The morphology-controlled synthesis and near-infrared (NIR) absorption properties of W18O49 were systematically investigated for the application of innovative energy-saving windows. Various morphologies of W18O49, such as nanorods, nanofibers, nanograins, nanoassembles, nanoplates, and nanoparticles, with various sizes were successfully synthesized by solvothermal reactions using organic alcohols as reaction media and WCl6, W(EtO)(6), and WO3 solids as the tungsten source. W18O49 nanorods of less than 50 nm in length showed the best optical performance as an effective solar filter, which realized high transmittance in the visible region as well as excellent shielding properties of NIR light. Meanwhile, the W18O49 nanorods also exhibited strong absorption of NIR light and instantaneous conversion of the absorbed photoenergy to the local heat.