Abstract: An electric fence energizer is operated by an alternating current and has two storage capacitors (C.sub.1, C.sub.2), which are charged by a charging circuit (7) to a high voltage. The storage capacitors (C.sub.1, C.sub.2) are discharged through separate primary windings (L.sub.1, L.sub.2) in a transformer (T) and the secondary winding (L.sub.3) of the transformer is connected to the electric fence. The discharging processes are controlled by separate discharging circuits (R.sub.1, T.sub.y1 ; T.sub.y3 and T.sub.y3 respectively), so that for light loads only one of the storage capacitors (C.sub.1) is discharged, and for heavy loads also the other one (C.sub.2) is discharged starting a short time after the start of the discharging of the first one and during the same discharge cycle. Sense circuits (L.sub.2, R.sub.8, R.sub.9, C.sub.3, R.sub.10, R.sub.11, R.sub.12, T.sub.4, R.sub.13) provide signals PCHL; PPUL) to a microprocessor (7) and they represent the load on the transformer (T).