Abstract: An adapter to be plugged in between a conventional watt-hour meter and an electrical power use installation socket to protect both the meter and downstream equipment from possible damage by transient surges in electrical potential resulting from lightning or similar disturbance. For the usual meter having a pair of power input terminals and a pair of power output terminals, this adapter has a pair of varistors or similar non-linear resistances connected between the respective input terminals and ground, so as to conduct away such surges. It also preferably has a heat sink connected to the grounded side of the varistors to dissipate the thermal energy resulting from the surge conduction. Additional features include an indicator of operating condition and fuse links to the varistors.