Amazon addresses that in their report. Each UPS is fed by generator power and grid power. Because the UPSes had been forced to try to supply the grid, and becau

Amazon addresses that in their report. Each UPS is fed by generator power and grid power. Because the UPSes had been forced to try to supply the grid, and because they are giant spinning weights that you really don't want to go wrong and kill someone or destroy property, they did a safety inspection before powering them back up, which meant a delay before the facility could be supplied by generator power.