A heat only boiler (also known as an open vent boiler) generates thermal energy in the form of hot water. A heat only boiler provides both central heating and hot water for use in heating applications. Unlike combined heat and power boilers which use heat from electricity generation, heat-only boilers are dedicated to just generating heat.

Hot water is pumped from the system boiler through the heating system to the radiators and hot water cylinder, resulting in more economical running costs. Heat only boilers mean that more than one tap can be used at a time; the boilers require more space and are suited to larger homes.
A heat boiler station can use different fuels, such as natural gas, heating oil, woodchips and straw.