An energy usage display unit for displaying energy usage of gas used for a water heater, water used for the water heater or electricity used in housing where the water heater is set. The energy usage display unit includes a clock section; a counting section for counting usage of gas, water or electricity; a memory section for storing a count value of usage counted by the counting section retroactive to past by a predetermined number with a predetermined time unit; a counting control section for writing the count value of usage at predetermined time; a display control section for reading one or both of the count value and a stored value in the memory section to prepare display data of usage; and a display section for displaying usage based on the display data prepared by the display control section.