A combi boiler, short for combination boiler, is a type of boiler that provides both space heating and domestic hot water in one compact unit. Unlike conventional boilers, which require a separate hot water tank, combi boilers heat water directly from the mains on demand, which makes them highly energy-efficient and financially efficient. They are also space-saving, as they require little space in your home. Combi boilers use condensing technology to efficiently heat the system water by extracting latent heat from the flue gases. During the heating season, the combi boiler runs as needed to heat a structure and provide hot water for showers, sinks, and other hot water appliances. During the summer months, the combi boiler only fires when there is a call for domestic hot water. Combi boilers are popular with apartment and condominium owners, and homeowners in regions where homes do not have basements, due to their small size and space-saving design.