"Eyesore" is in your own opinion. What I've seen on balconies around here, anything covering them is a 50% chance of being an improvement — and unlike some acquaintances, I've not encountered balkon-FKK. And IMO they're a big improvement over, e.g. the AC units on the skyscraper walls of Manhatten.

I have balkonkraftwerk because they're a 60% return on investment, per year for 35 years, tax free and self-adjusting for inflation. By far the best (reliable) investment one can make.

That €350 is currently economically worth €7350 over their lifetime in reduced energy bills, tax free. The economics are so strong that it would be worth doing even if energy was 1/3rd the current price.