Thanks. Sounds like I need to do some investigation of the Energy Monitor unit to figure out the RS232 bit. There is an active group pvbeancounter that I might investigate on that subject.
One question - what is a RS232 'shield' that I see mentioned? Is this the sort of interface component I could use?
Here in the state of New South Wales in Australia we are on 'net' metering for the solar, and 'time of day', aka smart metering, for our consumption. Any extra that we generate goes back to the grid and we get paid a miserly amount for it. In winter our house tends to be cold so I was particularly interested in having a control system that would auto cut in a small fan heater whenever we had sufficient surplus capacity. Then cut it out again when say a cloud came over, or the freezer or fridge cut in etc.