Evening all. At the risk of being ridiculed I wonder if someone can clarify something for me! On the initial inspection forms for installations there is a box for "maximum Demand". This can be in KVA or amps. I've been told that you add all the breakers on the board up then it is 40% of this total. I can't recall why its 40% and looking through all the books cannot ascertain why. I appreciate diversity and the like but in the books it can vary depending on the circuit, so why is it an overall 40% regardless of what's on the board? Any help appreciated. Domestic installation by the way.