Dear SlopppyEngineering
My friend and me are playing multiplayer on Factorio 0.13.20 and with BioTech 0.1.3.
The Electric Network hovers at ~12.1, the Entity update at ~3.5. We currently have ~1500 Photosythesis Panels placed. Every other value when we enable "Time Used Percent" in the F4 menu in "Update" sits at 0.0[some numbers]
When we toggle BioTech in the mods option and load the same save, Electric network sits at just above 0 (0.01 or so) as does the Entity Update. With BioTech enabled we average a value of ~20 in "Update" and without it a value of ~2.

None of the Photosynthesis Panels are connected to the electric network, so they power themselves in daytime and are unpowered during night time. We both went and disabled all of our mods 1 by 1 in different combinations (Biotech, Orbital Ion Cannon, Power Armor MK3, Day Night Extender). The lag only disappeared when we disabled BioTech 0.1.3.

We will try updating to Factorio 0.14 with the mods and let you know the results.
Best regards
4plains

We updated our mods and Factorio for to the latest build (0.14.14).
No changes to the performance numbers. The bug is still there.

I suspect that's because it has some hidden elements for doing the day/night cycle. I'm going to test if removing the day/night stuff reduces lag.

Thanks for looking at the issue.

I think the only way is to remove all electric components. Each panel now has it's own electric network. If that is removed, all panels will need electricity from the main grid.

One way to "fix" it is to have bigger yield per placed entity.
I'm not suggesting you change the crafting speed of the normal panel though. I would suggest (if that is easily doable) "photosynthesis panel arrays" (could be a researchable tech).
For example a 3x3 array. They would take up the space of 9 panels (and you could probably reuse the normal panel sprite 9 times). It would be 9x yield (crafting speed 3 instead of 0.33) for the same impact in terms of lag.
Maybe arrays can go from 2x2 to 5x5 and one could research the different arrays increasing in size. The 5x5 array reduces the lag per produced sugar solution by 96%.
My suggestion for the different array crafting recipies would be the standard panel in however many numbers is needed (9 for the 3x3), some low density structure, and some wooden flooring.
The flooring and density structure because the arrays have to be held together by something.

Greets and best regards

PS I have no idea if what I suggest really is easy to implement. I have limited experience in coding. It doesn't fix the underlying lag issue, it however changes how many entities are needed to sustain production.

To keep that under control, there are three tiers of photosynthesis panels. The second tier is x5 the performance and material cost of the first tier panel. The third tier is x25 for the same surface area.

The latest update removed the internal solar panel. The lag seems to be caused by each panel creating it's own grid, and each separate grid needing extra CPU time.