My conversion from watts to VA was off pretty significantly. I am now using the maximum designed wattage as outlined in APC specifications for each UPS. The SC1500 that I intended to use will be overloaded but it is more economical to get three of these LS700 units instead! The values for the computers are estimates based on the PSU in each unit (value can only go down from there) as well as the 1A regulated 12V supply consumption. I don’t think we need the monitors themselves on backup power (it would be cool for them to flicker when we transfer from internal to external power and vice-versa.