I’m really wondering what your situation is then. That sounds like a worst-case scenario. Do you have a tree in front of your panels? Are you only running electrical equipment at night? 10-15 cents a day in summer either means your electricity is damn cheap, the panels don’t generate much for whatever reason, or you are not using it when it is being generated.

Also for 500 Watt peak a battery does not make much sense, if at all it should be a small battery to buffer peak demand (the refrigerator compressor turning on or other similar high-power short duration load, but that’s definitely not worth it unless you are trying to go off-grid, but that’s a completely different topic.). That’s obviously gonna decrease your ROI.

But just straight up saying that you doubt whether balcony solar is making its money back is detrimental to the whole cause, especially since there are enough people out there using it that are easily getting their money’s worth.

I feel the 500kw balcony vertical install won’t cover 20% of a household.

That depends on your household, but again - since you were emphasizing ROI - the balcony solar not being able to cover a lot of your consumption means their ROI is better! This does not mean, that one shouldn’t install bigger systems, I’m just trying to convince you, that balcony solar does have a very reasonable ROI in most cases.

What kind of refrigerator are you running? Around 100 Watt should be enough to run a decently sized refrigerator. Solar panels are somewhat forgiving when it comes to the proper angles, 100 Watt peak should be easily achievable with an 800 Watt setup, even if they are very badly angled. Sure, not 24/7, and maybe not all year round, but that’s not the goal.

Also, since you focused on ROI, that’s the nice thing about small installations - basically all the energy generated is directly used by you, meaning it directly replaces energy you would have had to buy otherwise. This is the more expensive kind of energy, and you “make” more money with that as if you sold the electricity. The ROI of solar power (for everyday people) goes down the bigger the system gets, as you won’t be able to use all the peak power when it is generated.

Completely agree, saying that solar is heat sensitive when talking about not being able to power ACs is pretty far out there.

Adding to what you said, ambient temperature only has a slight impact on solar’s efficiency. Solar’s efficiency usually mainly goes down due to self-heating which is due to higher irradiance. So in some sense they are less efficient because they generate more power.

However your example numbers are way off, solar panels generate much more peak power during summer than during winter, they aren’t close to being similar (depending on lattitude, but I guess that’s a given when talking about “summer” and “winter”).

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And the other part that should not be overlooked is that there tends to be some correlation between hot weather and long sunshine, which can also be seen in the plot. So not only is peak power of solar higher during the time when heatwaves are more likely, they also generate power longer.