In this paper, an analytical expression for characteristic equation of a partially covered photovoltaic thermal compound parabolic concentrator (PVT-CPC) water collector system similar to Hottel-Whillier-Bliss (HWB) equation of flat plate collector has been derived. The derivation is based on basic energy balance equation for each component of partially covered PVT-CPC water collector system. The analytical result of proposed partially covered PVT-CPC water collectors [case (i)] has been compared with [case (ii)]: fully covered PVT-CPC water collectors; [case (iii)]: conventional CPC water collectors and [case (iv)]: partially covered PVT water collectors. It is observed that (a) an overall exergy efficiency of partially covered PVT-CPC water collector (25%PV) system is maximum and (b) an instantaneous thermal efficiency of conventional CPC water collector system [case (iii)] is maximum as compared to other cases. (C) 2014 Elsevier Ltd. All rights reserved.