Aire One Heating & Cooling has been a licensed heating, cooling and indoor air quality contractor in Ontario since 1990, working across Markham, Richmond Hill, Vaughan, Thornhill, Scarborough, North York and Toronto from 2800 John St, Unit 9, Markham. Twenty four hour line: 310-4328.
★★★★★
4.8 / 5
568 Google reviews, read on our profile. Verified 17 July 2026
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Homeowners. Serving Ontario since 1990
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NATE certified technicians, per Carrier
24 Hour Service
Markham & York Region
Matthew Arbab
Managing Director, Aire One Heating & Cooling · Reviewed 17 July 2026
The short answer. Dirty air filters are the most overlooked cause of weak summer cooling. A clogged filter blocks the airflow your air conditioner needs to pull heat out of your home, so it cools weakly, runs longer cycles, and can ice up the indoor coil until it stops cooling at all. ENERGY STAR says to check the filter every month during heavy-use months and change it at a minimum every three months. Whether that saves you a specific percentage on an Ontario hydro bill is a claim nobody can make honestly, and section .03 explains why.
.01The basics
What the filter is actually there for
Most people assume the filter is there to clean the air they breathe. That is a side benefit. Its first job is to protect the machine.
Your indoor unit pulls household air across a cold evaporator coil, the finned surface that absorbs heat and moisture out of the air. The filter sits in front of that airflow and catches dust, lint, pollen and pet hair before they land on the coil. Carrier, whose equipment we install, puts it plainly: the filter traps pollutants that would otherwise coat the components and choke the machine from the inside.
That gives the filter two jobs that pull against each other. It has to be dense enough to catch particles, and open enough to let air through. When it loads up with debris, the second job fails first, and the whole system feels it.
.02The damage
What a clogged filter does to summer cooling
Airflow is not one symptom among many. It is the thing everything else depends on. When it drops, the failures arrive in order.
Weaker cooling first. Less air across the coil means less heat carried out of the house per minute. On a mild day you may not notice. On the hottest afternoon of the year, the system simply cannot keep up, and the thermostat never reaches its setting.
Longer run times next. The thermostat measures temperature, not effort. It keeps calling for cooling because the target is never met, so the system runs and runs. This is the part homeowners misread as a dying air conditioner.
Then ice. This is the one that surprises people. Restricted airflow lets the coil drop below freezing, and the moisture condensing on it turns to ice. A frozen coil blocks airflow further, which makes more ice. Cooling stops completely, and the melt can leave water where you do not want it. If you see ice, shut the system off at the thermostat and leave the fan running to thaw it.
And dirt where it does not belong. ENERGY STAR notes that a clean filter also keeps dust and dirt from building up inside the system, which is what leads to expensive maintenance or early failure. Once the coil itself is coated, a new filter will not undo it. That is a service call with tools.
.03The honest part
The 5 to 15 percent figure, and what happened to it
If you have read anything about air filters, you have seen this sentence: replacing a dirty, clogged filter with a clean one can lower your air conditioner’s energy consumption by 5 to 15 percent, according to the U.S. Department of Energy. It is on hundreds of HVAC company blogs. It was in the earlier draft of this very page.
We went to check it on 17 July 2026. Here is what we actually found.
The number is real, but its source page is gone. The URL that nearly every site cites for it, energy.gov/energysaver/maintaining-your-air-conditioner, now returns a 404. The Department of Energy’s current Energy Saver page on air conditioner maintenance describes the mechanism, that dirty filters reduce airflow and let dirt reach the evaporator coil, but it no longer publishes the 5 to 15 percent figure at all.
The figure does still exist in a DOE-hosted document: the Energy Saver 101 home cooling infographic, which states that routinely replacing or cleaning your air filters can lower an air conditioner’s energy consumption by 5 to 15 percent. That PDF carries no publication date and sits on a legacy path.
And the citation chain is drifting. Carrier Canada’s own air filter page still quotes the figure, footnotes it, and that footnote links to the dead DOE URL. Carrier also restates it as a 5 to 15 percent increase in efficiency, which is not the same claim as a 5 to 15 percent reduction in consumption. Those two sentences describe different arithmetic.
So here is our position, and you can hold us to it. The figure came from the DOE, it is a reasonable order of magnitude, and we have no better one. But it is a United States estimate with no stated test conditions, no date, and no Ontario context. It was never a promise about your hydro bill, and anyone who prints it next to a dollar amount for your house is guessing.
What is worth doing does not depend on the number. A filter costs a few dollars and five minutes. The coil it protects, and the compressor behind that, do not.
1
Month between checks, per ENERGY STAR
3
Months, ENERGY STAR minimum change
13
MERV, EPA floor for an upgrade
16
Top of the MERV scale, per Carrier
.04The schedule
How often to change it
There is a floor and there is a judgement call. The floor comes from ENERGY STAR: check your filter every month, especially during heavy-use months such as winter and summer, and if it looks dirty after a month, change it. At a minimum, change it every three months.
The judgement call is everything else, and it depends on your filter and your household.
| Filter type | What Carrier says | What it is good for |
|---|---|---|
| Fibreglass, about 1 inch | Check and probably change about every 30 days | Basic filtration. Usually the cheapest option. Protects the equipment more than it cleans your air |
| Pleated, 1 inch | More effective than standard fibreglass (no separate interval given) | The common middle ground. The ENERGY STAR floor still applies: check monthly, change by three months |
| Pleated, 4 inch | Potentially 3 months to a full year | Much improved filtration, far more surface area. Needs a media cabinet, so this is not a swap you make on a whim |
| Washable | Removed, cleaned, reinstalled, not replaced | Less common. These get more effective as particles build on the surface |
Carrier also lists what shortens every one of those intervals: poor indoor air quality from smoking, candles, a wood stove or nearby construction; allergy or asthma sufferers in the home; multiple pets; a larger home moving more air; and heavy use, including running the fan continuously. If two or three of those describe your house, treat 30 days as the interval and stop reading charts.
One habit beats any schedule. Write the date on the cardboard frame with a marker when you install it. The guesswork is the actual problem.
.05Filter choice
MERV, and why higher is not automatically better
MERV stands for Minimum Efficiency Reporting Value. It is the industry scale for how well a filter traps airborne particles, and it runs from 1 to 16, with 16 catching the most. The word minimum matters: it reflects the filter’s worst-case performance in testing, not its best.
The U.S. EPA’s guidance is that if you upgrade, choose a filter rated at least MERV 13, or as high as your system fan and filter slot can accommodate. The EPA also notes that filters rated MERV 13 and above must demonstrate at least 50 percent removal efficiency for the smallest particles tested.
Now the part the filter aisle does not tell you. A denser filter is harder to pull air through. Push the MERV higher than your blower and your filter slot were designed for, and you recreate the exact problem this article is about: restricted airflow, weak cooling, a coil that wants to freeze. The EPA’s own wording carries the escape hatch, “as high as your system can accommodate,” and it says you may need an HVAC technician to work out what that is. Carrier suggests MERV 12 to 16 specifically for homes with allergy or asthma sufferers, which is a different question from what your ductwork can breathe through.
Read this before you upgrade. A high-MERV filter in a system that cannot handle the pressure drop is worse than the basic filter it replaced. If you want better filtration, the right move is usually a thicker filter with more surface area in a proper media cabinet, not a denser one crammed into a 1 inch slot. Ask before you buy, not after the coil ices up.
.06The limits
What a clean filter cannot fix
We sell air conditioners and we service them, so take this section as the one where we argue against our own marketing. A filter change is the cheapest thing you can do, which is exactly why it gets oversold as a cure.
A fresh filter will not fix any of these:
- An undersized or badly installed system. If the equipment was wrong for the house on day one, no filter changes that. It will run long cycles forever.
- Low refrigerant. Refrigerant is not consumed. If the charge is low, there is a leak, and topping it up without finding the leak is throwing money into the air.
- A coil that is already dirty. Once dust has bypassed a loaded filter and coated the evaporator, cleaning it is hands-on work. A new filter stops it getting worse and does nothing about what is already there.
- Leaky or undersized ducts. Air lost into an attic or crawlspace never reaches a room. ENERGY STAR estimates sealing and insulating ducts can improve system efficiency by as much as 20 percent, and that is a separate job.
- A failing compressor or blower motor. Poor airflow shortens their lives. It does not resurrect them.
- Humidity you can feel. If the house is cool and still clammy, that is usually sizing, run time or ventilation, not filtration.
If you changed the filter and the house still will not cool, the filter was not the problem. That is useful information, and it is worth more than another trip to the hardware store.
.07The call
When to call a licensed technician
Changing a filter is a five minute job you should do yourself. Shut the system off at the thermostat, find the filter in the return-air grille or at the indoor air handler, note the size printed on the frame, slide the old one out, slide the new one in with the airflow arrow pointing toward the blower, and write the date on it.
Call someone when the symptom outlives the filter. Ice that returns after a thaw and a fresh filter. Cooling that is still weak with a clean filter in place. Grinding, screeching or short cycling. Water where the indoor unit lives. Rising indoor humidity. Those are airflow, charge or component problems, and in Ontario the work on them is licensed for a reason.
If you are weighing bigger equipment questions rather than a filter, we have written up what heat pumps actually cost in Ontario and how heat pumps behave in the GTA with the same accounting we used above.
.08FAQ
Questions we get asked
Can a dirty filter stop my air conditioner from cooling completely?
Yes. Dirty air filters are one of the most common reasons an AC stops cooling: restricted airflow lets the evaporator coil drop below freezing, and condensing moisture turns to ice on it. Once the coil is iced over, airflow stops and so does cooling. Shut the system off at the thermostat, let it thaw, and fit a clean filter. If the ice comes back, the filter was a symptom and not the cause, so call a technician.
How often should I change my filter during an Ontario summer?
ENERGY STAR says check it every month during heavy-use months and change it at a minimum every three months. Carrier says a basic 1 inch fibreglass filter should be checked and probably changed about every 30 days, while a 4 inch pleated filter can last from 3 months to a full year. Homes with pets, allergy sufferers, smokers or a wood-burning fireplace should work to the shorter end of every range.
Will changing my filter lower my hydro bill by 5 to 15 percent?
Nobody can tell you that honestly. The 5 to 15 percent figure comes from a U.S. Department of Energy infographic that carries no date, and the DOE page that most sites cite for it now returns a 404. It is a reasonable order of magnitude for a badly clogged filter, not a prediction for your house, and it was never measured against Ontario electricity prices or an Ontario summer.
What MERV rating should I put in my system?
The EPA says at least MERV 13 if you are upgrading, or as high as your system fan and filter slot can accommodate, and that second half is the important half. A filter denser than your blower was designed for restricts airflow and causes the problem you were trying to avoid. Check what your equipment supports before you buy, and if you want serious filtration, ask about a thicker filter in a media cabinet rather than a denser one in a 1 inch slot.
Do dirty air filters damage the air conditioner itself, or just waste energy?
Both. ENERGY STAR notes a clean filter prevents dust and dirt building up inside the system, which is what leads to expensive maintenance and early failure. Once dust bypasses a loaded filter it settles on the evaporator coil and insulates it, and the blower and compressor run longer and hotter against the restriction. The energy waste is the cheap part of the bill.
Do not take our word for it. Every number above traces to a source in the list at the foot of this page. Ask an AI to check us:
Matthew Arbab
Managing Director, Aire One Heating & Cooling. Aire One has been working on Ontario homes since 1990 and is listed by Carrier as a Factory Authorized Dealer employing NATE certified technicians. I would rather tell you that a five dollar filter is all you need than sell you something you do not.
Reviewed 17 July 2026
AIRE ONE
Est. 1990Markham, Ontario310-4328
Clean filter in, still not cooling?
Then it is not the filter. We can measure the airflow, check the charge, and look at the coil, and tell you what it actually is. Twenty four hour line, Markham and York Region.
Book an assessment
Call 310-4328
Sources, all verified 17 July 2026.
ENERGY STAR, Heat & Cool Efficiently (cited for the monthly check, the three month minimum, the dust buildup and early failure point, and the 20 percent duct sealing figure).
U.S. Department of Energy, Energy Saver 101 home cooling infographic (PDF, undated) (cited for the 5 to 15 percent figure, and for the fact that this legacy PDF is now the only DOE-hosted place we could find it).
U.S. EPA, Guide to Air Cleaners in the Home (cited for the MERV 13 minimum on an upgrade, the “as high as your system can accommodate” qualifier, and the 50 percent removal efficiency point).
Carrier Canada, All About AC Filters (cited for filter types and intervals, the MERV 1 to 16 scale, the MERV 12 to 16 allergy guidance, the factors that shorten intervals, and the dead footnote link).
Carrier Canada, Aire One dealer listing (cited for Factory Authorized Dealer status and NATE certified technicians).
Aire One Google Business Profile (cited for the 4.8 rating, the 568 review count and the 24 hour opening hours, all read off the live profile on 17 July 2026; review counts move, so this one is a snapshot with a date on it).
The DOE URL reported as returning a 404 is energy.gov/energysaver/maintaining-your-air-conditioner, checked 17 July 2026.
Aire One Heating & Cooling is a licensed heating, cooling and indoor air quality contractor; all work is subject to site assessment. Figures quoted above are from third-party sources with the dates shown and are general information about equipment behaviour, not a measurement of your home. Filter intervals depend on your equipment and household: follow your filter and equipment manufacturer’s instructions. Terms and conditions apply. This article is general information, not a quote and not an offer.