Okay, so i'm putting in a new circuit (single cable, not ring!) to the old WC at bottom of garden in order to power a ceramics kiln i have.
14M indoor cabling, 16m outdoor.
Kiln is 3.75 KW = 16.3A
So if i do a Voltage drop calc based on 2.5mm cable:
30M * 16.3A = 8.2V : Drop = 3.62%...