Choosing the Wrong Size for a Central Heat Pump Can Be Extremely Costly
In the world of residential HVAC, a heat pump sizing mistake can quickly turn into a financial nightmare. That’s exactly what happened to a homeowner in the North Shore of Montréal, who had to replace their entire system… out of pocket. At AirGreen, we were called in to fix the situation — a delicate mission, but one full of key lessons to prevent this type of mistake from happening again.
The Backstory: An Undersized Initial Installation
When this client hired an independent contractor to install a central heat pump, the heat load calculation was rushed, with no real consideration of insulation, number of floors, or window coverage. The result:
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A 24,000 BTU (2-ton) unit installed in a 2,400 sq. ft. two-storey home
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Cold rooms in winter and overheated spaces in summer
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Premature compressor wear due to continuous operation
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A spike in energy bills
Six months after installation, the system failed. Not covered under warranty (the installer wasn’t certified), the client paid $4,200 to remove and replace the unit with a properly sized model.
How to Avoid This Mistake? The Critical Role of Proper Sizing
Proper central heat pump sizing depends on several key factors, all of which we systematically analyze at AirGreen:
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Actual living space (including the basement if heated)
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Sun exposure and size of windows
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Level of insulation (walls, roof, windows)
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Number of occupants and room usage
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Complementary equipment (baseboards, fireplace, ventilation)
Our Solution: A Compliant, High-Performance, Long-Lasting Installation
After taking over the project, our team conducted a full heat load assessment. We recommended and installed a Goodman GSZC18 3-ton (36,000 BTU) central heat pump, equipped with a two-stage Inverter compressor and R-32 refrigerant, which is more eco-friendly.
Technical Details:
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Capacity: 36,000 BTU
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SEER: 18
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HSPF: 9.5
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Refrigerant: R-32 (low GWP)
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ENERGY STAR® certified
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Grant eligibility: Up to $4,800 through LogisVert
Project Timeline:
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Safe removal of the improperly sized unit
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Adjustment of existing ductwork to fit the new system
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Full commissioning within 48 hours, pressure testing, thermostat calibration
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Delivery of a performance report to the client
Result: a comfortable home, a quiet system, and an immediate drop in electricity costs.
Warning Signs of Poor Sizing
Even before the breakdown, several red flags pointed to a problem:
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Very frequent on/off cycling
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Uneven temperatures throughout the home
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Uncontrolled humidity levels
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Unexplained increase in electricity bills
Best Practices to Follow
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Always request a full heat load calculation before signing an installation contract
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Choose certified installers with local experience, like AirGreen
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Request an analysis of available grants for the proposed equipment
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Make sure the selected system is compatible with existing ductwork
Why Choose AirGreen?
For over 10 years, we’ve been installing central heat pumps in Montréal, Laval, Longueuil, the North Shore, and the South Shore. What sets us apart:
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Rigorous technical expertise
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Certified equipment, eco-friendly refrigerants
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Compliance with electrical, mechanical, and energy efficiency standards
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Full support from quote to annual maintenance
We turned this customer’s bad experience into a long-term solution, with a system sized to last 15 to 20 years, without compromising comfort or efficiency.
A Costly Mistake That Can Be Avoided
This real case clearly shows how a poor HVAC sizing decision can become an expensive burden — not just financially, but in terms of comfort, stress, and lost trust. At AirGreen, we believe a successful installation starts with smart evaluation. That’s why we always include a personalized analysis, careful equipment selection, and professional execution.