High voltage metal oxide surge arresters (MOSA) are stressed by overvoltages generated in a power system. The selection of standard methods for the energy absorption capability of high voltage MOSA is based on the discharge energy estimation. This paper discusses the energy stresses of metal oxide surge arrester due to shielding failure. The energy stresses are calculated for arresters located inside 220/66/11 kV Wadi-Hoff gas insulated substation in the Egyptian network. A lightning stroke with different magnitudes is applied at different points along the line connected between Wadi-Hoff substation and Tebbin-power stations and the energy stress in each case is discussed. The effects of incoming and outgoing feeders types on FTO magnitudes and energy stresses are presented and discussed.