That would be 2.5 for power, but not all electricians run this, some I've seen have run the slightly cheaper 1.5 for power. Not all houses have circuit breakers, and those that use fuses can usually be upgraded to breakers from pretty much any hardware store etc. Such add-in breakers come in 8A, 16A, 20A and 32A, all the same physical size. There is nothing stopping someone from plugging in a 32A breaker on their lights because they've got a few hundred downlights installed. Yes, I think this is the case, but I'd sure like to be able to pull through just a few more amps. My power is underground so running 3-phase isn't really a viable option, not when the conduit needs to be dug up and then replaced.