Quick answer
Beyond rate increases, the usual culprits are an aging or poorly maintained furnace losing efficiency, a clogged filter forcing longer run times, leaky ductwork dumping heated air into the basement, air leaks around doors and attic hatches, and thermostat habits like heating an empty house. A furnace tune-up, fresh filter, duct sealing, and a programmable schedule are the highest-return fixes.
Heating bills are high this winter for one of two reasons: the price per cubic metre went up, or your house burned more cubic metres — and only the second one is yours to fix. The bill separates them. Compare your usage in m³ (or kWh, if you heat electrically) against the same month last year in your utility's online portal; if usage itself jumped more than the weather explains, something in the house changed. Here's where to look.
Read the bill before you blame the furnace
- Pull consumption in cubic metres for the same billing period last year — Enbridge's portal shows the two side by side.
- Check whether the meter read is actual or estimated. A run of estimates followed by a true read produces one enormous bill that is really three months of catch-up.
- Separate delivery, storage and carbon charges from the gas itself; fixed charges rise even when you burn nothing.
- Adjust for weather. A January that averaged a few degrees colder pushes usage up on its own — Environment Canada's monthly summaries for Toronto Pearson or Hamilton make the comparison quick.
- If you heat with a heat pump, do the same exercise on the hydro bill; a jump there has its own suspect list below.
HVAC causes, most common first
- Clogged furnace filter — restricts airflow, lengthens run times, and can cut efficiency dramatically. A $15 filter is the highest-return fix 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 and cools the heat exchanger between burns
- A failing heat pump quietly falling back to electric resistance heat — if you have a heat pump and hydro bills exploded, check this first
What era of house you own predicts where the heat goes
- 1950s–60s bungalow: uninsulated block basement walls and thin attic insulation; the 60,000 BTU furnace may be fine while half its heat leaves through the foundation and rim joist.
- 1970s–80s subdivision: windows were replaced decades ago, but the attic often still sits near its original insulation depth and the rim joist was never sealed.
- 1990s builder home: the original 80% AFUE mid-efficiency furnace is now past 25 years and venting into a chimney — the furnace swap is the single biggest gas saving available.
- 2000s+ new build: tight and well insulated, so a high bill usually traces to settings — a schedule nobody programmed, a humidifier stuck open, or a blower set to run continuously.
Building-envelope causes
- Attic insulation below R-50 — the common target for our climate; topping up is one of the strongest-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.
High-bill questions we get every January
- Why is the hydro bill up too? A furnace blower switched to ON runs 24 hours a day, and an older PSC motor on continuous duty adds real kilowatt-hours. Set it back to AUTO unless you have a reason.
- Is it cheaper to leave the heat on all day? No — an eight-hour setback burns less gas than holding temperature, because heat loss scales with the indoor-outdoor difference. Heat pumps are the exception.
- Can the thermostat itself be the problem? A thermostat mounted on a cold exterior wall or above a supply register misreads and over-runs the furnace; relocating it is a small job.
- Could the gas meter be wrong? Rarely — check for an estimated read first, then ask the utility for a meter check if consumption still makes no sense.
- Is an energy audit worth it? A registered energy advisor's blower-door test finds the leaks you cannot see, and some rebate streams for envelope work require the audit anyway.
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 and Hamilton.