That page, although it was written only four months ago, is citing LCOE figures from 02021, when mainstream solar panels cost €0.25 per peak watt. Now they cost €0.100 per peak watt—see https://www.solarserver.de/photovoltaik-preis-pv-modul-preis.... Power electronics and batteries are also enormously cheaper now. Also, note that the LCOE numbers it cites are for the US, where most of the costs stem from the US government's anti-renewable-energy policies such as punitive tariffs, policies that are not in effect in Germany.

That page also undermines its credibility by citing the hypothesis that the low cost at the time (which it acknowledges was already down to 36% of the number in 02012) was because the "massive wave of imports" was "subsidized by China’s central bank"; if that were the case, you'd expect that once China owned the world's solar market, the prices would have gone back up to reflect the true costs of manufacturing the panels, so that China's central bank could stop hemorrhaging money in these subsidies. Instead, the prices have continued to drop. They've dropped as much in the four years since that report as they had in the nine years before it. And, if you read the Department of Commerce filings justifying the "anti-dumping" tariffs, you will find that the arguments being made about "subsidies" are transparently ridiculous; the supposed "subsidies" include the fact that Chinese panel manufacturers pay their workers less than Turkish electronic assembly workers, and the fact that they have good public infrastructure to use.

It also incorrectly claims that solar panels need to be replaced after 25–30 years (that's just the warranty period) and that doing so would add US$20–30/MWh to Lazard's US$36/MWh LCOE, which is an obviously an arithmetic error that's off by orders of magnitude.

But its central claim, that rooftop solar is much more expensive than utility-scale solar, is actually true. The reason for this is mostly that rooftop solar requires much more labor and enjoys poorer economies of scale. You have to pay someone to design custom racking for your particular roof and a custom inverter and battery storage system for your house, pay someone to climb up on your roof and possibly die, pay for permitting and inspection, etc. You can find a more detailed breakdown of "turnkey installed cost" in SEIA's Solar Market Insight Report https://www.seia.org/research-resources/solar-market-insight....

However, all of these factors are completely the other way around for balcony power plants. You don't climb on the roof; you walk out onto the balcony. You don't design custom racking; you buy an off-the-shelf retail product. The same thing for battery storage, if you buy a system with battery backup. Instead of spending thousands of dollars, you just hang the solar panel off your balcony like a potted plant and plug the plug into the outlet. The engineering is being done at the factory for a mass-market product, not for your house or for a single utility-scale solar farm. So you're spending less in engineering and permitting and construction costs than a utility-scale solar farm would, not more.

There is one way in which balcony power plants are worse than rooftop solar: they are at terrible angles, so they don't get much sun. But that just means you get less power, maybe two or three times less than you'd get in an optimally-designed utility-scale plant. That matters much less now that solar modules are so cheap.