Everyone keeps mentioning 'Diversity'. My mate mentioned it too. What has a street dance troupe got to do with my kitchen electrics….…..
Not a lot, but it has a meaning in relation to electrical items, particularly cooking appliances
If (as with cooking appliances) they are thermostatically controlled, it is very unusual for all the bits (oven elements, hob rings etc.) to all be drawing current simultaneously and continuously for long periods of time, since each of them 'cycles on and off', under the control of thermostats
As a result, the average amount of power consumer (i.e. average current) over an appreciable period of time (say 30 mins, probably less), which is what determines cable heating etc, will be appreciably less than the total if 'everything were drawing current simultaneously and continuously throughout that period.
The usual calculation for domestic cooking appliances says that the 'after diversity' current (effectively the average current over an appreciable period of time) is "the first 10 A plus 30% of the rest of the theoretical maximum current (with 'everything drawing current simultaneously).
Hence,for example, if the 'rating' of a cooking appliance (which is that 'maximum with everything on simultaneously') were, say, 30 A, then the 'after diversity' ('average') current, used for design purposes would be 10 A plus 30% of the other 20 A - i.e. just 16A
Hope that helps.