Clear Signs That Reveal a Poorly Sized Wall-Mounted Heat Pump
At AirGreen, we understand how crucial the proper sizing of a wall-mounted heat pump is to ensure optimal comfort, energy savings, and maximum system lifespan. A unit that’s too small or too large for the space it’s supposed to heat or cool can lead to a host of problems that directly impact your daily comfort and electricity bill.
In this article, we highlight the concrete signs that indicate your wall-mounted heat pump might be undersized or oversized, based on real-life cases we’ve encountered in Montréal, Laval, Longueuil, on the North Shore and the South Shore. We also share practical advice and on-the-ground expertise to help you better understand the issues related to HVAC sizing.
Why Proper Sizing Matters
A properly sized wall-mounted heat pump allows you to:
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Maintain a stable and comfortable temperature year-round
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Reduce energy consumption
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Prevent premature wear and tear
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Ensure quiet operation
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Optimize eligibility for available grants (e.g., Hydro-Québec’s LogisVert Program)
On the other hand, a poorly sized unit can quickly become a real headache, both in terms of comfort and operating costs.
Signs Your Wall-Mounted Heat Pump is Undersized
1. Your system runs continuously without reaching the desired temperature
A heat pump that’s too small simply can’t keep up with the thermal demands of your space. It ends up running constantly, which increases electricity use and shortens the system’s life span.
Real example: In Longueuil, a customer chose a 9,000 BTU wall-mounted unit for a 1,200 sq. ft. home. The result: the heat pump ran nonstop and still couldn’t maintain a stable temperature in the winter. We replaced it with a Gree Lomo 18,000 BTU heat pump that was perfectly sized, and the issue was instantly resolved.
2. Certain areas of your home stay cold or hot even with the unit running
Uneven temperature distribution is a common symptom of an undersized unit. Some rooms just don’t get enough heating or cooling airflow.
3. A spike in your electricity bill with no clear explanation
A unit that runs all day trying to make up for its lack of capacity uses more energy, even if it’s rated as energy efficient.
Signs Your Wall-Mounted Heat Pump is Oversized
1. Your system turns on and off frequently (short cycling)
A unit that’s too powerful for the space quickly reaches the desired temperature, shuts off, and restarts shortly after. This behavior, known as “short cycling,” leads to premature compressor wear and increases the risk of breakdowns.
Real case: In Laval, a 700 sq. ft. condo was equipped with a 24,000 BTU wall-mounted heat pump. The result: constant short cycles, inconsistent comfort, and frequent noise. We recommended a Sharp ZU1 12,000 BTU, which was perfectly suited to the space. Comfort was instantly restored.
2. Thermal discomfort despite high power output
An overly powerful unit heats or cools the air too quickly, not giving it enough time to circulate evenly throughout the room. This creates hot or cold spots and an excess feeling of humidity or dryness.
3. Premature wear and more frequent maintenance
An oversized heat pump’s components are unnecessarily overworked. Filters need cleaning more often, noise levels increase, and breakdowns become more common — these are symptoms we regularly encounter in the field.
How to Avoid Sizing Mistakes
Custom Thermal Assessment
Before every installation, at AirGreen, we conduct a complete evaluation of your square footage, insulation, window orientation, number of occupants, and electronic appliances in the home.
Careful Selection of BTU Capacity
We only recommend models tailored to your actual needs: from the Fujitsu KZAH 9,000 BTU to Gree Extreme 24,000 BTU units, and even Bosch BIVA IDS Premium systems. Each unit is chosen to deliver the best energy performance and optimal comfort, without excess power.
Compliance With Grant Programs
A poorly sized heat pump can jeopardize your eligibility for grant programs like LogisVert. At AirGreen, we ensure your installation meets all technical criteria so you can receive up to $2,500 in financial assistance.
Our Practical Advice for Homeowners
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Don’t rely on BTU alone. Room layout, insulation, ceiling height, and natural ventilation all play a big role.
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Avoid generic advice found online. Every home is unique.
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Trust a certified installer who knows the Montréal, Laval, Longueuil, North Shore and South Shore markets.
Client Testimonial: Successful Intervention in Sainte-Julie
A couple contacted us after having a 18,000 BTU wall-mounted heat pump installed by another company in their 850 sq. ft. bungalow. They quickly noticed excess humidity, thermal discomfort, and frequent start-stop noises.
Our assessment revealed the unit was oversized. We removed it and installed a Gree Lomo 12,000 BTU wall-mounted heat pump, while recalibrating airflow. The result: restored comfort, a 30% drop in their electricity bill, and instant eligibility for the LogisVert grant.
In Conclusion: Rely on HVAC Sizing Experts
At AirGreen, we know that every detail counts when choosing the right wall-mounted heat pump. A poor assessment can harm your comfort, your budget, and your system’s lifespan. Our experts provide a tailored analysis, top-performing products, and installations that meet the highest HVAC standards.
Montréal, Laval, Longueuil, North Shore or South Shore — we are your go-to experts for a perfectly sized heat pump installation.