More and more high-efficiency wall-mounted air conditioners are flooding the market. Yet, many residents in Montréal, Laval, Longueuil, the North Shore, and the South Shore are noticing a worrying increase in their Hydro-Québec bills, even after investing in an energy-efficient unit. At AirGreen, we’ve encountered this issue multiple times during our HVAC service calls. In this article, we’ll take a deep dive into the reasons behind this paradox, backed by our field experience, real-life installations, and clear technical explanations.
A Promise of Energy Efficiency… That Falls Short
When a homeowner installs a high-efficiency wall-mounted air conditioner, they naturally expect to see substantial savings on their electricity usage. However, several factors can sabotage these savings — even with a high-performance unit like a Gree Lomo, Sharp ZU1, or Fujitsu KZCA.
Poor Sizing: A Common Mistake That Costs You
One of the most frequent problems we see with our clients is improper sizing of their unit. A wall-mounted air conditioner that is too large or too small will:
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Start and stop too frequently (short-cycling),
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Use more energy to reach a stable temperature,
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Speed up compressor wear.
Real example from Laval: a client had a 24,000 BTU wall unit installed by another company in a space that only needed 12,000 BTU. The result? Constant short cycling, excessive energy use, and ineffective cooling. We replaced the unit with a properly sized Fujitsu 12K KZAH, and their Hydro bill immediately dropped by 28%.
Air Leaks and Poor Insulation: The Invisible Enemies
An air conditioner, even a wall-mounted one, isn’t magic. If it’s installed in a poorly insulated home with multiple air leaks, it will compensate by consuming more electricity.
At AirGreen, we systematically carry out a thermal analysis of the space before every installation. For example, we advised a client on the South Shore to add attic insulation before we installed their Sharp ZU1 18,000 BTU. Thanks to this preventative measure, the system now operates at just 65% of its capacity—even during a heat wave.
Poor Installation: Efficiency Cut in Half
Unfortunately, sloppy installations are all too common:
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Improper drain angle,
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Wall-mounted unit placed in direct sunlight or poorly ventilated area,
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Refrigerant lines that are too long or poorly connected.
A bad installation can reduce energy efficiency by up to 40%, based on our assessments. At AirGreen, we strictly follow CSA/B149 line length standards, ensure strategic placement of indoor and outdoor units, and guarantee airtight sealing at every connection point.
Poor HVAC Maintenance = Sharp Efficiency Drop
Maintenance is often neglected. Yet a dirty filter or clogged coil forces the motor to work harder.
In 2024 alone, we performed over 350 HVAC maintenance calls in Montréal, with nearly 70% of the units significantly impacted by buildups of dust, pollen, or mold.
That’s why we offer an annual HVAC maintenance plan that includes full cleaning, pressure checks, and performance testing. The result? Fewer breakdowns, lower consumption, and a longer lifespan for your equipment.
Inefficient Usage: The Paradox of the Comfort Zone
Some user habits have a direct impact on your Hydro bill:
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Cooling the entire house to 20°C in the middle of summer,
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Leaving doors open between cooled and non-cooled areas,
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Using “High” mode all the time,
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Letting the system run overnight even when no one is home.
AirGreen Tip: setting your system to 24°C in summer with optimized airflow gives excellent comfort without excessive consumption.
Subsidy Promises vs. Reality on the Ground
Certain brands like Gree or Fujitsu are eligible for Hydro-Québec’s LogisVert rebates, making them very attractive. But beware: an eligible unit won’t automatically deliver savings if the installation or usage is not optimized.
Real Case in Montréal: The Trap of a Misunderstood Model
A family in Rosemont contacted us after their bill went up 40% following an installation. They had a Tosot 18,000 BTU wall-mounted unit installed by an uncertified contractor. Not only was the unit oversized, but it had also been set to run permanently on “turbo” mode. After reconfiguration, recalibration, and thermostat replacement, their consumption dropped below what they were using before the installation.
How AirGreen Tackles These Pitfalls Head-On
At AirGreen, we are committed to:
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Accurately assessing the thermal needs of each space,
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Installing only properly sized wall-mounted air conditioners,
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Delivering HVAC installation in line with CSA/B149 standards,
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Educating our clients on optimal usage of their systems,
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Offering proactive HVAC maintenance services with personalized reminders.
Brands We Install
We offer a wide selection of top-performing brands:
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Fujitsu (KZAH R-32 series, RL2),
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Gree (Lomo, U-Crown, Extreme),
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Tosot,
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Sharp (ZU1),
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Zephyr, Comfortmaker, Haxxair, and more.
All are compatible with Hydro-Québec subsidies, provided they are properly installed and used intelligently.
Conclusion: A Wall-Mounted AC Is a Great Choice—If Done Right
A high-efficiency wall-mounted air conditioner isn’t a guaranteed ticket to savings. The key lies in a combination of factors: choosing the right model, professional HVAC installation, regular maintenance, and smart usage habits.
At AirGreen, we do everything we can to ensure each client enjoys optimal comfort with no surprises on their Hydro bill. We’ve completed over 1,200 installations across Montréal, Laval, Longueuil, the North Shore, and the South Shore, with a customer satisfaction rate that reflects our expertise.
Want to reduce your electricity usage without sacrificing comfort? Contact us today for a personalized evaluation.