Confused by Furnace Efficiency Ratings? Here’s What They Really Mean

Confused by Furnace Efficiency Ratings? Here’s What They Really Mean


If you’re shopping for a new furnace, you’ve probably seen terms like AFUE rating, high-efficiency furnace, and energy savings thrown around. But what do these numbers mean? More importantly, how do they affect your comfort and utility bills? Let’s break it down in simple terms.

What Is an AFUE Rating?

AFUE stands for Annual Fuel Utilization Efficiency. It’s the percentage of fuel your furnace converts into usable heat. The higher the AFUE, the more efficiently your furnace operates.

  • Older furnaces (55–70% AFUE): Much heat is lost through the chimney or flue.
  • Mid-efficiency furnaces (80–85% AFUE): Less waste, but still some heat loss.
  • High-efficiency furnaces (90–98% AFUE): These systems use almost all their fuel for heating, making them the most cost-effective in the long run.

So, if your furnace has an 80% AFUE, 80% of the fuel goes toward heating your home, while 20% is lost as waste. A 95% AFUE furnace wastes only 5%, keeping more heat inside where it belongs.

Does a Higher AFUE Always Mean Lower Bills?

Not necessarily. While high-efficiency furnaces use fuel more effectively, your overall savings depend on factors like:

✔️ Energy Costs – If you have cheap natural gas, upgrading might not save as much as you expect.
✔️ Home Insulation – A high-efficiency furnace won’t help much if heat is escaping through leaky windows or a poorly insulated attic.
✔️ Usage Habits – If you crank up the heat all winter long, efficiency matters more than if you only use it occasionally.

That said, if you’re looking for long-term savings and a greener home, a high-efficiency furnace is a smart investment.

What’s the Best Furnace for St. Augustine Homes?

In Florida, we don’t deal with harsh winters like northern states, but we still need reliable heating during chilly nights. If you’re considering a furnace in St. Augustine, an 80–90% AFUE model is usually sufficient. Since we don’t use heating as much as cooling, extreme high-efficiency models may not always justify the higher upfront cost. However, if you want the best performance and savings over time, a 95%+ AFUE furnace is worth considering.

Choosing the Right Furnace for Your Home

Before making a decision, ask yourself:

How long do I plan to stay in my home? (Higher AFUE makes sense for long-term savings.)
Do I want to reduce my carbon footprint? (High-efficiency models use less fuel and emit fewer emissions.)
Is my current furnace struggling to keep up? (An upgrade could mean better comfort and lower energy bills.)

For the best results, always work with a professional HVAC contractor who understands climate needs, energy efficiency, and installation best practices.

Need Help? Let’s Talk!

If you’re still unsure about which furnace is right for you, we’re here to help.

Serving St. Johns County since 1988 with quality, hometown service.

Whether you require installation, repair, or maintenance, our technicians will assist you with top-quality service at any time of the day or night. Take comfort in knowing your indoor air quality is the best it can be with MOE heating & cooling services Ontario's solution for heating, air conditioning, and ventilation that’s cooler than the rest.
Contact us to schedule a visit. Our qualified team of technicians, are always ready to help you and guide you for heating and cooling issues. Weather you want to replace an old furnace or install a brand new air conditioner, we are here to help you. Our main office is at Kitchener but we can service most of Ontario's cities


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