Thanks Phil and Bob.
Yes that did occur to me after posting. I fitted a small CU to the garage at my old house so should have remembered.
Funnily enough I think there is already a small hole in the top right of my main (first) CU. It’s the slightly older plastic one (current regs say that they have to be metal I think). That hole looks large enough to feed the cables out of.
My only issue now is that I have 3 consumer units. Bob, the CU is basically just din-rail mounted circuit breakers and RCDs in a plastic enclosure.
I have 3 of them though which leaves me in a predicament with what device to use. I want the large number of inputs of the Iotawatt for the main CU, which has approx. 7 circuits coming off it, plus the main feed in off the 100A fuse, but then there is another CU in the utility room that has another 7 or so circuits coming off it. Then there’s a small one in the garage, which I would like to monitor because that runs off to some stables and various bits of outdoor or shed lighting that might accidentally get left on.
It seems like my scenario is an ideal one for that other UK-made product, with the separate TX and Base etc, but they have too few inputs on them.
I suppose I could start with just 2x iotawatts in the house, feeding their stats to emoncms running on one of these mini-PCs I have sat in the drawer (Intel NUC, Gigabyte BRIX). The feed to the garage could just be monitored in-full rather than per-circuit in the garage. It should be at zero most of the time… so that would be a good enough indication.