Furnaces

AFUE numbers tell the real story about your heating bills. This rating shows what percentage of your fuel money goes toward heating your house versus getting wasted up the chimney. A 90% AFUE furnace turns 90 cents of every fuel dollar into heat for your home. Skip anything below 85% AFUE; it's throwing money away. For cold climates, go 90%+ or don't bother upgrading.

Basic motors work like old light switches – full blast or nothing. Variable-speed motors adjust power output to match what your home actually needs. They run longer cycles at gentler speeds, which gives you steadier temperatures and cleaner air. Buy variable-speed if your budget allows. Your electric bills can drop $200-$300 annually.

Standard steel heat exchangers get the job done and keep costs reasonable. Stainless steel lasts longer and handles temperature swings better, making it worth the extra money when you're planning to stay in your home for many years.  Working with manufacturers taught me that stainless steel heat exchangers withstand thermal cycling much better than regular steel. Test data shows they last 20+ years in normal conditions. Aluminized steel offers middle-ground pricing and durability. Don't waste money on fancy coatings; they're marketing fluff.

Basic furnaces (80% efficiency) use your existing chimney and hot exhaust gases. High-efficiency models (90%+ efficiency) cool exhaust gases so much that they require plastic pipes going through your wall. I've seen installations where homeowners wanted high-efficiency but couldn't use it because their furnace room had no exterior wall access. This affects installation costs and where you place the furnace.

Signs: No heat, cold air, or nothing at all

Try these first:

• Check thermostat batteries and settings
• Look at your circuit breaker – might have tripped
• Replace dirty air filter that could be blocking airflow
• Check that gas valve is on (gas models)

Call someone when: Basic fixes don't work, you smell gas, or electrical parts look damaged

Signs: Big temperature differences between rooms, uneven heating

Try these first:

• Open all vents and remove anything blocking them
• Install a new air filter if the old one's dirty
• Adjust duct dampers when you get access to them

Call someone when: Problems stick around after basic fixes – could be ductwork sizing or blower issues

I've read about cases where return ducts collapse in crawl spaces, causing exactly these symptoms.

Signs: Banging, rattling, squealing, or grinding when the furnace runs

Try these first:

• Tighten loose panels or access doors
• Hunt for debris around outdoor exhaust vents
• Replace air filter when it's really dirty

Call someone when: Grinding, squealing, or loud banging continues – these point to failing blower motors or heat exchanger problems

What furnaces actually cost:

• Equipment: Basic $1,500-$3,000, mid-range $2,500-$4,500, high-efficiency $3,500-$6,000
• Installation: Professional work adds $1,000-$3,000 depending on complexity, ductwork changes, and local rates
• Total: Most people pay $3,000-$8,000 for complete replacement

Contractors mess this up all the time. They wing it or use rules from 1985. Oversized furnaces turn on and off constantly, waste fuel, and heat rooms unevenly. Undersized units run nonstop but never quite keep up when it gets really cold.

Contractors must use Manual J calculations to determine the correct size, measured in BTUs per hour. Homes generally need 30-60 BTUs per square foot, though drafty older homes demand more while well-insulated newer construction needs less.

Don't let anyone guess at sizing , I've heard of too many problems from contractors who eyeball estimates instead of doing proper calculations.

As you're getting quotes for a new furnace, ask each HVAC company these questions: 

• What size furnace does my home need based on a load calculation?
• How do you handle permits and inspections required by local codes?
• What warranty coverage comes with the equipment and your installation work?
• Give me references from recent furnace installations in my area
• Break down your pricing – what's included and what costs extra?

Your furnace connects to other systems:

• Central air: Furnaces and AC usually share ducts and fans, so replacing both at once saves money. My industry experience shows manufacturers offer better pricing on packages.
• Humidifiers: These hook up to your furnace and add moisture when winter air gets bone dry. You'll be more comfortable and get less static shock. For dry climates and harsh winters, I recommend them for homes over 1,800 square feet.
• Air filters and UV lights: These work with your furnace to clean air throughout your home. In my experience, these systems help people with allergies.

Ready to find the right furnace for your house? Smart HVAC USA connects you with local HVAC pros who'll figure out exactly what you need and give you recommendations that fit both your home and your wallet.