[jacquesm]

> I was thinking about hacking up a clip-on ammeter

The easiest spot is right on the distribution wires, they usually are pretty beefy and that means you don't have to re-hang your meter after every breaker. They're also very well insulated so the chances of shorting something out diminish a lot (but if you do the effects will be far more spectacular ;) ).

In the end I installed a 'Shelly' three phase current meter permanently with the pickups around the mains wires. That gave me very precise logging (and given that the distribution board passes those three wires roughly balanced out across the breakers it is already quite fine grained). It also allows you to spot intermittent consumers and for the money I wished I had installed it earlier during my hunt.