Recommended cylinder size
180L
Estimated daily hot water draw
136L
Recovery rate guidance
A 180L cylinder on a gas boiler usually recovers quickly, so once-daily heavy shower use is manageable with correct controls and coil performance.
Heat pump coil sizing note
Heat pump cylinders work best with larger coils and lower-temperature charging, so avoid undersizing if you expect back-to-back showers.
| Cylinder size | Suitability | Typical fit |
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Methodology
How the cylinder size is estimated
The tool estimates usable daily hot water demand from household size, bathrooms, showers, baths, and whether dishwashing hot water is likely to come from the cylinder. Showers dominate daily demand in most homes, while baths add a large but less frequent weekly allowance.
That estimated draw is then converted into a practical cylinder recommendation, with extra margin where there are more bathrooms, higher concurrency risk, or a slower-recovery heat source. Heat pumps and immersion-only systems usually benefit from more stored volume than a fast-recovery gas boiler.
Suitability ratings for 150L, 180L, 210L, 250L, and 300L cylinders are generated by comparing each size with the estimated daily demand and expected recovery profile. Solar thermal and solar-diverter setups may justify nudging cylinder volume upward to increase useful stored solar energy.
This is a planning guide only. Final cylinder selection should also consider cupboard space, coil output, legionella control strategy, recovery time, hot water temperature assumptions, and whether multiple simultaneous showers or high-flow baths are likely in real use.
Related guides
Heat Pump Installation Cost
Understand when a cylinder becomes part of a full low-carbon heating project.
What Size Heat Pump Do I Need?
Coordinate cylinder size with occupancy, emitters, and overall heating design.
Boiler Replacement Options
See when hot water storage changes your replacement pathway.