Polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) composite polymer electrolyte loaded with 3-isocyanatopropyltriethoxysilane (IPTES) functionalized zirconium oxide (ZrO2) nanoparticles is successfully synthesized and evaluated for electrochromic application. Incorporation of ZrO2 into the polymeric substrate enhances the ionic conductivity of the electrolyte. Meanwhile, the functionalization of ZrO2 nanoparticles with IPTES ligand enhances the electrolyte's optical transmissivity. The amount of ligand and its time of reaction with ZrO2 are found to affect the overall property of the electrolyte. The electrolyte exhibits a balance of low crystallinity and low ZrO2 aggregation and agglomeration resulting to a potential next generation electrolyte for energy efficient windows. (C) 2016 Elsevier Ltd. All rights reserved.