4 12V 200AH deep cycle lead acid batteries cost $1552 on Amazon and hold as much energy in practice as a 100AH 48V LFP battery which last 15 years, minimum, and only costs about 6% more up front. (Not linking to specific batteries in order to not shill for them, but do a little searching for 100AH 48V 4U server rack LFP batteries on youtube, and you will find dozens of tutorials.) Quality inverters last 30 years, not 10.
Are these people TRYING to light money on fire? Are they fronting for someone by trying to make solar look impractical? Or are they just stupid?
Over the past 20 years I have noticed this tendency among a subset of people people in the environmental movement. Some people loved solar power only when it was expensive and small scale. A future world powered by solar once evoked images of cozy little villages, bicycles, deglobalization, handmade wooden toys, and a slower pace of life. Now that solar power is inexpensive and scalable, it's unappealing to people who value the cozy aesthetic more than they value meeting quantifiable IPCC emissions targets.
"For example, if I omitted the battery storage of my solar installation, my system would become about 10 times cheaper: ..."
and then goes further along this interesting line of reasoning...
And the only inverters we know will last 30 years had to have been made in the 90s …
Lead acid is much more dangerous than that, IMO, due to the potential offgassing.
For me at least the storage is about 1/3 of the cost of the system and I'll likely have to replace it once (probably with Sodium Ion since that is taking off and $50 a KWH) and a new inverter and there is no way it costs even half the total system install over the lifetime.
Also, where did you buy your inverters in 1993? I've used about six different brands on various deployments and ten years is about right for MTBF there. I sure wouldn't trust a fifteen-year-old inverter to handle 3500VA continuous, and god forbid there's a spike...
If you want something better and brand name, you'll pay more. Sometimes, significantly more.
It still doesn't make sense to use lead acid for off grid, deep cycle or not. UPS systems still use them because lead acid loves to stay charged at 100% and not drop below half, which is fine for UPS that are intended to run only during occasional power failures.
LFP batteries also last for thousands of cycles and are safe, probably safer than lead acid.
This is a common misunderstanding. The lithium batteries used for off-grid and RVs are not the kind you're thinking of. They are LiFePO4, and far less susceptible to thermal runaway than, for example, an average laptop battery.
To be clear: batteries are still not cost effective relative to a grid connection, but everyone who has an off grid system goes for LiPO for a reason.