I think the way I am using it it will be ok.
I’m using the output (Solar max 0) as my solar production which will be monotonically increasing as it can’t go negative.
My Grid integrator will pick up the inverter self load at night.
Edit: is there a reason we can’t use outputs in outputs?
Is it to prevent circular references?
I needed to change these to (Solar max 0) as well. It would have been easier if I could have used the solar_prod output instead I had to replace (Solar) with (Solar max 0).