Find the right kW rating for your heat pump or split system. Enter your room size, insulation, and location for NZ and Australian climate zones.
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Select your country, climate zone, and room details. Results include heating load, cooling load, and estimated running cost.
Approximate kW ratings by room size for a well-insulated NZ home.
| Room size | Auckland / Waikato | Wellington / Christchurch |
|---|---|---|
| Small bedroom (10–15 m²) | 1.5–2.0 kW | 2.0–2.5 kW |
| Standard bedroom (15–20 m²) | 2.0–2.5 kW | 2.5–3.5 kW |
| Open plan living (25–40 m²) | 2.5–3.5 kW | 3.5–5.0 kW |
| Large open plan (40–60 m²) | 3.5–5.0 kW | 5.0–7.0 kW |
| Whole house (100+ m²) | 7.0–9.0 kW | 9.0–14.0 kW |
Assumes average insulation and ceiling height of 2.4 m. Use the calculator above for a more accurate result.
A 2.0–2.5 kW unit works for Auckland. In Wellington or Christchurch, go to 2.5–3.5 kW for colder winters. Always get an installer assessment for accurate sizing.
No. An oversized heat pump short-cycles — reaching temperature quickly without running long enough to dehumidify the air. Size accurately with a 10% buffer rather than going significantly oversize.
COP (Coefficient of Performance) measures efficiency. A COP of 4 means 4 kW of heat for 1 kW of electricity — 4× more efficient than a direct heater. Modern units have a COP of 3.5–5.0.
Run the calculator for each room separately, then sum the results to estimate total outdoor unit capacity. A licensed HVAC installer can design the right multi-head configuration.
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