How Much is a Furnace Installation? 80% vs 95% Efficiency Explained

If your air conditioner (AC) system, coil, and condenser are relatively new, but your furnace is old and failing, you may only need a furnace-only replacement. But how much does that cost?

The Furnace Installation Cost depends heavily on three variables: efficiency level, staging technology, and the complexity of the installation (including necessary code corrections and ductwork adjustments). We break down the rough price ranges for common gas furnace types.

1. The Cost of an 80% Gas Furnace Installation

The “80%” refers to efficiency: 20% of the heat generated is lost out the flue pipe. These systems are typically easier to install, often requiring less labor time (around four hours for one crew) than high-efficiency models.

Single-Stage 80% Furnace

A single-stage furnace runs at 100% capacity whenever it is heating. It’s the most basic and affordable option.

• Rough Installation Cost Range: $3,500 to $4,500.

Two-Stage 80% Furnace

A two-stage furnace operates at two capacity levels (e.g., 70% and 100%), running longer at the lower stage when demand is low. This provides better comfort than a single-stage system.

• Rough Installation Cost Range: $5,500 to $7,500.

Important Consideration: If upgrading to a two-stage system, ensure your existing thermostat is capable of handling two-stage operation; otherwise, a thermostat replacement may be required.

2. The Cost of a 95% Gas Furnace Installation (High-Efficiency)

The “95%” refers to high efficiency, meaning only 5% of the heat is lost out the flue pipe, resulting in significant savings on your gas bill over time. However, these systems are more complex due to condensation.

Single-Stage 95% Furnace

This high-efficiency unit runs at 100% capacity, but extracts maximum heat before venting.

• Rough Installation Cost Range: $4,500 to $5,500. (Slightly more expensive than the 80% single-stage due to the technology and required venting adjustments).

Two-Stage 95% Furnace

This system combines high efficiency with two-stage comfort (low and high capacity).

• Rough Installation Cost Range: $6,500 to $8,500.

Modulating (Variable Capacity) Gas Furnace

A modulating furnace provides the ultimate in comfort and efficiency by continually ramping up and down (e.g., 30% to 100%) to perfectly match demand.

• Rough Installation Cost Range: $8,500 to $9,500.
• Caveat: Modulating furnaces typically require a communicating thermostat and communicating equipment to function optimally. If your existing setup isn’t compatible, this may not be the best option for a furnace-only replacement.

3. Variables That Impact the Final Installation Cost

The prices listed above are rough estimates and depend on several crucial factors that may require additional labor and materials:

Code and Safety Upgrades

When replacing a furnace, the installer must bring the entire system up to current code. This often involves:

• Updating the gas line connection or installing a drip leg.
• Ensuring the flue pipe and venting are sized and installed properly.
• Addressing safety devices, especially if the old unit lacked them.

Ductwork and Airflow Corrections

Regardless of a full or partial system replacement, we always inspect the ductwork. If the existing return air or supply ducts are improperly sized for the new furnace’s blower motor, corrections are necessary. Correct HVAC Ductwork Sizing ensures your new furnace lasts as long as possible and operates efficiently.

Installation Orientation

The location of your furnace (downflow, upflow, or horizontal in the attic) affects labor. Downflow systems (often in mechanical closets) are typically less labor-intensive than those installed horizontally in tight attic spaces.

Important Warning for 95% Furnaces in Attics

We generally do not recommend installing a 95% gas furnace in an uninsulated or cold attic space. High-efficiency furnaces produce condensation (water) that must drain. In freezing temperatures, this drain line can freeze and cause the system to shut down, leading to repeated service calls. While technical protections like heat tape exist, they add to the electric bill, negating some of the efficiency savings.

I hope this breakdown answers your question regarding the Furnace Installation Cost. If you have more specific questions that weren’t covered, please feel free to ask!

If you are in the Oklahoma City metro area and are looking for a furnace-only replacement, you can use our instant estimate feature on our website to get a quote and see the rough costs for your specific needs.

About Yarbrough & Sons Heating, Cooling & Plumbing

Serving Oklahoma City and surrounding areas since 1988, we provide expert HVAC maintenance, repair, and replacement services with a commitment to quality and community care.

Locations:

122 S Main Ave, Blanchard, OK 73010

3601 S Broadway #300, Edmond, OK 73013