Not quite correct there Bob, you are using the old UK standard voltage of 240 volts to calculate from but in fact with the European harmonized voltage it is now 230v.
Yeah, I know that in reality it can still be 240 volts within the +- allowable error range but I just wanted to remind everybody not to forget and use the old value.
all the calculations done above have been done with the formula for Direct Current. ie- what you get from a battery. It is a reasonable rule of thumb if you want a quick and dirty calculation but not strictly accurate for AC- alternating current- ie what comes out of your sockets! Calculation of power for AC includes whether the load is capacitive or inductive or a combination of both. The phase shift through these loads affects the power calculation. Simply multiplying Voltage and Current in AC gives something known as Reactive Power