Does this graph make sense in terms of PV versus grid supply

I hope the attachment shows :slight_smile:

Last night I bit the bullet and connected the Grid and PV CT clamps onto their respective cables. I then connected them to my emontx v3 which had been pumping empty data up to the site

One of the things I noticed (given that I have only been collecting data for less than 24 hours) is that the solar feed shows as negative - is this correct? Looking at the graph to me it does but I may be wrong.

What is the “best” unit for measuring the grid and PV feeds? W? kW ? kWh?

Thanks for you comments. This is a major step forward for this project and even the wife is interested (but she was a PV convert before I even knew her)

If it makes sense to you, it’s correct. However, our convention (and it is only that), is all power inputs to your premises are positive, so the algebraic sum is the power consumed (and of course, the convention naturally transfers to energy, because time can’t go backwards). So if you stay with what you have, you’ll need to remind everyone what your convention is.

All are “best” when used for the purpose for which they are suited.

What do you want to know? Is your primary concern power or energy? Do you actually know which units relate to which, and how they relate to one another? Do you want to relate directly to the units your supplier’s meter reads and your bill shows, or are you concerned with consumption or generation of the moment?

Many thanks for that. One more question on a related subject - can I get the graph to auto refresh?
#I have looked for an option but can’t find it.


The Graph graph does not refresh, however the realtime visualisation that you can have on your dashboard does.

As you’re a new user, I’m going to risk suggesting an approach, which is how I got started 5 years ago now.

I think, because you are showing negative values, that you have the AC voltage sensor, which can tell the direction of the flow so you know when you are exporting. This is good.

In my opinion, the best way to get started is to use the App, My Solar.
This requires 6 feeds from 2 CTs, and it’s all beautifully documented in Solar PV - Guide | OpenEnergyMonitor.
The only thing is those instructions are for emonPi not emonTx but wherever you see emonPi, just think emonTx.

You will of course have to follow the conventions @Robert.Wall mentioned above but that really just means turning your CT round on the Solar so it faces the other direction and records positive by default.

Good luck, happy to help if you don’t get it.

Thank you very much everyone who has responded. It is quite probable the CT sensor is the wrong way around because at the time I connected them my only goal (given it was dark and rainy( was to see if I could run the cables through we wall - I didn’t expect to be able to complete the job as easily as I did so I will go back and revisit the polarity

I wi read that document later when work doesn’t get in the way

Thanks again everyone.

Once again thanks to everyonee who has offered assistance to me on this. I know have the data going up to (the easy bit) and back down into influxdb (I still have an issue with a couple of feeds returning a unit type of C but I am investigating that

So my next question (yes’ I have googled) is what are the E1 and E2 feeds for ? Are they cumulative representations of P1 and P2 and if so where are they documented?



A search here should have revealed the answer - I have answered this at least once before. They are the accumulated Energy values.
(EmonTx values and calibration question)

I doubt it is documented for the sketch you’re using, but the new EmonTxV34CM_rfm69n sketch has the identical output format, and that’s documented here: The emonPiCM

Thank you very kuchen Robert

Because I wanted autorefresh and the ability to correlate individual applicances (measured voa energy aware smart plugs) I linked to influxdb running on home assistant and the results are shown below.

My next challenge (nothing to do with emoncms) is to correct the units of measurements on the graphs nut I know the values are correct.