What is the best UPS for a critical power load?

On-line UPS systems provide the ultimate level of power protection. They provide a digitally generated sinewave output to their connected loads and are classed as Voltage and Frequency Independent (VFI) of the incoming mains power supply. On-line UPS also feature a built-in automatic bypass to ensure safe failure-to-mains of the connected load(s) if the UPS inverter is overloaded or develops an internal fault condition.