Alberta’s heating infrastructure relies heavily on natural gas, with most homes equipped with gas-fired furnaces. However, the environmental impact, economic constraints, and finite availability of natural gas have led to a growing interest in alternative heating options. Our family’s interest peaked as our 1980s natural gas furnace seized for good during the last cold snap of February 2023, prioritizing and expediting our research into finding a suitable replacement.
In Alberta, natural gas has traditionally been the predominant heating source for homes thanks to our wealth of natural resources like oil and our skilled and talented workforce that can extract it. The easy accessibility and affordability of natural gas have made it the default choice despite its significant carbon footprint. The province’s energy grid was designed primarily for natural gas because electricity from sustainable and economical sources like hydroelectricity is less widely available than in Canadian provinces like B.C. and Ontario. This dual approach to our utility grid means that most homes are equipped with a smaller electrical service entrance (typically 100 amp vs 200 amp service) to meet the demands of our lights and appliances, and then natural gas supplies the means to power our furnaces, hot water tanks and sometimes even dryers and ranges.
Challenges with Gas-Fired Furnaces
Natural gas has a combustion temperature of 1690°C. However, their efficiency is compromised due to energy wastage through exhaust and combustion. While natural gas can generate considerable heat, not everything is utilized to warm the home. Moreover, relying on natural gas for space heating limits our supply to export for economic gain or utilization in other sectors dependent on it, such as manufacturing or commercial transportation.
Heat pumps offer an effective alternative to gas-fired furnaces for home heating. Geothermal and air source heat pump systems leverage existing heat sources to provide warmth efficiently. Unlike gas-fired furnaces, heat pumps do not rely on combustion; they transfer heat from lower temperature sources like the air or ground.
Heat pumps, whether geothermal or air source, operate on the principle of exergy – the valuable energy that can effectively provide heat or perform work. Rather than generating heat from scratch, they extract heat from the outdoor environment. This starting temperature is typically lower than what a gas-fired furnace requires. As a result, heat pumps require less energy and effort to achieve the desired indoor temperature, making them more efficient and environmentally friendly.
When comparing these starting temperatures, we look at how Gas-fired furnaces burn natural gas that has a relatively high combustion temperature to heat a home to a comfortable temperature that we are used to. In contrast, air source heat pumps only need to adjust the starting temperature, which may come from the air or ground temperatures. The difference between an average outdoor winter temperature of, say -8°C to the target temperature on your home’s thermostat of, say, 22°C has a variance of only 30 degrees as opposed to a natural gas combustion temperature of 1690°C which has a variance of 1668 degrees. I think it feels wasteful of an overpowered heat energy source that is better used elsewhere.
Constraints and limitations of Alberta’s weather
In Calgary, the average winter outdoor temperatures range from around -8 to -2 °C, with January typically being the coldest month, where temperatures can occasionally drop below -20 °C or -30°C and beyond. During the summer, average temperatures in Calgary range from around 15 to 24 °C. These temperature ranges help frame the context for considering regional heating options.
Although the average temperatures in Alberta are well within most heat pump capabilities, it’s the extreme temperatures that are cause for concern. In regions like Alberta and our northern neighbours that observe frigid temperatures, it is expected or even necessary to have a backup or secondary heating system installed alongside air-source heat pumps. While “cold climate air source heat pumps” are designed to work in lower temperatures and can operate down to -25 degrees Celsius, there are times when extreme weather conditions can surpass an air source heat pump’s effective range for more extended periods. For example, the top 20 lowest recorded temperatures in Calgary’s history over the last 143 years have all been below -40 °C.
Heat Pump Choices
To ensure adequate heating during extreme cold days or situations in which the heat pump cannot meet the home’s heating demands, having a secondary heating source becomes essential. This may include options such as a furnace, electric resistance heating, or another heating system providing sufficient heat when needed.
Alternatively, while air-source heat pumps may struggle or falter in icy air conditions, geothermal heat pumps offer an attractive alternative solution where installation is feasible. Geothermal systems take advantage of the more stable ground temperatures available below the frost line. Ground temperatures typically range from 6 to 8 degrees Celsius in my region.
Geothermal heat pumps extract heat from the ground through a process similar to your kitchen’s refrigerator. Using the stable ground temperature as a heat source allows for reliable operation and consistent heating, even during extreme cold weather. Additionally, geothermal heat pumps can provide cooling by transferring heat from the warm indoor air back into the cooler ground, which essentially recharges the heat energy in the ground in addition to the daily amount of energy absorbed by the earth from the sun. So, in overly simplified terms, we are using the ground as a heat energy battery or savings account, depositing heat energy or saving it in the summer months and withdrawing it in the winter.
Choosing the right heating system for your home can be a daunting task, and a lot depends on the weather conditions and the specific needs of your household. Ultimately, choosing between gas-fired furnaces, air-source heat pumps, or geothermal systems depends on climate, energy efficiency goals, and individual preferences. Consultation with HVAC professionals, Certified Energy Auditors, or Building scientists to assist in considering the specific requirements of your home will help determine the most suitable heating option based on your individual home’s needs.
In our case, we decided to go with geothermal heat exchange as our primary replacement for our 40-year-old natural gas furnace. This was primarily because of the science of thermodynamics and meteorology and the constraints of physics with our small electrical entrance, which made us believe that geothermal heat exchange was the best option for us.
While we love air-source heat pumps, we realized they might not be the best option for our home’s heating needs. We needed to be sure that the heating system we chose would work efficiently, no matter what the temperature was outside, to keep our children warm and comfortable at night reliably.
On the other hand, we use a ductless mini-split air source heat pump to heat our detached garage. Since the garage is not inhabited all the time, we felt confident in choosing air-source heat pumps and making a lifestyle choice to avoid working on our automotive or woodworking hobbies when the temperature outside is beyond the air-source heat pumps’ capabilities.
Remembering that the right tool for the right job is essential when choosing a heating system. Suppose we lived somewhere else with different weather conditions or in a new Passive certified home that is highly insulated. In that case, we might have made another choice, no matter how much we are enjoying our new heating system.
As Alberta continues to explore sustainable energy solutions, adopting more efficient heating systems can reduce carbon footprints to meet our climate change goal and preserve valuable resources for other sectors where fossil fuels are irreplaceable.