motor loads that have some power factor to them, like a compressor motor. I'm not saying it is or is not the problem, just that your example doesn't really tell us much about its accuracy.

[BFW577]

What does Solaredge show as produced over that period?

[1423 - 1284] = 139 kWh produced - 103 kWh consumed = 36 kWh net export

[995.4 - 907.4 ] = 88 kWh energy exported
[607 - 550] = 57 kWh energy received
31 kWh net exported.

The ability of the effergy to accurately measure a simple resistive load like a light bulb is different than its ability to measure motor loads that have some power factor to them, like a compressor motor. I'm not saying it is or is not the problem, just that your example doesn't really tell us much about its accuracy.

Just looked at the data. The locus meter shows 1449 kwh. Solaredge shows year 1.444 and total 1.480. Not sure on the difference as it was installed in May. Do they perhaps test them at the factory and that is why the total is higher?

I think you may have solved it. I do have a Carrier Infinity hvac system. Its a heat pump/ac with a variable speed compressor and blower. It regulates its output based on the hvac demand. I think the effergy has a 15 second update interval. Im starting to think it can't pick up on the surge when it kicks on or regulates the output. It pulls about 3.5 kwhs running at full output.