Hi again
I thought for a while and finally found what is "strange" with the definition given by jayc (sorry bro, it is a friendly disagrement). In AC and DC the definition of power is the same P = V*I, the point is that in AC we are talking about the rms value of the voltage, which is the case of V = 220 volts. Looking at the last equation on the above explanation, it refers to Vo which is the peak voltage, if you replace Vo = sqrt(2)*V, you will find that P= V*I,
cheers
Sal