Kris, there are at least two types of UPS systems. One that will come on when there is a power failure and therefore is in standby mode, the other is a system where the UPS is actually outputing power all the time via the batteries and they are constantly being charged. This later is preferred in the data processing business as there is no cut over time from outlet power to battery backup. I'd prefer this design as the equipment you're using, never knows a power outage occurs. Naturally, this later system is a little more expensive. Therefore, you'll need to decide your threshold of pain.
Steve
