The paper deals with thermochromic VO2 prepared by reactive high-power impulse magnetron sputtering and characterized by spectroscopic ellipsometry. We focus on the dispersion of optical constants in a wide temperature range and on the transmittance predicted using the optical constants. While the thermochromic behavior of VO2 in itself has been reported previously (particularly above the room temperature, RT), in this paper we present (i) optical properties achieved at a low deposition temperature of 250 degrees C and without any substrate bias voltage (which dramatically increases the application potential of the coating) and (ii) changes of these properties not only above but also below RT (down to -30 degrees C). The properties include very low (for VO2) extinction coefficient at RT (0.10 at 550 nm), low transition temperature of around or even below 50 degrees C (compared to the frequently cited 68 degrees C) and high modulation of the predicted infrared transmittance (e.g. 39% at -30 degrees C, 30% at RT and 3.4% above the transition temperature at 2000 nm for a 100 nm thick coating on glass). The results are important for the design of thermochromic coatings, and pathways for their preparation under industry-friendly conditions, for various technological applications. (C) 2016 Elsevier B.V. All rights reserved.