Why Is My Heating Bill So High? 10 Things to Check Before Blaming Your Furnace

Heating demand tracks outdoor temperature closely. A month that was several degrees colder on average — or that had a long cold snap — asks your system for far more heat than the same month last year, with no change in the equipment at all.

• Compare this bill to the same month last year, not to last month.
• Check whether your utility shows heating degree days or a weather-adjusted comparison.
• Account for rate changes, which raise the bill even when usage is flat.
• Account for the household: more people home, more hot water, more heat.

Schedules quietly drift. A hold left on from a holiday, a new setpoint someone nudged up, a dead battery that wiped a program, or a fan set to run continuously can all raise runtime without anyone noticing.

• Confirm the current setpoint and the schedule actually in effect.
• Look for a permanent hold or override left in place.
• Check whether the fan is set to ON instead of AUTO.
• Lowering the setpoint while you sleep or are away reduces heating demand, though the amount saved depends on your home, equipment, and climate.

A filter loaded with dust restricts airflow. The blower works against that restriction, the system runs longer to deliver the same heat, and comfort drops. It is the cheapest thing on this list and the one most often overdue.

• Pull the filter and look at it in the light. Visible loading is enough reason to replace it.
• Match the exact dimensions and the airflow specification your equipment calls for.
• Higher filtration is not automatically better — a filter that is too restrictive for your system can reduce airflow and increase runtime.
• Check the manufacturer's documentation, or ask your HVAC contractor what specification suits your equipment.

Sentinel keeps a short list of replacement filters in the Solutions Center, but the right one is the one that matches your system — not the highest rating on the shelf.

Runtime is the most useful thing you can observe yourself. During very cold weather, long cycles can be completely normal — equipment is sized to keep up on a design-cold day, not to idle through it.

What matters is change. A system that used to cycle comfortably at 30°F and now runs continuously at 40°F is telling you something. So is a system that starts, stops after a few minutes, and starts again repeatedly.

• Note roughly how long cycles last and how often they repeat, along with the outdoor temperature.
• Compare that to what you remember from previous winters.
• Short repeated cycling, or continuous running with falling indoor temperature, is worth a professional look.
• Runtime alone does not diagnose a failure — it tells you whether to keep looking.

Basic visual checks only — nothing that requires opening equipment.

• Walk the house and confirm supply registers are open and not blocked by furniture or rugs.
• Confirm return grilles are not blocked, and that they are not caked with dust.
• Note rooms with noticeably weaker airflow than the rest of the house.
• Leave closed dampers, disconnected ducts, and anything inside the equipment cabinet to a professional.

Heat you pay for and then lose through a gap costs the same as heat you use. On a cold, windy day the obvious leaks are easy to find with the back of your hand: door edges, thresholds, window sashes, the attic hatch, and where pipes or wiring pass through exterior walls.

• Replace failed weatherstripping on doors that leak visible daylight.
• Seal obvious gaps around penetrations in exterior walls.
• Never seal combustion-air openings for a furnace, boiler, or water heater, and never close required ventilation.
• Insulated window coverings help on older single-pane windows.

Ducts that run through an attic, crawl space, or unconditioned garage lose heat into a space you are not trying to heat. Leaks at joints and disconnected runs make it worse, and the symptom homeowners notice is usually one part of the house that never gets warm.

Accessible, visible joints in a basement are sometimes within homeowner reach with the right materials. Diagnosing and sealing ducts inside walls, ceilings, or crawl spaces — and measuring how much they actually leak — is professional work.

Heating equipment can only replace the heat your home loses. If the attic is under-insulated, or air moves freely from the house into the attic through gaps around fixtures, hatches, and chases, the system runs longer every single cold day.

• Look at the insulation depth relative to the ceiling joists — if the joists are visible, there is likely room to improve.
• Air sealing generally comes before adding insulation; insulation over open air paths underperforms.
• Uneven melt patterns or ice at the roof edge can indicate heat escaping into the attic.
• Attic work has real hazards. Wiring, fragile ceilings, and low clearance all argue for a professional assessment.

Equipment that has not been serviced in several years often loses efficiency quietly — dirty burners or coils, a drifting blower, a control that no longer stages correctly. Older equipment also starts from a lower efficiency baseline than current models.

Age alone is not a verdict. What matters is the combination of age, condition, repair history, comfort, and what a current diagnosis actually shows. This is exactly the information Sentinel Home keeps in one place, so next winter you are not guessing when the last service happened.

It can — when the real issue is scheduling and control rather than a mechanical problem or a leaky building. ENERGY STAR certified smart thermostats are certified based on field data showing energy savings, and they also give you better visibility into how much your system actually runs.

What a thermostat cannot do is fix a failing furnace, a struggling heat pump, leaking ducts, or an under-insulated attic. Compatibility also matters more than homeowners expect.

Helpful solution for this problem

Higher heating costs driven by scheduling and control rather than equipment failure.

ecobee Smart Thermostat Enhanced

Helpful for

Automatically managing heating and cooling schedules when the thermostat is compatible with the home's HVAC system.

Why homeowners may find it useful

ENERGY STAR certified smart thermostats are independently certified based on field data to deliver energy savings, while also giving homeowners better control and information about HVAC use.

Before choosing one

Confirm compatibility with your specific heating and cooling system, including wiring and any C-wire requirement. Heat pumps and multi-stage or zoned systems need particular attention.

What it won't do

Fix a malfunctioning furnace, heat pump, duct system, or a poorly insulated home.

View Solution

Sentinel Home may earn a commission from qualifying purchases at no additional cost to you. Products appear here because they may help with the problem described — not because of commission.

No. A high bill is a symptom, and most of the causes above have nothing to do with equipment failure. Age is one factor among several.

• Repair history — how often, how recently, and how expensive
• Comfort — whether the home can actually hold temperature
• Efficiency relative to current equipment
• Overall system condition, not just the age on the label
• The cost of the repair actually being proposed
• A current professional diagnosis
• Expected remaining life

Replacing working equipment because of its age is one of the most expensive mistakes a homeowner can make. Get a diagnosis first, then decide.

• System performance has materially changed from previous winters
• The equipment cycles abnormally — very short cycles, or never shutting off
• Rooms cannot maintain temperature no matter the setpoint
• Any gas smell, combustion concern, or carbon monoxide alarm activity — treat that as an emergency first
• Electrical problems, repeated breaker trips, or scorching
• Suspected duct leakage inside walls, ceilings, attics, or crawl spaces
• Repeated failures of the same component
• Anything you cannot inspect safely from outside the equipment

Sentinel's contractor experience is in early access. Until it opens, this routes to Sentinel's guidance and solutions for this system.