When should I switch from AC to heat?

Great timing question for Ottawa homeowners! The short answer is: switch to heat when overnight temperatures consistently drop below 15°C (59°F), which in Ottawa typically happens in late September to early October.

There's no single magic date, but your comfort is the best guide. Most people find they need heating when daytime highs stay below 18°C and nights dip into single digits. Ottawa's climate can be unpredictable in the shoulder seasons — you might need heat one week and AC the next in September, so don't feel locked into one mode.

For homes with a heat pump, the transition is seamless — the system automatically switches between cooling and heating modes. For traditional gas furnace + central AC setups, you're simply adjusting your thermostat from "cool" to "heat" mode. There's no mechanical switchover required; both systems operate independently.

Ottawa-specific timing tends to be earlier than most Canadian cities expect. Our valley location means cold air settles overnight even when days are mild. A good rule of thumb: if you're closing windows at night by late September, it's time to switch.

Before firing up your furnace for the first time each fall, it's worth doing a quick check — replace your air filter, make sure vents aren't blocked, and listen for any unusual sounds when it first kicks on. A burning smell for the first few minutes is normal (dust burning off), but persistent odours or no heat at all warrant a call to a technician.

Fall is also the ideal time for an annual furnace tune-up before the heating season hits. A licensed technician will inspect your heat exchanger, check gas pressure, test safety controls, and make sure you're running efficiently heading into an Ottawa winter. Tune-ups typically run $150–$200 and can catch problems before they become expensive mid-January breakdowns.

If your furnace hasn't been serviced recently, Ottawa HVAC Pro offers fall maintenance tune-ups — it's the best $150–$200 you'll spend before winter arrives.