Regular solar panels have 3x3 size and generates 100kW, so (100 / (3x3)) = 11.11kW per tile.
Advanced are 4x4 and 200kW, (200 / (4x4)) = 12.5kW per tile.
12.5 / 11.11~= 112.5%, 12.5% is too small increase to even bother with upgrading.
Also 4x4 are probably harder to place in grid with substations.
I think this should be rebalanced. Either all solar panels should be 3x3 or advanced solar panels should generate more than 200kW.

I also made this calculation, and wondered about it.
However, I dont think this is a very big problem, because you save standard resources. But I agree, its more a prestige building than really an upgrade.
If the Mk 2 Solar Panal had 250kW instead of 200kW it would be fine.

Thanx, we'll improve it