If your electricity goes down, unless you have a backup power supply nothing will operate anyways. There is no way to control your lights, a/c’s or other smart devices in your home because they all require electricity to operate. If your internet goes down, your entire system will continue to operate as normal on your local home network. That means inside your house everything is still connected on your main router and continues to talk to each other, allowing you to control what you need. Once you leave your home network and try to access the system from outside your home, that is when things will not be operable from the outside world since the internet is down at your space.