4. Backup power generators. Many places have backup power, especially in areas where seasonal outages are common (heavy snow, etc). Places like banks might, but they might also have systems in place where the vault is impossible to open without the power being on. Many places have battery backups for alarms (like jewelry stores), but they only last for so long. Police stations, fire stations, power companies, data centers, government installations concerned with emergency management (like FEMA), and the like, usually have back up power generation. The thing is that the backup power capacity is not unlimited, nor is the stored fuel. Business managers spend what they think is prudent for what they expect to happen – be that for a few hours or a few days.