noun
water heater; domestic boiler
Refers to a device that heats water for household use, such as bathing or kitchen taps. Often used in contexts like apartments, homes, and commercial facilities.
新しい給湯器を設置したので、お風呂がすぐに沸くようになった。
We installed a new water heater, so the bath heats up quickly now.
給湯器の調子が悪くて、
The water heater is acting up and there's no hot water.
Compound of 給湯 (kyūtō, 'hot water supply') + 器 (ki, 'device'). The term is straightforward and modern, with no obscure historical derivation.