Hybrids are becoming more and more topical thanks to the Tesla Powerwall. The basic concept of a hybrid system is to store electricity that is generated during the day by your solar electricity system so you can use it in the evening when the sun has gone down. Hybrid systems are not designed to store days and days of electricity but rather enough electricity to last you through the night. It is called a hybrid system as you are still connected to the grid but have batteries to store power. So if it rains for 4 days you will be getting your electricity from the national grid like most other people.