What "Green" actually means: (from an article about a similar model)
The device sports master/controlled outlets that cut down on energy consumption by automatically shutting down power to unused peripherals, such as printers, scanners and speakers when your Mac is in sleep mode. The master outlet is designed to sense current drawn by connected equipment, typically a computer. When your Mac powered down or goes into sleep mode, the master outlet automatically shuts down the controlled outlets, which consume power even when the computer is off. By cutting power to these "dark loads", the APC Back-UPS ES 750 can provide a combined savings of US$40 per year on average as compared with competitors' models, according to Joe Loberti, senior vice president, Home and Distributed Systems, APC. source