I had to look into the rising cost of heating my home recently. For someone new to this, I learned a lot quite quickly about something most of us don’t ever think about: how your home stays warm in the winter.

It’s the furnace. Here’s what I learned about how a furnace works and how one is efficient or not.

The good news is that home furnaces are getting more and more efficient over the years. For instance, former mid-efficiency furnaces used to guarantee 78 – 82% efficiency, but as soon as high-efficiency furnaces came into play, the efficiency has escalated to 90 – 98% percent!

What does furnace efficiency mean?

There is an official rating called Annual Fuel Utilization Efficiency (AFUE) that actually helps define and monitor the efficiency of furnaces across the country. As explained by the Department of Energy, the efficient rating works like this. A 80% rating means that only 80% of the fuel used, e.g. natural gas, becomes heat in your home. The rest of the 20% is lost through the chimney or as waste.

So, every bit of fuel that is wasted equates to dollars every day–especially during those cold winters.

It’s worth checking your furnace’s efficiency rating by looking up the manufacturer, model and year of your furnace. If yours is recently installed, you may be able to ask the service who installed it for you.

Other Factors Affecting Your Comfort & Heating Bill

For those who like to learn mechanical details, here’s a good short video explaining how a home furnace works.

Here are a few more things I learned that can directly affect the warmth and heating bill of your home.

Thermostat Settings:  Of course, this might seem too obvious. Set the thermostat higher, and the house gets warmer. You may not be aware how responsive and how the thermostat responds matters, too. We ended up getting a smart thermostat, which made our home in the winter more comfortable and cut our heating bill by 10%. It adjusted our setting throughout the day automatically.

Leaks: This one might seem obvious again at first, but the magnitude of the problem is often underestimated. For example, leaving a window “cracked” open for a long time lets a lot of heat escape. Conversely, opening a door wide open “just for a few minutes” can blow a lot of that precious heat out. Then, there’s the pet door, which often surprises people how much, besides your pet, escapes through them.

Size of Furnace: Lastly, I learned that matching the size of your furnace to the size of your home and needs of your household can be quite important as well. According to this article, here’s a rough estimate of what furnace size is appropriate for what size home:

• 1,200 sq ft house: 36,000 to 72,000 BTUs
• 1,500 sq ft house: 45,000 to 90,000 BTUs
• 1,800 sq ft house: 54,000 to 108,000 BTUs
• 2,100 sq ft house: 63,000 to 126,000 BTUs
• 2,400 sq ft house: 72,000 to 144,000 BTUs

By the way, a BTU stands for British Thermal Unit. It’s a measurement of energy.