John wrote:

you need a digital data logger connected to a PC. eg Maplin sell
multimeters with RS232 output which give a serial data o/p. so if the load
has no phase problems you just need to measure the current. I don't have
detailed knowledge of the specs.


If I'm going to go down the data logger route, I will probably go for
one of these:
http://www.audon.co.uk/labjack.html

I used one before in a previous project, and found it to be a very nice
piece of kit.

But that wasn't my question really - I can see how to get the
measurement I want by sampling V and I with a data logger - but I can't
help wondering if there isn't a cleverer, simpler way, given that all I
want is total energy.

Another way of asking the question - I can see how to integrate the data
electronically, after collecting a huge number of data points. But I'm
wondering if there isn't another way of doing the integration. If that
makes sense.


--
Grunff