Why are my heating bills so high this winter?

A shocking January gas bill has two kinds of causes: the ones you can't control (rates, carbon charges, a brutally cold month) and the ones you can. Before blaming the weather, compare your usage in cubic metres or kWh against the same month last year — your utility's online portal shows this. If usage itself jumped, something in the house changed. Here's where to look.

HVAC causes, most common first

• Clogged furnace filter — restricts airflow, lengthens run times, and can cut efficiency dramatically. A $15 filter is the best ROI in home heating. How often to change it.
• Furnace running out of tune — dirty burners and incorrect gas pressure waste fuel invisibly; an annual tune-up restores it
• Aging equipment — a 20-year-old 80% AFUE furnace burns noticeably more gas than a modern 96%+ unit for the same heat; if yours is old, see whether high-efficiency pays off
• Leaky ducts — typical homes lose 20–30% of heated air through unsealed joints, much of it into basements and walls. Duct sealing is a one-time fix that pays every month.
• Short-cycling — a furnace that starts and stops every few minutes wastes fuel on repeated ignitions; see why furnaces short-cycle
• A failing heat pump quietly falling back to electric resistance heat — if you have a heat pump and hydro bills exploded, check this first

Building-envelope causes

• Attic insulation below R-50 — the GTA standard for our climate; topping up is one of the best-payback upgrades
• Air leaks at doors, attic hatches, pot lights, and basement rim joists — weatherstripping and caulking are weekend jobs
• Uninsulated basement walls — a major loss surface in older Toronto housing stock
• Single-pane or failed-seal windows — drafty but usually last on the payback list despite being most visible

Behaviour and settings

Heating an empty house at 22°C costs real money. A programmable or smart thermostat that sets back 3–4°C overnight and during work hours typically trims heating costs by a high single-digit percentage — more in drafty homes. (One exception: heat pumps prefer smaller setbacks.) Our list of energy-saving tips for Canadian winters covers a dozen more no-cost habits, and smart thermostats automate the discipline.

If usage is up and the basics check out, have the system measured: a combustion analysis during a maintenance visit tells you exactly what efficiency your furnace is actually delivering. ZK Mechanical can also quote what a high-efficiency upgrade would save at your real usage — book a visit anywhere in the GTA.