A replacement furnace sized for the house you live in now
Heat load, duct capacity and venting all shape the right furnace. We measure each one before recommending equipment.
Follow a furnace swapWhat goes into choosing a new furnace
A furnace replacement is more than swapping one box for another. The new unit has to deliver the right amount of heat for your home, move the correct volume of air through your existing ducts, vent its exhaust safely and fit the space available. Getting all four right is what separates a furnace that quietly keeps the house comfortable from one that roars, overheats or leaves rooms cold.
Efficiency is the first major decision. Furnaces rated around 80 percent AFUE vent through a traditional flue, while high-efficiency condensing furnaces rated 95 percent and above vent through plastic pipe and need a condensate drain. The higher-efficiency option lowers gas use, and whether its extra cost pays back depends on your fuel prices, climate and how long you plan to stay in the home.
We measure the home, inspect the ducts and venting, and present options side by side with flat installed prices so the comparison is clear.
- Efficiency options
- 80 percent and 95 percent plus AFUE
- Blower choices
- Single, two-stage and variable speed
- Start-up
- Gas pressure, temperature rise, combustion
When it is time to stop repairing the old furnace
These signs, especially in combination, point toward replacement.
A cracked heat exchanger
The heat exchanger separates combustion gases from the air you breathe. A crack is a safety concern, and on an older furnace replacement is usually the recommendation.
Age beyond 15 to 20 years
Many gas furnaces last in that range. Past it, parts become scarcer and efficiency falls well behind current equipment.
Frequent ignition or control failures
Repeated service calls for igniters, control boards and inducer motors add up quickly on an aging unit.
Rooms that never get warm
Uneven heat can come from an undersized furnace, a weak blower or duct problems. A replacement is a chance to correct all three.
Rust, soot or scorch marks
Signs of corrosion or burning around the burner compartment or flue suggest combustion or venting problems that deserve a close look.
Rising gas bills without explanation
A furnace losing efficiency uses more fuel to deliver the same heat. Comparing seasons can reveal a steady decline.
Replacing a furnace, step by step
Load calculation and duct review
We calculate the heating load and check the ducts and return air capacity so the new furnace's blower can move the air it needs.
Proposal with options
You see furnace choices at different efficiency and blower levels, each with a flat installed price and warranty details.
Removal and venting work
The old furnace is removed, and venting is updated for the new unit, including plastic venting and condensate drainage for condensing models.
Installation and connections
The furnace is set level, connected to gas, electrical and ductwork, and the transitions are sealed to prevent air leaks at the cabinet.
Start-up and testing
Gas pressure, temperature rise, static pressure and combustion are measured and adjusted to the manufacturer's range before handoff.
Why temperature rise and static pressure get measured
Every furnace has a temperature rise range printed on its rating plate, which is the difference between the air entering and leaving the unit. If the rise is too high, the furnace is not moving enough air, often because of undersized ducts or a restrictive filter, and the heat exchanger runs hotter than it should, shortening its life. If the rise is too low, the air coming from the registers feels lukewarm. Measuring and adjusting blower speed to keep the rise within range protects the equipment and improves comfort.
Static pressure measures how hard the blower is working against the ductwork. Many existing duct systems were never sized for the airflow a modern furnace or a matched air conditioner needs. High static pressure causes noise, reduces airflow and makes variable-speed blowers use more electricity. When we find high static, we explain the options, such as adding return air or enlarging a restrictive section, so the new furnace can perform as designed.
About variable-speed blowers
Variable-speed blowers ramp up gently, run longer at lower speeds and help with humidity control in summer when paired with air conditioning. They are quieter and more even, and they perform best in duct systems with reasonable static pressure.
Signs it is time and what a replacement involves
Furnaces rarely fail without warning. Rising repair frequency, uneven heating, longer run times and higher gas bills are common signs that a furnace is nearing the end of its useful life. Safety issues are more urgent: a cracked heat exchanger, rust through the cabinet, flame rollout or persistent carbon monoxide readings are reasons to stop using the furnace and plan replacement.
When replacement is the right choice, the process begins with sizing. A load calculation determines how much heat the home needs, and the duct system is evaluated to make sure it can support the new furnace's airflow. Efficiency is the next decision. High-efficiency condensing furnaces vent through plastic pipe and need a condensate drain, while standard efficiency furnaces can use existing metal venting if it meets current requirements.
On installation day, gas and power are shut off and the old furnace is disconnected and removed. The new furnace is set, connected to the ductwork, gas line, venting and electrical supply, and the condensate drain is installed if needed. If the air conditioner coil sits on the furnace, it is carefully reconnected or replaced if it is no longer compatible.
Startup includes checking gas pressure, temperature rise across the heat exchanger, venting draft, safety switches and carbon monoxide levels. The installer sets the blower speeds for heating and cooling, configures the thermostat and shows you how to change filters. You leave with a furnace that is sized, installed and verified to operate safely.
Furnace replacement mistakes
These are the most common causes of poor performance after a furnace replacement.
Oversizing for extra comfort
A furnace that is too large heats quickly, shuts off and cycles often, leaving temperature swings and extra wear instead of better comfort.
Ignoring venting requirements
High-efficiency furnaces need proper plastic venting and condensate drainage. Improper venting can cause lockouts or safety concerns.
Overlooking ductwork limits
A new variable-speed furnace cannot overcome restrictive ducts. Static pressure testing identifies problems that should be corrected.
Forgetting the air conditioner coil
Furnace height, coil compatibility and refrigerant type affect whether the existing coil can stay or must be replaced.
Skipping combustion testing
Gas pressure and combustion readings confirm the furnace burns safely and efficiently. They should be recorded at startup.
What moves a furnace replacement price
- Efficiency rating
- A 95 percent plus condensing furnace costs more than an 80 percent unit, and its venting and drainage add installation work.
- Blower and burner staging
- Two-stage burners and variable-speed blowers improve comfort and quietness at a higher equipment cost.
- Venting changes
- Moving to a condensing furnace may leave a water heater alone in the chimney, which can require a liner to vent safely.
- Duct and return corrections
- Adding a return or fixing a restrictive transition during installation costs less than doing it later.
Furnace replacement questions
- Should I replace my air conditioner at the same time?
- If the air conditioner is old or uses R-22, replacing both together ensures the indoor coil, furnace blower and outdoor unit are properly matched. If the air conditioner is newer, a furnace alone can make sense as long as the coil fits the new cabinet.
- Is a bigger furnace better for cold snaps?
- No. An oversized furnace short cycles, creates temperature swings and can overheat if the ducts cannot handle its airflow. A properly sized furnace handles cold weather by running longer.
- What is a cracked heat exchanger and is it dangerous?
- The heat exchanger keeps combustion gases separate from household air. A crack can allow those gases, including carbon monoxide, to mix with circulating air. Every home with fuel-burning equipment should have working carbon monoxide alarms.
- How long does installation take?
- Most furnace replacements are completed in a single day. Conversions that involve new venting, a chimney liner or duct modifications can take longer.
- Will I need a permit?
- Furnace replacement typically requires a mechanical permit, and gas work may need inspection. We handle the permits that apply in your jurisdiction.
Replace the furnace on your schedule, not in a cold emergency
Get a load calculation and a written furnace proposal with flat installed prices.