The influence of nanostructures concentration, morphology, permittivity and size on the augmentation of the dielectric breakdown characteristics of nano insulating oils has been experimentally examined and demonstrated in detailed for the first time. Various dielectric nanoparticles/structures, viz. zinc oxide (ZnO), zirconium oxide (ZrO2) and aluminium oxide (Al2O3), of different sizes over a range of 25–125 nm have been employed to investigate the influence of nanoparticles concentration as well as size on the dielectric performance of nano insulating oils. Bismuth oxide (Bi2O3), magnesium oxide (MgO) and copper oxide (CuO) have been utilized to investigate the effect of nanoparticles concentration and all the nanoparticles contribute to the detailed study on the effects of morphology on the breakdown characteristics. Experimental findings reveal that particle size, permittivity as well as concentration affects the dielectric performance of nano insulating oils to large extents. Particles with smaller size offer higher enhancements in the dielectric breakdown voltage compared to the bigger size particles and its mechanism and role in hampering streamer development and growth has been deliberated. The influence of temperature and moisture content has been found to have major effects on the BD performance and experimentally examined and reported. The present work reveals the potential of nanomaterials towards designing more robust power systems employing liquid dielectrics by engineering their breakdown characteristics. © 2016 Elsevier B.V.