I am just curious about how much kilowatt required for B747 , B 777, A340 or smaller B737, A320 ?
The 747 has 4 60 KVA (54 kilowatt) generators. On a 747F, a nominal load is around 20% with all generators running, or about 40 KW. This will vary with fuel pump configuration and use of galley and emergency loads like alternate flap drives.
Passenger galleys and entertainment loads will raise this significantly.