This research deals with the preparation of silicone rubber (SiR), epoxy and EPDM based composite materials for outdoor high voltage insulationapplications. These composites were fabricated by incorporating nanosilica 2.5~5 % by weight, while the microsilica loading were varied from 10~20 % by weight. Uniform and homogenous dispersion of fillers were achieved through process parameters optimization. The tensile strength of fabricated polymer compositesincreases with the incorporation of filler contents. Even in case of hybrid composites, it increases up to 400 %. The prepared composite samples were found thermally more stable than their virgin counterparts. An approximate 25% increase in dielectric strength was also obtained. The novelty of the research work is promise of nano and hybrid composite towards their aging performance under multi-stress conditions. To comprehend the aging phenomena (weathering characteristics) under multi-stress conditions, the entirepolymer composites were aged for a maximum of 5,000 hrs in a multi-stress aging chamber developed as per IEEE standard 1109. Different stresses like ultraviolet, thermal, salt-fog, acid rain and voltage were applied for specifically designed weather cycles. After multi-stress aging according to the data of hydrophobicity loss silicone rubber composites were placed in HC-3 while epoxy and EPDM composites were grouped in HC-4 and HC-5 respectively. The results of leakage current during the multi-stress aging for silicone rubber, epoxy and EPDM composites were found 0.8μA, 1μA and 1.2μA correspondingly. The hybrid polymer composites due to synergic effects responded better towards aging. Percentage deterioration of fabricated compositesalso demonstrated that hybrid composites performed better thannano and micro composites respectively.