Heat Pump Sizing: Avoid the 3 Common Mistakes
4–6 minute read • Auckland homes
Mistake 1: Choosing by brand, not capacity
Capacity (kW) matters more than the logo. An undersized unit runs hard, costs more to run, and won’t keep up on cold nights. Oversized units short-cycle and can feel drafty.
Mistake 2: Ignoring room size and insulation
Use the quick guide below for Auckland’s mild climate. Adjust up if the room is very high, poorly insulated, south-facing, or very draughty.
| Room size (approx.) | Typical capacity | Notes |
|---|---|---|
| Up to 20 m² (small bedroom/office) | 2.0–2.5 kW | Quiet operation is key for bedrooms. |
| 20–30 m² (large bedroom/small lounge) | 2.8–3.5 kW | Great all-rounders for most spaces. |
| 30–40 m² (medium lounge) | 4.0–5.0 kW | Check ceiling height and insulation. |
| 40–60 m² (open-plan living) | 5.4–7.1 kW | Consider airflow and indoor unit placement. |
Mistake 3: Poor placement and airflow
- Mount on an internal wall with clear airflow along the room, not blasting straight at seating.
- Keep the outdoor unit clear of shrubs and away from bedrooms if possible.
- Clean indoor filters every 4–6 weeks during heavy use.
When to consider multi-split or ducted
Multiple rooms to heat/cool? A multi-split can run 2–5 indoor heads from one outdoor unit. For whole-home comfort and a discrete look, ducted systems are ideal — best assessed on site.
Quick tip: For bedrooms, quieter smaller units with good dehumidify modes feel more comfortable than oversizing.
Want a right-size recommendation?
We measure your rooms, check insulation and airflow paths, and recommend the most efficient capacity and placement for Auckland conditions.
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