The effect of annealing temperature on the electrochromic properties of acid-treated hydrated tungsten oxide (WO3 center dot H2O) nanoplates is reported for the first time. Nanoplates were grown on fluorine-doped tin oxide-coated glass substrate using nitric acid, and annealing temperature was varied from 100-400 degrees C. The as-prepared nanoplates were WO3 center dot H2O, and these nanoplates transformed into tungsten oxide (WO3) after annealing at >= 200 degrees C. Nanoplate thickness decreased with increasing annealing temperature from 12-55 nm for the as-prepared sample to 12-40 nm for the sample annealed at 400 degrees C. WO3 nanoplates annealed at 200 degrees C showed the best electrochromic properties with coloration efficiency of 28.64 cm(2) C-1, high optical modulation (58%), good electrochromic cycling stability, as well as short ion insertion and extraction times of similar to 9.6 and similar to 5.1 s, respectively. (C) 2015 Elsevier Ltd. All rights reserved.