Solar customers: Recognizing the "Daytime dip" and how it might impact your Sense numbers

For those who may be wondering why this might be relevant to them: I’ve spent some time, now that I have a couple days off, confirming this does seem to affect device detection. A couple appliances and a set of lights that are recognized before/after daylight didn’t seem to show up when we’re generating power during the day.

There’s some beta feedback Sense should be taking seriously - solar customers will surely be at a disadvantage when it comes to consistent appliance detection.

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[quote=“NJHaley, post:2, topic:403”]
There’s some beta feedback Sense should be taking seriously - solar customers will surely be at a disadvantage when it comes to consistent appliance detection.[/quote]

I tried an experiment yesterday, and it does seem like my Sense monitor is underreporting the solar production by about 2.5%. Now, 2.5% may not seem like a lot, but when you’re subtracting two large numbers to get a small number, a small percentage error in the large numbers can translate to a large percentage error in the result.

Yesterday my solar panels were generating about 7kW, with a small amount used in the house, and the remainder going to PG&E. Sense reported that the difference between the solar production and the power going to PG&E (i.e., the power used by the house) was 317W. I turned off the solar inverters, and the power used by the house as reported by Sense jumped up by 180W to 497W. That’s a 36% error in the reported power used by the house.

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Thanks for verifying, for a while I thought I was going crazy! Thanks for posting another relatively simple way to ID whether you’re affected.

And you’re right - the percentage may seem small but the raw values will add up to about 50kwh/mo in the summer time for me.

I don’t know about you, but except for perfectly clear days I see quite a bit of variation in my solar output as clouds and haze impact it. Thus, I don’t think I would be confident of the baseline with solar versus without it.

[quote=“NJHaley, post:4, topic:403”]
And you’re right - the percentage may seem small but the raw values will add up to about 50kwh/mo in the summer time for me.[/quote]

You are right, the absolute error is an issue, but I’m more concerned about how this affects device detection.

By identifying some of the power hogs, I hope to get my always-on load down to 250W.

Suppose in the summer the solar panels are producing 10kW. The always-on load is taking 250W, and the balance of 9.75kW is going to PG&E.

But if the Sense monitor is reading the solar production 2.5% low, it will be registering 9.75kW solar production, 9.75kW going to PG&E, and therefore zero consumption in the home.

I think the Sense monitor algorithms will have trouble reliably detecting loads if it’s reading zero when actually 250W is being used.

Thinking further, to 11kW production and 200W always-on, the error in the sense reading will be greater than the entire load it’s trying to measure. That can’t be good.

Ding ding ding! In fact, your always on turns to zero, which is something I started noticing as our days started getting longer and less cloudy:

Prior to a couple weeks ago, we were pretty cloudy since right around Xmas (when I started up my replacement Sense device), not making too much more than we were using. Back then I posted a thread winning “always on” value: So what is your MINIMUM power usage? 249 here for a big house - #2 by NJHaley Now I’m at zero :slight_smile:

I think this horse has been beaten - now to hope Sense makes strides to fix it.

Here are a couple of other examples of the daytime dip from my system.

In the first example of a daytime quiet time with no one home you can see I have a very stable usage pattern. The main usage is from a variable speed pool pump from which you can see a very clear tooth pattern normally. The tooth pattern is mainly from the variable speed motor switching speeds to adjust for the pool solar water heater. The interesting thing is to see the highly irregular pattern occur along with big solar fluctuations from passing clouds.

In the second example you see a more pronounced dip occur around 2:30 in what would normally be a very stable time period.

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Interestingly, yours seems to be more of a “blip” than a “dip.” While I would expect mine to rise when the sun goes behind a cloud, yours drops when production goes down.

Why it’s the opposite of mine is escaping me - do you have supply-side or load-side solar? Mine is load-side for what it’s worth.

I’ll take a guess that the difference of a blip versus a dip “might” have something to do if they had to do a software flip to account for a CT that was in the wrong direction. I was just looking at my system today based on what you are seeing and I am most definitely seeing consumption go UP when the solar goes DOWN due to a cloud. This is not good and they need to figure out what is going on here ASAP!!!

Here are a few pictures:

I’m curious about the software flip too, @Howard. As best I can tell, mine had to be “flipped” since my CT decals are facing my inverter, not my main panel.

For posterity, though, are you load or supply side solar? (ie is your solar feeding into the panel through a breaker, or is it going directly into the mains?)

My solar feeds through a breaker in my main electrical panel.

I tried the experiment of turning everything off in the house this afternoon.

The Sense monitor should therefore have been reading 0W. It actually showed negative power use: -78W.

The Sense monitor reported that the solar panels were producing 3146W. They were evidently producing 78W more than this at the time — about a 2.5% error.


As a new user, I am experiencing a problem that may be related, but not exactly the same. After 3 weeks and several problem reports my tracking solar arrays seem to be reporting OK but now my Mains power is way too high. The Mains readings seem to be 2X the solar power minus the actual power used off the Mains.
Are the Sense technical team looking at each “new” installation and tweeting the power reporting procesd?
Quick edit: Just took another look and one Mains leg is reporting almost all of the power from the two solar legs. Strange!

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I had a similar issue recently happen with my system where usage was about two times production minus reported consumption. They have to do a total reset of my system from scratch and wipe everything out. :frowning:

Wierd, I have solar, looking at my logs. I do not have this problem.

Do you have any details on your install? Sounds like you’ve got an enphase inverter - is it tied in as supply side or load side? Any specifics on how your cts are arranged?

Early adopters get snubbed again I guess :confounded:

If it’s something as simple as how it was installed or the Sense build, I wish they’d just say so. I’ve done just about everything I can to correct this, including a new unit; it’s ridiculous it hasn’t been fixed yet. This is honestly the most terribly supported smart device I have.

I do have enphase inverters, and it is tied in with the loadside. I’m
wondering if maybe the inverter is too close to the sense CT clamps.
Eletromagnetic interference maybe? Have an RF meter? I was an early
adopter as well, so I don’t think that’s the problem. I’ve had a few issues
but the sense team works them out fairly quickly, or fixes it before I
report them. Wondering if sense will need to create some sort of
calibration setting when this scenario presents itself.

I feel, based on some of the Sense team posts, that it’s a legitimate software-side problem related to a voltage calibration problem they pushed a fix for back around Xmas. I think the trouble they’re having is identifying who’s affected, based on their comments.

I know that one of their competitors has a setting that the end user needs to set dependent on what sort of inverter connection the user has, but I have a feeling this issue is a little outside of that. My nighttime measurements are dead on, it’s only when solar is involved that things get mucked up… unfortunately as the days grow longer, that has more and more influence on the reporting as a whole.

Ditto on your comment about the customer service!
They have the ability to manipulate the input phase parameters and get it corrected, apparently they lack the personnel (and they don’t appear to work on the weekend ). My solar status shows the correct power while the one leg of Mains shows almost all negative power.
For us Android users the Sense team really missed when they released an app update which crashed on screen rotation and then took almost a week to correct. I never saw anything from Sense acknowledging this, maybe I am looking in the wrong forum!