Hi,
I recommend not to use yellow science for research of this good idea, because with yellow science you can get fusion reactor. So no portable solar panel needed at all. 500x RGB science would be fine in my opinion.
Peace

I'm taking that back, seems like the portable fusion reactor is a prerequisite for that so seems like you had specific plans and purpose with that.

The original plan was to have tiny modules to fill the empty gaps in your equipment's inventory.
In 0.16 the modules had even less power (30kW = 3x vanilla) and were also unlocked after the fusion power equipment.
Your premise makes sense though and 500 RGB seems like a reasonable price, so i'm actually considering to change it.