Should You Leave Your Furnace Fan On or Auto in Winter in Ontario?
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- 5 days ago
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In Ontario winters, choosing Furnace Fan ON vs Furnace Fan AUTO affects more than comfort. It can change how evenly your home heats, how well your filter works, and how much electricity your blower uses. This Toronto & GTA guide explains the trade-offs clearly—so you can pick the best setting for your furnace and duct system.
Answer Capsule
Most Ontario homes: Keep the fan on AUTO for the best balance of efficiency and comfort.
Switch to ON if you have uneven rooms, allergies/pets, or want steadier air circulation—especially with an ECM/variable-speed blower.
Avoid ON if your home is already too dry, you suspect leaky ducts, or your furnace uses an older PSC motor (often higher fan-only electricity use).
Best compromise: If your thermostat supports it, use Circulate (runs the fan ~10–20 minutes per hour) instead of full-time ON.
What “Fan ON” and “Fan AUTO” Actually Do
Fan AUTO
The blower runs only during a heating call (and typically a short after-run). This is the default setting because it minimizes fan-only electricity.
Fan ON
The blower runs continuously, even when burners are off. This can improve mixing and filtration, but can increase electricity use and may worsen dryness or dust issues in some duct systems.
On vs Auto: Quick Comparison Table (Ontario Winter)
Factor | Fan AUTO | Fan ON |
Comfort / Even heat | Good for many homes | Often better for multi-level homes and hot/cold rooms |
Air filtration | Filters only during heating cycles | More air passes through the filter (better for dust/allergies if ductwork is tight) |
Humidity / dryness | Usually feels less “drying” | Can make dryness more noticeable in winter |
Electricity cost | Typically lower | Can be higher (especially older PSC motors) |
Best for | Most Ontario homes as a safe default | Homes with uneven temps, allergies, newer ECM blowers, circulation needs |
When Fan ON Is a Good Choice in Toronto & GTA Winters
1) Uneven heating between floors or rooms
Two-story homes, finished basements, and older Toronto duct layouts commonly produce temperature swings. Continuous circulation can reduce stratification and improve comfort where heat “pools” upstairs.
2) You want stronger filtration for dust, pets, or allergies
Your filter only cleans air that passes through it. Running the fan more often increases filtration—as long as the filter is sized correctly and changed on time. Use this schedule: Toronto & GTA furnace filter schedule.
3) You have a modern ECM/variable-speed blower
Newer furnaces often circulate at lower watt draw in fan-only mode, making ON (or Circulate) more practical without a big electricity penalty.
When Fan AUTO Is the Better Ontario Winter Setting
1) Your home feels too dry in winter
Ontario winters are dry; more air movement can make dry air more noticeable (static, dry skin, scratchy throat).If dryness is your #1 complaint, AUTO is usually the better choice.
2) You have an older PSC blower motor
Older motors often use more power in continuous operation. If your hydro bill matters, AUTO is the default winner.
3) You suspect leaky returns or dusty ductwork
If return ducts are leaky (common in older homes), running the fan continuously can pull dust from wall cavities/attics more often. In that case, keep AUTO until duct sealing or return improvements are completed.
Commissioning-Grade Homeowner Tip
The “right” fan setting depends on your furnace design, blower motor type, and duct static pressure. A qualified technician can verify the setup using measurable diagnostics—not guesswork—so you get comfort without unnecessary operating cost. If you’re seeing short-cycling, weak airflow, or frequent lockouts, use this guide: Furnace not working in GTA.
Best Practice Recommendation for Ontario Winters
Default: AUTO
Upgrade option: Use Circulate mode if available (best comfort/cost compromise)
Use ON: When you need better mixing/filtration and you have a newer blower or confirmed duct integrity
FAQ: Furnace Fan ON vs AUTO in Ontario Winter
Is it safe to leave my furnace fan ON all the time?
Generally yes, if the system is healthy and installed correctly. The decision is usually about comfort, dryness, and electricity use. If you smell overheating, hear grinding/squealing, or airflow is weak, turn it back to AUTO and schedule service.
Will FAN ON reduce dust in my home?
It can help because more air passes through the filter. But if your returns are leaky or your filter is restrictive, it can backfire. Follow a proper filter schedule and have airflow checked during maintenance.
Does FAN ON help with uneven heating?
Often yes—especially in multi-level GTA homes. If the problem is severe, the real fix may be duct balancing, return improvements, or blower setup.
Will FAN ON increase my bill?
It can. The impact depends on blower motor type and fan speed. ECM/variable-speed blowers typically cost less to run continuously than older PSC motors.
Book Help
If you want the best fan setting for your exact furnace, have us verify blower type, airflow, filter setup, and thermostat configuration.