South-Direct414 t1_j6fbebg wrote
Reply to comment by wiffleplop in Hot water tank malfunctioning by 18418871
I'd say as far as total energy consumption it's probably more efficient to separate the systems. That way you don't need to make your radiator out of human consumption rated materials, and you can also use more efficient heat transfer medium.
celaconacr t1_j6fkknz wrote
I'm pretty sure condenser boilers are more efficient (94% for a new one). The radiators are on a separate loop not combined with the hot water system so you don't need human consumption rating.
Most modern houses in the UK use a "combi" boiler. That's a radiator loop heater and tankless hot water system in one. It heats the cold water feed direct for hot water on demand but that does mean a supply limit. Advantages are no efficiency loss through hot water storage, no space loss for the water tank, no legionnaires or similar concerns.
The other common type is a tanked system. Again the boiler does all the heating but in this case either feeding a hot water tank or the radiators. Hot water tanks are more common in older properties, those with pressure issues or those with too high demand for a direct feed.
We will probably be going back to tanks as we are slowly moving towards heat pumps from gas boilers.
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