Bob Minchin coughed up some electrons that declared:

I can't see the value for logging the data from Current Cost units apart
from the initial technical challenge. With so many domestic loads being
non resistive, and these units not taking a phase reference, they are
bound to be inaccurate. Yes they will give a relative indication to help
track down wasted power but that is about all they are good for. It
would be so easy to have a smarter clamp head that also plugged in to a
mains socket and have the pic calculate true RMS power.
Does anyone know of a unit that does this properly?

Bob

This is true - but don't most PSUs at least try to have a power factor of 1?

That leaves motors and old style tube lights.

I expect the problem was that many people don't have a 13A socket next to
the meter.

However, seeing as the base unit plugs in, if they used an unregulated AC
wallwart, perhaps with some extreme cleverness, they could achieve high
accuracy time synchronisation between the clamp unit and the base unit,
then the clamp could send a current sample set with timestamps and the base
could take a high resolution sample of the voltage profile.

It would be an interesting exercise...

Cheers

Tim