Enphase Solar Input - Nighttime power consumption - workaround

Hi, new iotawatt user, I’ve just installed my device over the weekend - https://photos.app.goo.gl/wVhzcsgiitcyUiHj9

Once my Enphase solar system stops producing for the day, its starts showing 13-17W of consumption - but on the Solar input, whether or not this is the Envoy and a combination of the x26 micros i’m not sure. The same consumption also shows up the Envoy installer portal.
We are talking small numbers here but it is still throwing out the solar production numbers.

Anyone know of a way this can be stopped?

Some inverters consume standby power when not producing power. The default setting for the input is to automatically convert negative power values to positive. This is what appears to be happening here:


If this is a problem, you can check the “allow negative power values” box for the input. Then where you use the value in a script, use the max function to effectively suppress negative values:\

(solar max 0)

Understand that max and min are binary functions and result in the larger and smaller of the two operands. So if solar is -14, the function evaluates to -14 max 0 = 0.

If you are inclined to also measure the standby (negative) consumption of the inverters, you can use the min function:

(solar min 0)

to develop the negative value, and

((solar min 0) abs)

if you want it as a positive number.

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I just noticed the same issue. My solar comes into the main breaker panel on 2 hot wires, and I put a CT on each. Sometimes at night I see positive readings on one and negative readings on the other and I’m not sure what that means. If the inverter electronics runs at 120V, using 1 hot leg and a neutral, then it would make sense that just one leg is drawing power, but then I would expect the other to be zero. Here’s an example graph, where the sun is completely down.

My solar generation output is set to (PV_A + PV_B) max 0. Inverter Standby output is set to ((PV_A + PV_B) min 0) abs. And the grid integrator is set to Subpanel_A + Subpanel_B + EVSE_A + EVSE_B + Bidet_1 + Bidet_2 + Spa_A + Spa_B + Bath_Heater + Patio + Mini_Split - ((PV_A + PV_B) max 0).
The 2 PV inputs are both set to allow negative values, and the are oriented so that solar generation is a positive number.

I’m curious to know how much power my inverter is actually consuming at night. But currently I don’t think it’s setup right. Do I need to use an integration for PV_A and PV_B ?

@overeasy do you have any advice on how to set this up, based on my above post? I want the solar generation to read zero at night, and track the inverter consumption separately.

Are you sure you have the CTs oriented the right way?
What does it look like during the day?
You said it only used 2 hot wires, does it also have a neutral wire from the inverter?

You are also dealing with numbers that are quite small and might just be induced noise from another circuit. What else was going on from 17:22 to 17:42? Do you have an electric water heater or heat pump that might have been running at that time?

Bottom line is that readings of a couple of Watts for a load like that are not accurate. The current is probably around 10 mA and it’s probably crazy reactive.

The CTs are oriented so that solar power production is a positive number during the day. It all looks good during the daytime — inverter standby output is zero, and solar production shows a nice curve.

Bob, if the load is really that tiny then we can just call it zero. But I can’t figure out what formula to use to make the sensor to read zero at night.

Short answer is that there is no way to reliably implement a low cutoff with scripts. Inverter standby power is typically negative and is easily filtered with a “max 0” function, but that doesn’t eliminate a positive standby reading.

I’ve looked at a couple of these lately, and it appears that the combination of very low standby power coupled with a very reactive component can appear as very low positive power due to normal lsb error in the ADCs and AC zero cross detection.

One way to possibly deal with it, given that the reading is so small, would be to shift the low positive value negative and use the “max 0” function.

Generation = ((PV_A + PV_B -1) max 0)

The result should be a low cutoff of 1 Watt. There is a side effect that any power will be one Watt less than actual. That is pretty much insignificant with respect to your daytime generation. None of this will have any affect on the kWh generation total.

If one Watt doesn’t sufficiently eliminate the nightime standby, you can raise the threshold by subtracting 2 or 3 instead of 1.

That makes sense, I’ll try that. Thanks.

I have a similar issue as the topic of this thread. I have a grid tied solar setup. Mine has a red and black wire with a neutral. (240v) I’m only monitoring the black wire and doubling it to get the total. This works great and very closely matches what the inverters report for generation and also jives with the utility meter every month. What I’m seeing at night is about 18 watts an hour and it shows up as solar output. My first move was to change the CT so it allows negative values thinking it was seeing micro inverter consumption at night but even with being set to allow negative values, it still shows positive output from the array (9.62kw) at night. I’ve went a step or two further in my trouble shooting. My solar feeds into my panel thru a 240v double pole breaker on my my side of the meter. I’m also monitoring the mains coming in from the meter. At night, I got the house load super stable and opened the breaker from the solar. The solar output dropped to zero but there was also zero change on the mains. I was thinking if the solar output was real, I’d see a 9 or 18 watt increase on the mains (the solar CT is doubled) but there was nothing. I’m glad it’s not showing up on the mains but it looks like the 18 watts an hour does affect the monthly total a little. It must not be there during the day when the panels are producing. The iotawatt is off roughly 5kwh a month and only on the solar CT. Not a huge deal but if there’s a way to make it better, I’d definitely give it a go.

I think if you move the CT from the black wire to the red wire, you will see negative values at night.

Just swapped it… It was actually on the red wire and now that I think about it, I think I swapped wires a while back to see how that affected things. It’s now showing negative and the arrow on the CT is pointing in the same direction as power flow if the sun was shining. I’ll check it tomorrow when the sun is shining and see if the number becomes positive or more negative.

Because your voltage reference is only one leg of the split phase, the two will always be opposite and have different signs. I’m pretty confident this is the standby loss of your inverter and will reverse when the dawn breaks.

I’m thinking I started out with the CT on the black wire. The solar was installed about 6 months ago and LOTS has happened since then clouding my memory. I want to say I’ve tried this before. If the numbers go further negative when the sun is shining, I’ll have to change the CT around so the arrow is pointing opposite of power flow? I don’t want to reverse it in configuration. Would that mean the CT is connected to the opposite leg as the voltage reference? And if I do have to reverse the orientation, that would make the nighttime wattage be positive again. If I’m remembering correctly, I think this is why I moved the CT to the red wire. The arrow on the CT was in the correct direction and the readings were correct without using the reverse function. I originally installed the CT on the black wire and did it when the sun was shining. I was looking at the iotawatt in real time when I clipped it on and it showed negative so I turned it around with the arrow pointing the “wrong” direction for daytime power flow. Then on that first night, I saw “output” when there shouldn’t be. That’s when I allowed negative values. My memory may not be entirely accurate. The CT is currently on the black wire with the arrow pointing from the array towards the meter and it’s currently showing negative 18 watts. I have 26 panels and 26 micro inverters. Since the output is doubled, it looks like the inverters are using 9 watts an hour. I can go on my solar app at night and see data from the inverters so I would agree they’re using power at night. But why didn’t the mains see it when I opened the solar breaker? The solar CT went to zero when the breaker was open but the mains never changed. Not one watt. I went to lengths to make sure the house load was near perfectly stable.

Let’s wait and see what the dawn brings. There is another possibility that we can explore.

It’s running further negative.

OK, that’s not it. For now you can either put it back on the other wire or, easier, just check reverse in the CT setup to go back to positive solar power.

At this point, I’d like to take a look at what is going on with the neutral wire. Is it possible that you could put a 50A CT on it?

I can pull the CT from the black and put it on the neutral unless you require a CT on the black while a CT is on the neutral.

Just trying to eliminate a remote possibility. let’s leave that for now.

Can you go back a few days with Graph+ to a time during the night when the +18 was being reported? Select out (just highlight on the graph) a period of an hour or less so the intervals are 5 seconds, then for the solar plot as Watts, VA, PF and VAR all on the same plot. Click CSV at the bottom and post the plot along with the first dozen or so lines of the CSV.

I think this is probably a low power reactive load issue and may want to take a cycle sample tonight.