How to Buy a New Furnace

When you're learning how to buy a new furnace, the most important factors to weigh are the unit’s size, its AFUE efficiency rating, its fuel source and comfort features like a variable-speed blower. Carrier recommends evaluating four key factors: furnace size, efficiency, fuel type, and comfort features such as blower and heating-stage technology. Balancing your budget with long-term energy savings and brand reliability ensures you invest in a system that delivers consistent warmth for decades.

This guide provides a practical Carrier-focused framework for evaluating the types of furnaces available, the ten essential questions to ask when buying a new furnace, and how to locate a qualified dealer for expert furnace installation and regular furnace tune-ups.

Carrier's 4-Step Guide to Buying a New Furnace

Carrier recommends starting with four fundamental considerations when selecting a new furnace:

1. Choose the correct furnace size. A qualified HVAC professional should perform a load calculation based on factors such as your home's size, insulation, windows, climate, and other characteristics—not square footage alone. 

2. Compare AFUE efficiency ratings. AFUE measures how efficiently a furnace converts fuel into usable heat. Higher AFUE ratings generally mean less fuel is required to produce the same amount of heat.

3. Select the appropriate fuel type. Carrier offers furnace solutions using different fuel sources, including natural gas, oil, propane and electricity, depending on the system and application.

4. Evaluate comfort and control features. Features such as variable-speed blowers, multi-stage heating and modulating gas valves can provide more precise temperature control and quieter operation. Carrier's Infinity® 98 Gas Furnace 59MN7, for example, combines a modulating gas valve with a variable-speed blower and offers up to 98.5% AFUE

Questions to Ask Before Buying a New Furnace

Buying a new furnace is a significant investment in your home's infrastructure. Making the right choice impacts your comfort and energy footprint for years to come. By understanding the pros and cons of repairing versus full furnace replacement, analyzing how much a new furnace costs, and planning for maintenance, you can make a confident decision.

Kevin Dickson, president of Energy Services Air Conditioning, Heating and Electrical in Naperville, Illinois, notes that homeowners must weigh several variables to select the ideal system.

"Homeowners should consider their budget, the size of the unit, the unit’s efficiency, the number of stages of the furnace, and the brand reliability when picking out a furnace for their home," Dickson said. 

1. Are there different types of furnaces?

Yes, Carrier has identified the 4 most common furnace types as:

1. Gas Furnaces
2.  Oil Furnaces
3. Electric Furnaces
4. Propane Furnaces

While the fundamental operation (heating air and circulating it through your home) remains consistent, your choice largely depends on fuel availability and efficiency goals.

For most people, the best option is to stick witha furnace that utilizes the same fuel source as your current one. Gas furnaces and oil furnaces are traditional choices, while electric and propane furnaces offer alternatives where natural gas isn't available. Learn more about gas vs. electric vs. oil furnaces.

How to figure out what kind of furnace you have

Your furnace's rating plate tells you most of what you need to know. It's a sticker inside the front door panel. Turn the panel knobs counterclockwise, pull the panel toward you, and look for the model and serial numbers.

On current Carrier furnaces, the model number spells out the basics. Models starting with 58 are 80% AFUE furnaces, and models starting with 59 are 90% AFUE or higher. The third character shows how the furnace heats: S for single-stage, T for two-stage, M for modulating. A 59MN7, for example, is the modulating Infinity® 98.

If you can't reach the rating plate, check the vent pipes. White plastic PVC pipes running out a side wall usually mean a high-efficiency condensing furnace. A metal flue running into a chimney usually means an 80% model. Then look at the fuel source. A gas line and meter point to natural gas, an outdoor tank points to propane or oil, and no fuel line at all points to an electric furnace.

A local Carrier expert can confirm exactly what you have during a service visit and tell you whether it's worth repairing or replacing. Learn more about where to find your serial number.

2. How do I compare energy efficiency between different furnaces?

Carrier recommends comparing furnaces using the AFUE (Annual Fuel Utilization Efficiency) rating, which functions like MPG for a car—the higher the percentage, the more efficient the unit.

All furnaces sold in the United States must display an EnergyGuide label estimating annual operating costs. An 80% AFUE furnace converts about 80% of its fuel energy into usable heat, while Carrier's  Infinity® 98 Gas Furnace offers up to 98.5% AFUE.

For the same amount of delivered heat, moving mathematically from 80% AFUE to 98.5% AFUE would require about 18.8% less fuel. Actual household savings will vary based on climate, fuel prices, home efficiency, equipment operation, and other factors.

3. Are there other features I should consider when buying a new furnace?

Carrier recommends considering comfort features such as variable-speed blowers multi-stage heating and modulating technology. These technologies can help provide more consistent temperatures, quieter operation and more precise heating control.

• A variable-speed blower can adjust airflow to support more consistent comfort and can also assist with air conditioning and dehumidification when used as part of a compatible system.
• Multi-stage furnaces adjust their heating capacity to better match heating demand rather than operating only at full capacity. Modulating furnaces can make smaller adjustments to heating output for more precise temperature control. 

Naturally, the cost of a new furnace will reflect these capabilities, but the long-term comfort dividends are substantial.

4. How do single-stage, two-stage, and variable-speed furnaces compare?

The main difference is how precisely each furnace controls its heat. A single-stage furnace runs at full capacity every time it turns on, a two-stage furnace adds a lower setting for milder days, and a modulating furnace adjusts its output in small increments to hold your exact temperature.

Here’s how each type compares:

• Single-stage: Operates at 100% capacity whenever your home calls for heat. The Comfort™ 96 Gas Furnace pairs a single-stage gas valve with up to 97% AFUE (Annual Fuel Utilization Efficiency) for affordable, reliable warmth.
• Two-stage: Runs at about 60% to 65% capacity most of the time and shifts to 100% when temperatures plummet. The Performance™ 97 Gas Furnace pairs two-stage heating with a variable-speed blower for steadier comfort.
• Modulating: Fine-tunes heat output in small increments instead of simply turning on and off. With up to 98.5% AFUE, the Infinity® 98 Gas Furnace represents the pinnacle of precise temperature control.

“Variable-speed” describes the blower motor that moves warm air through your home, not the burner. Many high-efficiency furnaces pair a two-stage or modulating gas valve with a variable-speed blower for more even airflow.

Daniel Donahue, general manager of Mullen Refrigeration Service in Latrobe, Pennsylvania, notes, “A single-stage furnace operates at 100% capacity whenever it calls for heat, regardless of how much heating is actually needed.”

Two-stage and modulating furnaces cost more upfront, but they can pay long-term comfort dividends through steadier temperatures and lower energy use. Learn more about how a two-stage furnace works and the difference between modulating vs. variable-speed furnaces.

5. What size furnace do I need?

To figure out what size furnace do I need, Carrier recommends having a qualified HVAC professional perform a load calculation to determine the appropriate furnace capacity, measured in British Thermal Units per hour, or BTUh. The calculation considers factors such as your home's square footage, insulation, windows and local climate—not just the physical size of the furnace or the home's square footage.

How to find the right furnace size for your home

To determine the correct capacity, an installing dealer must perform a load calculation assessing your square footage, window quality, insulation levels, and local climate. An improperly sized furnace can reduce comfort and efficiency and may contribute to unnecessary equipment wear. Always rely on a qualified HVAC professional to perform this assessment.

6. What are the average furnace installation costs?

The cost to have a new furnace installed generally ranges between $3,800 and $12,000 covering materials, equipment, and labor. ¹

Variables affecting this price include:

• Fuel type (gas furnaces may cost more upfront than electric)
• Necessary ductwork retrofits
• Venting updates
• Premium features.

Since your furnace is often the hub of your central air system, buying a new furnace is also the strategic time to consider replacing your air conditioner or adding a heat pump for a dual fuel heating system. Contact your local Carrier dealer for a precise estimate tailored to your home's needs.