That you can only charge to 80%. You still have to finish it off at home on a slow charger.
The best battery system available for solar home systems right now, however, is this one:
The reason this system is so important is simple: It's an independent system that doe NOT feed power back into the power grid.
Tesla's solar roof system was supposed to power it, but it never came into being. That doesn't mean though that you can't run this system off of any solar panel installation.
The reason it's important is this:
Used to, the government required power companies to pay solar users for power that they fed back into the grid. It made solar power a great investment because not only did it cut power usage down, but by selling excess power back to the grid it cut demand on plants and that cuts power costs and coal usage on a huge level.
But the power companies sued claiming that it was "their" grid and as such customers that fed power back into "their" grid should actually have to pay for the privilege.
The power companies (and their lobbyists) won.
So all of a sudden, people who had solar systems wired to their main boxes and meters that fed power back into the grid all of a sudden started getting HUGE bills for actually feeding power they harvested but weren't using and feeding back into the grid.
That's where this system came into play. It was (and with the exception of 2 others still is) the only solar battery system that runs ENTIRELY independent of the power grid while still utilizing the main power panel.
It's a brilliant system. Sadly, it's not on Musk's list of things to tweet about as they don't sell it for a huge profit, so they mostly sit in the warehouse gathering dust along with the rest of gigafactory 2.
