It recently occurred to me, after my neighbor bought a Toyota Rav 4 Prime plug-in hybrid (PHEV), to research certain differences (mainly in efficiency and performance) between it and my Kia Sorento PHEV. This has led me to a somewhat surprising supposition: I think the larger and heavier Sorento PHEV is a little more efficient, on battery power, than the Rav 4 Prime (note: the Toyota gets 4 mpg better, combined, on gas).