A gas boiler is a heating system that uses natural gas or propane to heat water, which is then circulated through a network of pipes to provide warmth to a building. Gas boilers are commonly used for residential and commercial heating purposes, including space heating and providing hot water for domestic use.Gas boilers are known for their efficiency and reliability. Modern condensing gas boilers are highly efficient, capturing and using more of the heat generated during combustion, which leads to energy savings and reduced environmental impact.