Because a car amp is designed to run essentially off a car battery they require a a DC source, usually 12V. What you need is a power converter. You must be careful however:
Ohms law states that Power (w) / Voltage (V) = Current (A)
If you had a regular 1000w amp running at 240v it will draw 4.166 amps.
If you apply this to a 1000wamp running at 12v it will draw 83.33 amps.
Now this is a high current, and you must remember you are not going to be maxing out your system. Just remember that you cant simply cut the plug off of the nearest nokia charger and wire up a car amp, you will just melt the charger. It needs to be fused, and be wired with cable rated to take the current.
the impedence of the speakers used and number of channels used are also major factors in the final value of the current drawn by the amplifier. Im not goin into that though.
I wouldnt recommend using a car amp unless you use a car battery