This has been an issue over the years. Even when when the configs allow more solar panels. For example: Average 2.06KW solar power input, Consumption 180 watts. Leave the planet for more than a day, come back and the solar caps are drained! Regardless of the number of caps and scenario. And the plants, they stop growing when the PF is not active. Oh sorry, edit: this being with dedicated server. Not tested in any other circumstance. Edit again: seams on leaving then planet when the sun is up, come back days later caps are full. Leave the planet when the sun is down, come back days later the caps are drained.
Yea, the offline power use and genneration is a problem, but i don't think it is high on the priority list for eleon i'd like it to be reworked too, also the constructors should keep running and when finished switch to standby (now they keep using power but stop producing as far as i can tell) or catch up like autominers... a easy fix for eleon would be to use the averagy power income from solar instead of the current value. and a real fix would be to also have the plants grow and the constructors produce (or catch up)
I suppose that the real fix would be separate the energy / production rate from the circumstance of if the playfield is loaded or not. Time passes on not loaded playfields too, these should not be in a "cryogenic chamber" or stasis field when you leave the playfield. But this is complicated to program, on many games, frequently, the events are not managed for unloaded content / areas. Here it is happening something very similar.