The exemption is available only provided the amount of gas or heat supplied by the operator to the network is no more than 20% of its turnover amount.
Mae’r esemptiad ar gael dim ond ar yr amod nad yw swm y nwy neu’r gwres a gyflenwir i’r rhwydwaith gan y gweithredwr yn fwy nag 20% o swm ei drosiant.