Storage systems: volume plus recovery
A storage system holds a set volume of heated water and reheats it at a set rate. If your household empties the tank every morning, recovery rate matters as much as volume. Gas storage generally recovers faster than electric; heat pumps recover more slowly again.
Continuous flow: litres per minute
A continuous flow unit is rated in litres per minute at a given temperature rise. A typical shower draws roughly 8 to 10 litres per minute. Two showers at once therefore need a unit rated well above a single-shower figure, and a kitchen tap running at the same time adds to that.
| Simultaneous use | Approximate demand | Implication |
|---|---|---|
| One shower | 8–10 L/min | Entry-level flow rate is usually adequate |
| Shower + kitchen tap | 12–16 L/min | Mid-range unit |
| Two showers | 16–20 L/min | High flow-rate unit, and adequate gas supply |
Factors that push sizing upward
- Teenagers, or shift workers showering at different times
- A bath used regularly
- Multiple ensuites in use at the same time
- Long pipe runs that waste hot water before it reaches the outlet
- A spa bath or outdoor shower
Oversizing costs money to buy and to run. Undersizing produces cold showers. The point of an on-site assessment is landing between the two.