7 Costly Heat Pump Installer Mistakes to Avoid

A well-specified heat pump installed badly will underperform for its entire 20-25 year life. Based on feedback from homeowners in our network, here are the seven most common installation mistakes and what to look out for.

Mistake 1: No heat loss survey. Any installer who provides a quote without carrying out a formal heat loss survey (BS EN 12831) is guessing at the system size. An undersized unit will struggle in cold weather; an oversized unit short-cycles. The survey is mandatory for BUS grant claims and should be standard practice regardless.

Mistake 2: Old radiators left unchanged. Heat pumps run at lower flow temperatures than gas boilers. Radiators sized for a 70°C boiler will not deliver adequate heat at 45°C. A proper installer will calculate whether existing radiators are adequate at the new flow temperature and recommend upgrades where needed.

Mistake 3: Incorrect refrigerant charge. Heat pump refrigerant must be charged to precise specifications. Under or overcharging affects efficiency and can void the manufacturer warranty. This requires specialist equipment and training - confirm your installer is F-Gas certified.

Mistake 4: Poor siting of the outdoor unit. The outdoor unit needs adequate airflow clearance - typically 300mm minimum on all sides. Positioning it in a corner, behind a fence, or directly against a wall restricts airflow and reduces efficiency. North-facing installations in particularly cold spots can also reduce winter performance.

Mistake 5: Incorrect hot water cylinder sizing. Most heat pump installations require a dedicated hot water cylinder (unvented or vented). An undersized cylinder means you run out of hot water; an oversized one wastes energy heating water you don't use. The standard recommendation is 200-250 litres for a 3-4 bedroom home.

Mistake 6: Rushing commissioning. Commissioning - the process of setting flow temperatures, checking refrigerant pressures, calibrating controls - is where efficiency is fine-tuned. Rushed commissioning (a day where 3+ properties are being handed over) leads to suboptimal settings that are never corrected. Ask specifically who will commission your system and how long they allocate for it.

Mistake 7: No post-installation monitoring period. A good installer will check in after the first full heating season (or at least the first cold month) to review system performance data and adjust settings. Heat pump controls need tuning to your specific home's behaviour. If an installer disappears after handover, you lose this optimisation opportunity.