Its weigh can vary between 16kg (36V1S) and 17kg (36V3S) depending on the configuration of the bike. This weigh is calucated with motor and battery but without any accessory (racks or fenders).
Even with this weigh, it is lighter than any other bike on the market. Even when you don't use the battery, the bike is still easy to ride. You do note depend on the battery, what is even better for the planet :-)