Yes — upgrading an older furnace to a modern high-efficiency model is one of the most impactful energy improvements a Denver-area homeowner can make. Today’s top furnaces achieve Annual Fuel Utilization Efficiency (AFUE) ratings of 95–98%, meaning nearly all the gas burned becomes usable heat. An older mid-efficiency unit with an AFUE of 80% wastes about one dollar out of every five spent on gas. In Colorado’s cold winters, that gap adds up quickly on your Xcel Energy bill.

What AFUE Actually Means for Your Energy Bill

AFUE stands for Annual Fuel Utilization Efficiency — it is the percentage of fuel that becomes heat for your home. A furnace rated 80% AFUE converts 80 cents of every dollar of gas into warmth; the other 20 cents escapes up the flue as exhaust. A 96% AFUE unit cuts that waste to just 4 cents on the dollar. The older your current furnace, the bigger the potential savings: units from the 1990s or early 2000s were often rated 60–70% AFUE, and wear over time degrades even that number further.

High-Altitude Considerations Specific to Colorado

Denver sits at roughly 5,280 feet above sea level, and altitude affects combustion. Gas appliances are typically rated at sea-level conditions, so a furnace installed at Denver’s elevation is slightly de-rated by manufacturers — usually around 4% per 1,000 feet. A properly sized and altitude-adjusted high-efficiency furnace accounts for this and still dramatically outperforms an aging unit. Done’s technicians perform Manual J load calculations that factor in Colorado’s altitude, climate zone, and your home’s insulation levels to ensure the new furnace is sized correctly — not just swapped in at the same BTU rating as the old one.

Variable-Speed and Two-Stage Technology

Beyond AFUE, newer furnaces offer variable-speed blower motors and two-stage or modulating burners that dramatically improve comfort and efficiency. Instead of blasting on at 100% and then shutting off, a two-stage furnace runs at a lower stage — say 60–65% capacity — most of the time. That means longer, gentler heating cycles that distribute heat more evenly, reduce temperature swings, and run more quietly. Variable-speed blowers also move more air with less electricity than older single-speed motors, contributing additional savings on your electric bill.

Rebates and Financing That Offset the Upfront Cost

Xcel Energy and other Colorado utilities periodically offer rebates for qualifying high-efficiency furnace installations — worth checking before you purchase. Federal tax credits for efficient home heating equipment may also apply depending on the unit’s specifications and the current tax year (verify with your tax advisor, as these programs change). Done can walk you through available incentives and offers flexible financing options so you are not choosing between a warm house and your budget.

When Upgrading Makes the Most Financial Sense

The upgrade calculus favors replacement most strongly when your current furnace is 15 or more years old, has needed significant repairs in the past two years, or carries an AFUE below 80%. If your system is already relatively new and well-maintained, a tune-up and filter discipline may be all you need. Done will give you an honest assessment — including what your payback period on a new unit would look like based on your current equipment’s condition.

  • Old 60–70% AFUE unit: substantial savings potential with a modern 95–98% model
  • Two-stage / modulating burners reduce temperature swings and noise
  • Variable-speed blowers cut electricity use compared to single-speed motors
  • Altitude de-rating must be factored into sizing at Denver elevations
  • Utility rebates and federal tax credits may reduce net cost

If your furnace is aging and your heating bills keep climbing, it may be time to explore what a new system would cost and save. Learn more about furnace installation and furnace maintenance from Done, or contact us for a no-pressure efficiency assessment of your current setup.