Yes, the power adapter (12VDC, 2.5A) is fine. If you want to double check, you can use a multimeter to measure the voltage, the polarity should be center positive, side negative (this is the most common type). DC-powered OpenSprinkler can accept any DC voltage in the range of 7.5VDC to 12VDC, with a minimum of 1 amp output current. More than 1 amp (such as 2.5 amp) is totally fine, and it allows you to open mutliple valves at the same time, but is not necessary if you only ever run one or two valves at the same time.