In this experimental work, three types of water-based nanofluids are prepared by ultrasonic method. SiO2, TiO2 and CNT nanoparticles are used for preparing the nanofluids. Applications of these nanofluids are examined in the heating process in HVAC systems. During the experiments, total dissolved solids (TDS) of nanofluid are measured to see which nanofluid is more appropriate in heating process and makes the lower deposits and sediments. Also, heated area and nanofluid temperatures are recorded to show which nanofluid in suitable for heating from energy consumption view point. Results show that SiO2 can be more suitable from the energy consumption view point because by lower energy consumptions, it reaches to desirable temperature in the heated area. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.