The problem I had was the PV inverter fed in to a consumer unit in my tractor shed which has got other circuits on it. This is then fed from my garage which has other circuits on it which then goes back to my main incoming consumer unit which has the house loads on it and of course the import meter. So yes in short it is an easy and relatively easy (theoretically anyway) idea to put CT's on all your incoming and outgoing circuits and simply sum them but in practical terms this wasn't possible for me. However if you can get away with multiple CT's then writing the code isn't difficult. I'll try and help if you tell me exactly what you want but I'm not very swift at this Arduino thing either so just post and one of the clever fellows will be along to sort you out.