It is an object of the invention to provide a radio remote controller system that, when power saving for a radio remote controller is realized by intermittently setting a data receivable period in the radio remote controller, can easily and flexibly change a length of a period for making it impossible to receive the radio data and reduce power consumption of the radio remote controller. A master set connected to a water heater main body by wire transmits monitor data G(G.sub.1, G.sub.2, G.sub.3) indicating an operation state of the water heater main body, which include transmission time information indicating the next time (t.sub.14 at G.sub.1, and t.sub.17 at G.sub.2) of transmission of the monitor data G, to a slave set serving as a radio remote controller. The slave set, which has received the monitor data G, comes into a "standby state" (slave set Rx and slave set Tx are OFF), in which power consumption is smaller than "data receivable state" (a slave set Rx is ON) and transmission and reception of radio data are impossible, until the next time of transmission of the monitor data G acquired from the monitor data (T.sub.off1, T.sub.off2, T.sub.off3). When start time (t.sub.13, t.sub.16) for reception of monitor data has come, the slave set is switched from the "standby state" to the "data receivable state" to receive the monitor data G.