Talk to the customer and see what he wants, and what he is willing to pay for. Even though my veterinarian is not required by code to have backup power he installed it because he is very concerned about the possibility of losing power during surgery (lighting, cauterizer, anesthetic & breathing apparatus), losing heat and lighting and sump pump during an extended power outage, etc. And he is concerned enough about employee and animal safety to go beyond code requirements in those areas, but maybe not quite as far as a hospital for humans would have to go.