Using components I already have, hopefully without the need to purchase anything else.

The first current transformer (CT) was from an Ega energy monitor 71A - 25mA.

No of coils = 71 / 0.025 = 2480

The second CT purchased from eBay a YHCD SCT013 100A 50mA cost £7.91

No of coils = 100 / 0.050 = 2000

Burden resistor calculation

CT1 = // PV - measured between inverter and consumer unit

CT2 = // measured at my side of supply grid's meter

Circuit is based in Robin Emerly's PV router mk2

Tests run using his code with scripts: rawSamples.ino phase Checker and calPhase

Calibration to follow.