Bad setting habits that drive up your wall-mounted air conditioning costs
Summers in Montréal can be brutal, and wall-mounted air conditioners are essential allies for staying comfortable indoors. But did you know that frequent mistakes in how your wall unit is set can unnecessarily double your energy bill? At AirGreen, we’ve identified, through real-life experience, the most costly behaviors—often overlooked—that have a direct impact on your wallet. In this article, we share our expertise acquired from hundreds of wall-mounted air conditioner installations and maintenance services across Montréal, Laval, Longueuil, the North Shore and the South Shore, to help you avoid these pitfalls and get the most out of your HVAC system.
The underestimated impact of improper settings
No matter how efficient your wall-mounted air conditioner is, it can become an energy pitfall if not used properly. The problem usually isn’t the machine—it’s how it’s used day to day. As specialists in residential and commercial HVAC installations, we often come across the same errors made by our customers.
Setting the temperature too low: a costly mistake
One of the most common habits is setting the temperature very low, often between 17°C and 19°C, thinking it will cool the room faster. In reality, this just forces the compressor to run at full capacity unnecessarily, without any real speed advantage. The system won’t cool faster—it will just consume a lot more electricity and wear out more quickly.
Our advice:
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Set your wall-mounted air conditioner to 23°C or 24°C, the ideal range for comfort and reasonable consumption.
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Use the timer function to match the cooling to your actual presence in the room.
Misusing the automatic fan mode
Some wall units offer an automatic fan mode. But in highly variable environments—like homes facing south or condos with large windows—this mode can backfire. It causes frequent on/off cycles that prematurely wear down internal components and increase power usage.
Our recommendations:
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Choose a manual mode with a constant fan speed.
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Adjust the airflow direction so that cool air isn’t blocked by furniture or blown directly onto a wall.
Clogged filters: a silent efficiency killer
Even the best wall-mounted air conditioner brands like Fujitsu, Gree, Sharp, or Mitsubishi can’t make up for neglected HVAC maintenance. A dirty filter reduces airflow, forcing the system to consume more energy for weaker performance.
What we see in the field:
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Units in Montréal and Laval with over 30% loss in efficiency due to clogged filters.
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Summer energy bills rising by more than $100/month for clients who skipped maintenance.
AirGreen tip:
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Clean filters at least once every 4 to 6 weeks during the warm season.
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Call a professional for a deep annual cleaning.
Never turning off your wall-mounted AC: myth or fact?
Some people believe it’s more economical to let the unit run continuously rather than turning it off when leaving. This can be true... but only if the unit is smartly programmed with sensors or a timer. Otherwise, it’s just unnecessary power consumption.
Best practice:
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Activate the energy-saving mode.
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Use a smart thermostat or Wi-Fi controller, as we often recommend during our HVAC installations in Longueuil and the South Shore.
Poor positioning of the sensor or remote
Some units have sensors built into the remote control. If it’s placed too close to a window, electronic device, or heat source, it sends incorrect signals to the unit.
What our technicians have observed:
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AC cycles run too frequently due to overestimated room temperatures.
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Differences of more than 3°C between actual room temperature and the one perceived by the system.
Using the dehumidifier mode with no real need
The "Dry" or dehumidification mode is helpful on humid days, but overusing it leads to unnecessary air cooling and higher power consumption.
AirGreen tip:
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Only activate it when humidity goes above 60% (you can measure this with a hygrometer).
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Otherwise, stick to standard cooling mode.
A customer case in Montréal: from energy waste to optimized settings
Recently, during an installation of a Sharp 18,000 BTU wall-mounted air conditioner in a condo in Plateau-Mont-Royal, our client mentioned that their old unit was driving their bills through the roof. After analyzing the previous system, we identified the following errors:
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Constant temperature setting at 17°C
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No timer or automatic regulation
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Filters not cleaned in 2 years
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Remote placed on top of a microwave (heat interference)
With our intervention:
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Installed a new high-efficiency Sharp ZU1 wall-mounted air conditioner
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Customized settings, properly positioned sensor
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Timer programmed for when the client is away
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Full explanation provided to the client
Two months later: a 42% reduction in their electricity bill compared to the previous year.
What you can do today
Here are practical steps you can take immediately:
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Check the programmed temperature on your unit
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Clean the filters
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Set up appropriate time schedules
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Avoid placing the remote near heat sources
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Call AirGreen for a maintenance service or a personalized consultation
Why choose AirGreen for your wall-mounted air conditioner
At AirGreen, we don’t just sell and install wall-mounted AC systems in Montréal, Laval, Longueuil, the North Shore and the South Shore. We guide each customer through their home energy optimization. Our technical teams are trained to help you get the most efficient settings, well beyond installation day.
We also offer:
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Annual HVAC maintenance
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Expert repairs for wall-mounted air conditioners
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Installations eligible for LogisVert grants up to $2,172
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Thermal assessments of your home
Don’t let poor settings drive up your energy bill
A wall-mounted air conditioner is a smart investment—but only if it’s used the right way. At AirGreen, we believe every customer deserves a system that is both high-performance and economical. Contact us today to optimize your settings, schedule an HVAC maintenance visit, or discuss our wall-mounted installation options with grants in Montréal, Laval, Longueuil, the North Shore and the South Shore.