Wifi not guaranteed during load shedding.

My mother has subscribed for rain internet services last year and so far she didn't have any problems. We bought a backup power system for her that cost us a lot so that she can watch tv and have wifi, but she is having problems with the wifi sometimes during load shedding. Rain told me that they cannot guarantee that the wifi will work during load shedding as their towers uses electricity! What about backup during this time of load shedding? I have Telkom fibre and don't have these problems. I am going to cancel my rain subscription for her and subscribe for telkom fibre.