Hey, man! Congrats on your solar panel system! This is a nice topic. I've been talking recently with other Hivers (@stefano.massari and @homesteadtlt) about it.

I also want to install something like this on the roof of my house in the next two years in order to get more decentralized and become less dependant on the centralized electricity-producing companies in my country/area. I've been thinking about installing 9 solar panels (325Wp) which will generate about 3KW. Such kind of solar panel system (the cheapest one) is about 3000 Euro. But, my highest consumption of electricity is usually during the winter, (to heat the house), and in particular during the night. So, if the solar panel system generates electricity during the daytime I have to store somewhere this electricity. For this, I need an accumulator (or whatever it is called in English) to store/keep the generated electricity there and use it during the night.
So, my question is if your installation/system includes such kind of accumulator? Because you mentioned in your post that you have this 'Battery Backup'? Is this where you store the electricity or do you simply sell the excess electricity to the grid (the company which operates in your area)?