Energy efficiency is a hot topic (pun intended) today. We get calls every day from customers asking about which furnace brand or fuel type will deliver the most heat for the lowest price.
But energy efficiency has as much to do with the space being heated, the type of fuel used, seasonal weather and other variables as it does with the HVAC equipment you choose.
In this article, we get up close and personal with variables impacting energy efficiency, explaining what you need to know to save the most on heating this winter.
Energy Efficiency Variables
While it is accurate to say that some types of heating equipment are naturally more energy efficient than others, this is far from the only factor that can influence how much it costs to heat your space.
A number of other variables can also impact how much heat you get out of your furnace and how much energy you have to buy to get it. Minimizing the impact of each of these variables is one key to maximizing the energy efficiency of your heating equipment.
Traditional furnaces are considered “heat only” equipment. They operate on a model of cold start-up, which means they power on from an unheated state and instantly begin generating heat.
While this concept is more critical for energy efficiency in equipment that heats water (radiant heater, boiler, etc.), it still contributes to inefficient fuel use at the start of a new heating cycle.
Incomplete combustion is a term used to describe poor fuel burning.
Incomplete combustion is often caused by poor furnace maintenance. Clogged furnace filters, dirt and dust in the internal mechanisms, worn components that have not been lubricated and other factors can lead to incomplete combustion.
The most dangerous aspect of incomplete combustion is an increase in carbon monoxide off-gassing. A side effect is reduced energy efficiency and higher heating bills.
Heat loss through the chimney
If your home has a fireplace with a chimney, the chimney can act as a conduit to allow warmed air to escape from your home and force your furnace to work harder to keep your space heated.
Heat loss through cracks and leaks
Lack of proper or adequate insulation can lessen energy efficiency by forcing the furnace to work harder to keep your space warm.
Caulking, weather stripping, insulating and draft-proofing can all boost energy efficiency by cutting off the escape routes of warm indoor air.
Heat losses due to combustion gases
As Natural Resources Canada explains it, along with combustion comes some inherent risk of transient heat loss.
While the full explanation is somewhat complex, essentially some heat is carried away when the furnace pushes extra air through to ensure the most complete and safe fuel combustion.
Different Measures for Energy Efficiency
Each of these terms analyzes heating energy efficiency from a different and important perspective.
Steady state efficiency
Because most heating equipment operates in cold-start mode, it can take some time for your furnace to reach its optimal operational temperature.
Steady state efficiency is a measure of how efficiently your furnace burns fuel to heat your space once it has reached its optimal temperature.
Most homeowners are more familiar with the term “annual fuel utilization efficiency” (AFUE), which is another way to say seasonal efficiency.
For example, if an appliance is rated at 80 percent AFUE, this means that 80 percent of the fuel the unit draws will be used to generate heat. The remaining 20 percent will be lost, either up the chimney, out through unsealed cracks or leaky ducts, or in similar ways.
Seasonal efficiency is also a measure of how well furnace equipment will heat a space given changing air temperature, heat loss between furnace cycles and efficiency losses when the furnace is warming up at the start of a new cycle.
Design heat load
The word “load” indicates how much heating your space requires (the size of your space as well as the ambient seasonal winter outdoor temperature).
Design heat load, then, refers to how hard your furnace will have to work to heat your space to the desired temperature. This also factors in heater capacity, which is a measure of how much heat a furnace unit is able to provide.
Closely matching the heat load and the heat capacity will result in the most energy efficient heating operation.
Impact of Fuel Type on Energy Efficiency
Where you live can have an impact on what fuel options are available to you. Common options include electricity, natural gas, propane, oil and wood. Air, water and geothermal options can also be harnessed to operate heat pump equipment.
Some fuel types are naturally more energy efficient. But here, it is also important to balance energy efficiency against fuel and installation costs.
For example, air-source heat pumps or geothermal heat pumps may use the most efficient fuel type, but they can also come with a higher installation price tag and may take longer to pay for themselves.
Impact of Heat Distribution Method on Energy Efficiency
Finally, the method by which heat is distributed throughout your space can have a direct impact on energy efficiency.
Traditional radiators can be inherently less efficient due to steam loss.
Of the two, forced-air furnace systems are generally considered more energy efficient as long as the ductwork is well-maintained and free from cracks or leaks.
However, some modern radiant heating systems can also be very efficient.
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Want to learn more about how to save money on heating costs as the winter season continues? Ready to schedule your mid-winter furnace preventative maintenance service?