I don't believe they are UL certified, but Dumfume sells 3.6kwh (300ah-12v) lifepo4 batteries for $320. 15 of those would get you 54kwh for <$5k. Might be tough to be anywhere near that point for UL certified only, though.
It’s an NEC violation (and also incredibly reckless) to connect electrical equipment that has not been tested by a NTRL. [0]
No inspector will sign off on a non-listed piece of electrical equipment, especially for a homeowner.
I repeat, do not connect electrical equipment to your home’s electrical distribution network unless it is tested by one of the labs listed in the link below, especially if it is hardwired.
That's 50KWH of battery, plus the 10.8KW of solar, inverters, etc., all for $17K. That system is microgrid (not grid following) capable; so, you can run it during a blackout. The switchover is pretty good, too, so you don't need a second backup system.
If I had to recommend in all in one kit, this september 2025, I would recommend an EG4 kit from Santan Solar. At brief glance they appear to be a stronger value and is from a company with a pretty strong customer service record. This is not sponsored in anyway.
Ya, the OP is not telling the truth. One there isn't a "variety", second they aren't UL listed at that price. I've spent months researching this space for an off grid setup and these are the two best setups direct from China from a cost standpoint for 15 kWh. Neither are UL listed:
It would be multiple batteries totaling that. Stock and prices are constantly changing but RUiXU, EG4 and EcoWorthy are widely available brands with UL listed options. Will Prowse's website has a page dedicated to code compliant batteries and there are several long lists and excel sheets on the diysolarforum.