Any intelligent animal is fighting for its survival when feeling threatened. There's no reason to assume that a self-aware AI will be OK with us simply pulling the plug on it.
I'd like to think we could find some middle ground ebtween helpless surrender and imposing the death penalty on a sentient individual, both in moral terms and in terms of having some failsafe mechanisms, so that supplying electricity didn't allow for a takeover of the power grid or other doomish scenario.