Installing a wall-mounted heat pump in Montréal is an excellent decision to improve the comfort of your home while reducing your energy bill. However, despite the many advantages of these systems, several common mistakes can seriously compromise their performance, lifespan, and your return on investment. At AirGreen, backed by our expertise in wall-mounted heat pump installation in Montréal, Laval, Longueuil, on the North Shore and South Shore, we’ve encountered many real-life situations where simple errors led to major additional costs for our clients.
In this article, we share the 7 most costly beginner mistakes we frequently see, illustrated with real-life anecdotes from our installation projects. Our goal: to help you avoid these pitfalls and guide you toward an optimal HVAC installation.
Incorrect heat pump sizing: the number one trap
The most common—and potentially most expensive—mistake is choosing a wall-mounted heat pump with a BTU capacity that doesn’t match the real needs of your space.
Real-life example: oversizing in Rosemont
A client in Rosemont contacted us after having a 24,000 BTU unit installed in a 900 sq. ft. condo. The result: short cycling, excessive energy use, discomfort, and lingering humidity. We had to uninstall the system and replace it with a 12,000 BTU Gree Lomo model, more appropriate for the space. A simple initial mistake that cost more than $1,800 in additional fees.
Our advice:
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Always have a heat load calculation done by professionals like us.
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Don’t guess: square footage alone isn’t enough to determine the right capacity.
Installing it in the wrong place: a choice that can cut efficiency in half
The indoor and outdoor positioning of the heat pump is crucial for its efficiency and longevity.
Installation mistake in Ahuntsic
In a project in Ahuntsic, the client insisted on placing the outdoor unit on a narrow, semi-enclosed balcony, thinking it would be better protected from the cold. But the airflow was blocked, which caused frequent defrosting errors. We had to relocate the unit at our expense to ensure proper performance.
Our advice:
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The indoor unit should be installed away from obstacles and positioned to cover the largest area.
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The outdoor unit should be sheltered from prevailing winds, but never in a confined space.
Neglecting home insulation: a costly long-term mistake
Even the best wall-mounted heat pump can’t make up for poor insulation. Yet many clients overlook this crucial factor.
Project in Longueuil: major energy loss
A homeowner in Longueuil contacted us for the installation of an 18,000 BTU Fujitsu KZAH heat pump. During our assessment, we found poor insulation in the attic and windows. Rather than masking the issue by upsizing the unit, we guided the client to an energy retrofit program, which helped reduce their annual consumption by 35%.
Choosing a model without checking available rebates
Several clients purchase a system without realizing they could have qualified for substantial rebates by choosing a slightly different model.
Typical case in Laval
A client had a Toshiba model installed that wasn’t eligible for the Hydro-Québec LogisVert program. If they had gone with an 18,000 BTU Gree Extreme heat pump, they would’ve received a $1,704 rebate. Too late. At AirGreen, we always consider these factors up front to maximize your savings.
Hiring an uncertified contractor
It may seem obvious, but many clients are tempted by “cheaper” installers. The lower initial cost can quickly turn into a financial nightmare.
Non-compliant installation in Saint-Léonard
We were recently called in for an emergency in Saint-Léonard, where a 24,000 BTU Haxxair heat pump had been installed without following B52 code. Risk of refrigerant leaks, no backflow valve, incorrect wall bracket… The system had to be completely reinstalled.
Our advice:
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Make sure to hire an RBQ-certified contractor, with licensed refrigeration technicians.
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Ask for local references — at AirGreen, we provide a full project history.
Skipping annual maintenance: a silent but expensive mistake
A poorly maintained wall-mounted heat pump can lose up to 25% of its efficiency in just 2 years. Maintenance isn’t optional — it’s essential.
Example in Brossard
A client in Brossard called us about performance issues with an 18,000 BTU Zephyr model installed three years earlier. The filter had never been cleaned, the outdoor unit was clogged with leaves, and the coils were dirty. A full maintenance visit solved the issue, but it could have been prevented.
Ignoring Montréal’s harsh winters
Not all wall-mounted heat pumps are designed for the cold winter conditions of the region. Installing the wrong model can lead to breakdowns in the middle of February.
Example in Blainville
A client had chosen a generic Chinese model (not NEEP certified) purchased online. The result: frequent shutdowns below -15°C. We replaced it with a 12,000 BTU Bosch BIVA-R, specially designed to maintain its performance down to -30°C.
Conclusion: AirGreen’s expertise, your best ally against costly mistakes
At AirGreen, we don’t just sell products. We offer custom HVAC solutions, tailored to your situation, comfort goals, and budget. Thanks to our field experience across Montréal, Laval, Longueuil, and both the North Shore and South Shore, we know how to spot issues before they become expensive problems.
If you’re thinking about installing a wall-mounted heat pump, make sure to do it with the right partners, the right methods, and the right information.