7 Common Heat Pump Installation Mistakes and How to Avoid Them

Heat pumps are an excellent low-carbon heating solution, but their performance depends heavily on proper installation and design. In this guide, we walk through the most common heat pump installation mistakes made in UK homes — and how to ensure your system runs efficiently from day one.

1. Incorrect Sizing: Too Big or Too Small

Why it matters:A heat pump must match the building’s heating needs. This is determined by calculating heat loss, which includes both:

• Fabric losses: Heat escaping through walls, windows, roofs

• Ventilation losses: Draughts, open chimneys, and general air leakage

If the heat pump is undersized, it won’t be able to heat your home properly. If it’s oversized, it may short-cycle (constantly turning on and off), which reduces efficiency and wears out the compressor prematurely.

Pro tip:Correct sizing is based on detailed heat loss calculations, not just floor area. If you plan to extend or change your heating needs in the future, allow some sizing flexibility.

2. Poor Communication Between Installer and Homeowner

Why it matters:Many installation issues arise from a lack of clear discussion between the installer and homeowner. Your comfort expectations — such as preferring a warmer home — must be communicated upfront, especially for elderly or sedentary households.

Pro tip:Ask your installer about design temperatures. A system designed for 21°C won’t keep your home at 23°C unless it’s sized accordingly.

3. Wrong Refrigerant Charge (Rare, But Possible)

Why it matters:Too much or too little refrigerant in a heat pump can impact efficiency and damage the system. Fortunately, most domestic heat pumps in the UK are monobloc units, which are factory-sealed and pre-charged.

Pro tip:Unless your system is split or has developed a refrigerant leak, incorrect charging is unlikely. Always choose an installer certified to handle refrigerant if repairs are needed.

4. Poor Location of the Outdoor Unit

Why it matters:Heat pumps need free-flowing air. Air enters the unit at the back and exits as colder air at the front. If the cold exhaust air is blocked or recycled into the intake, efficiency plummets.

Mistake to avoid:Placing the unit near a wall, in a narrow alley, or enclosing it in an unventilated box can cause poor airflow.

Pro tip:Ensure there's clear space behind and in front of the unit. Specialist covers are available that protect appearance without impeding airflow.

5. Wrong Ground Conditions for Ground Source Heat Pumps

Why it matters:Horizontal ground loops need moist, thermally conductive soil. Installing them in dry or poorly conducting soil (like chalk) can drastically reduce performance.

Solution:Get a detailed thermal geology survey before installing a ground source system. Vertical boreholes or deeper collectors may be better suited if space or soil conditions are poor.

Pro tip:Installers should consult with qualified hydrogeological designers for accurate assessments of soil conductivity and seasonal heat recovery.

6. Thermostat Placement in the Wrong Location

Why it matters:Installing a thermostat in a sunny spot, near a radiator, or in a draughty area can give inaccurate readings, leading to uneven heating.

Pro tip:Place the thermostat in a central, shaded area away from direct heat for more reliable control. This is a general HVAC rule, but especially important for heat pump efficiency.

7. Underestimating the Planning and Design Required

Why it matters:Gas boilers are forgiving. You can install them poorly and still get heat. Heat pumps are less tolerant of design errors, especially when it comes to:

• Radiator sizing and flow temperatures

• Hot water cylinder capacity

• Controls and zoning

Pro tip:Choose an installer who takes time to design the full system properly — not just fit the unit.

Bonus Tip: Use Trusted Resources to Choose the Right Installer

The most important decision you’ll make is choosing the right installer. Look for those who:

• Conduct full heat loss surveys

• Can explain flow temperatures and system volumes

• Provide personal references or access to real-life installations

Use resources like Nesta’s “Visit a Heat Pump” directory to find homes near you with installed systems. You can contact homeowners directly to learn from their experience.

Summary Table: Key Heat Pump Installation Mistakes

Final Thoughts

Installing a heat pump is a long-term investment in energy efficiency and comfort. But to get the best results, you need more than just the right technology — you need the right planning, the right installer, and the right design decisions.

Avoiding these common heat pump mistakes will ensure you get the comfort, savings, and sustainability benefits you’re aiming for.