The standard sizing guide for Christchurch hot water cylinders is 45–55 litres per person. A couple needs a 135L cylinder; a family of four needs 180–200L; a family of five or more needs 250–300L. Always round up if your household has long showers or high hot water demand.
| Household Size | Recommended Cylinder |
|---|---|
| 1–2 people | 135L |
| 3–4 people | 180–200L |
| 5–6 people | 250–300L |
| High demand / large family | 300L+ |
Yes — a larger cylinder holds more hot water and costs more to heat initially, but it also means fewer reheating cycles if demand is high. An undersized cylinder that constantly reheats from cold is less efficient than a correctly sized one. Sizing up by one size when in doubt is usually the right call.
Heat pump hot water cylinders are typically supplied in 180L, 250L, and 300L sizes. The compressor heating rate is slower than an electric element, so slightly larger sizing is recommended — a heat pump 250L suits a family of 3–5 rather than 3–4 for a standard electric.