What size UPS do I need for a CCTV System?

Most CCTV camera and security systems have low power requirements and a UPS sized from 500VA to 2000VA (2kVA) is commonly installed to protect the system. To work out the size of uninterruptible power supply required, list the Amps or Watts required by each of the devices in the system, typically the AC/DC power supply for the CCTV cameras and the DVR/NVR recording device.