The California Public Utilities Commission looked at the issue in detail in in Decision 08-09-014 September 4, 2008. The Commission looked at three options:
- No backup requirement.
- Four hours.
- Eight hours.
Following Hurricane Katrina, the US Federal Communications Commission determined (FCC 07-177, October 4, 2007), that telephone central offices must have a minimum 24 hours backup power and cell towers for mobile phones eight hours. However, it is not clear if this decision survived appeal.