With increasing attention on hydrogen (H-2) produced by renewable energy methods for transport and other applications, an updated evaluation of H-2 monitoring techniques is timely. The emergence of nanomaterials with unique properties enables a new class of H-2 sensing materials, exhibiting important attributes such as high surface area to volume ratio, reactivity and number of active sites. The development of these materials allows for improved H-2 sensing methods with increased sensitivity, selectivity, speed and improved economy for both financial cost and power consumption. These advances enable small-scale, high-performance H-2 sensors for use in emerging hybrid renewable energy systems, including Internet of Things (IoT) or mobile systems. While literature reports on H-2 sensors include thermal conductivity, resistive, optical, acoustic, electrochemical and catalytic methods, this review will focus on resistive H-2 sensing nanomaterials. Three classes of these nanomaterials are discussed: metal oxides, transition metal dichalcogenides, and graphene based nanomaterials. As a key aim of this review is improved economy of use, we will elaborate only sensors operating at temperatures lower than 200 degrees C, with a focus on potential for room temperature operation. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.