It is being sent into the general electrical network of the house/flat, where it lightens the base load. There is a maximum of 800W that you are allowed to feed into your home network. Anything bigger is subject to different rules and approval by the electrical service provider.

800W aren't a lot, but it can half the cost of your washing machine run, make your fridge power free and let a PC idel or a NAS run. These balcony solar generators usually make back their costs within 5-8 years if you calculate what you'd otherwise pay for the electricuty.