About six months ago I bought an Anker set - a portable battery pack and some folding panels. A buddy of mine got basically the same thing, but Ecoflow. He lives in a condo, has a balcony, and can hang his panels there to charge the pack; my options are a little more constrained (3 story house with a couple hundred sq ft concrete "yard", with light blocked most hours of the day by the next house.)

I haven't gotten much use out of my set, but his plan was to run his desktop off it, which sounded very doable. All in all probably not quite the same as Germany (I guess their kits don't need a battery or plug into the wall or something).

Not the part where they plug the panels into a wall outlet. In the US getting the permits for grid tie is a huge expense and hassle so it would make no sense to do it for just a couple of panels. You need permission not only from the local government, but the power company, and possibly an HOA.

If you did this you would buy some Bluetti or similar power bank to charge off of the panels and use that power to run lights or maybe a mini-split heat pump so you can launder your energy savings through not having to run your home's grid-tie heat pump as much.

To do exactly what they’re doing in Germany would be illegal, or perhaps merely would make your utility very mad. It’s something like an 800w inverter that plugs into a wall socket. One issue for the US is that you don’t have access to both hots on one plug in a typical receptacle. Not a dealbreaker but one of many reasons you shouldn't import a German one and try and modify it for US use.

Just in my van -> RV conversion. ;-)