Combination boiler
Combination boilers, or ‘combi boilers’, supply central heating and hot water directly from the water supply, without the need for a water tank or hot water cylinder.
Because hot water is supplied ‘instantaneously’ rather than being stored and then used, they can provide unlimited hot water on demand, and are useful where there is limited space availability. This can be a more efficient type of boiler, as the hot water is used immediately, rather than being stored.
However, as there is no reservoir of hot water, when there are multiple simultaneous uses, the pressure may drop. This may make them best suited to smaller, lower-occupancy properties.
The English Housing Survey, Headline Report, 2020-21, published by the Department for Levelling Up, Housing and Communities in 2021, defines a combination boiler as a boiler that: ‘provides hot water or warm air for space heating and can provide hot water on demand negating the need for a storage cylinder, therefore requiring less space.’
[edit] Related articles on Designing Buildings
Featured articles and news
ECA, JIB and JTL back Fabian Society call to invest in skills for a stronger built environment workforce.
Women's Contributions to the Built Environment.
Calls for the delayed Circular Economy Strategy
Over 50 leading businesses, trade associations and professional bodies, including CIAT, and UKGBC sign open letter.
The future workforce: culture change and skill
Under the spotlight at UK Construction Week London.
A landmark moment for postmodern heritage.
A safe energy transition – ECA launches a new Charter
Practical policy actions to speed up low carbon adoption while maintaining installation safety and competency.
Frank Duffy: Researcher and Practitioner
Reflections on achievements and relevance to the wider research and practice communities.
The 2026 Compliance Landscape: Fire doors
Why 'Business as Usual' is a Liability.
Cutting construction carbon footprint by caring for soil
Is construction neglecting one of the planet’s most powerful carbon stores and one of our greatest natural climate allies.
ARCHITECTURE: How's it progressing?
Archiblogger posing questions of a historical and contextual nature.
The roofscape of Hampstead Garden Suburb
Residents, architects and roofers need to understand detailing.
Homes, landlords. tenants and the new housing standards
What will it all mean?
The Architectural Technology podcast: Where it's AT
Catch-up on the latest episodes.
Edmundson Apprentice of the Year award 2026
Entries now open for this Electrical Contractors' Association award.
Traditional blue-grey slate from one of the oldest and largest UK slate quarries down in Cornwall.
There are plenty of sources with the potential to be redeveloped.
Change of use legislation breaths new life into buildings
A run down on Class MA of the General Permitted Development Order.
Solar generation in the historic environment
Success requires understanding each site in detail.