Measuring self consumption


I’m sure this shouldn’t be too difficult, but I’m trying to work out how to measure solar self consumption. I have a standard setup for the My Solar app:

I essentially need to do [solar output] - [exported solar] but can’t get the numbers to work.


Have you set it up as a “Type 1” or a “Type 2” installation?

Bear in mind that our convention is for import (both from the grid and from your PV) to be positive and export to the grid to be negative, so

should actually read [solar output] + [export] to take the sign of the export into account.

It’s a type 2 system. I did originally write [solar output] + [export] but thought it might be confusing :slight_smile:

So ct1 is the Grid import/export, and ct2 is the Solar (import).

Let’s say you do this on the CT2 Inputs processing. After what you have there now (use_kwh):

Reset to ZERO (start afresh)
+feed [ct1]
Allow negative (this “adds” only the {negative} export)
+feed [solar]
Log to feed [solar_self_consumption]
Power to kWh

I think that will give you the power and accumulated energy from the PV, plus the negative component (i.e minus the exported part) of the grid power/energy.

It’s recommended to use “+feed” rather than “+input” to better align the readings in time.

Thank you! The bit I hadn’t worked out was the ‘reset to 0’. Just need some sun now to check it’s working…

Oh wait, ‘allow negative’ seems to be allowing positive values through:

I think you may have the order of your feeds wrong. Solar feed should be last as per Roberts example.

Thank you, I was being an idiot. Thought the ‘allow negative’ would be applied to the line following it for some reason.