What are the Differences Between Furnaces, Boilers, and Stoves?

Thermodynamically, furnaces, boilers, and stoves have similar functionalities. Here’s a quick overview:

Furnaces heat air, utilizing an air handler to distribute the warm air through ductwork.

Boilers heat water, circulating it through pipes to radiators that warm the rooms.

Stoves serve as central heat sources, often featuring fans but limited in their heat distribution capabilities.

Although each type has its advantages and disadvantages, cost and emissions are largely comparable. The efficiency varies, but differences are typically within the 10-20% range. I’ll refer to these heating methods collectively as “traditional heat.”

What Makes Electric Heaters Unique?

Crucially, electricity is the only heat source that can be emissions-free.

Traditional combustion heaters rely on burning fuels (such as natural gas, propane, or wood) on-site to generate heat. This process can lead to inefficiencies and health risks due to incomplete combustion, necessitating the expulsion of exhaust outside the home.

Electric heating is already commonplace in various appliances: toasters, electric ovens, space heaters, and more. An electric heater operates on similar principles, scaled up for home use.

Conventional electric heaters employ resistive heating, where an electrical current passes through a resistor to produce heat.

These resistive heaters boast 100% efficiency and do not require exhaust systems. Their versatility and simplicity make them a frequent choice for affordable housing.

Will Switching to Resistive Heat Save Money or Help the Environment?

Unfortunately, the answer is no. Currently, traditional electric heaters are generally more expensive and often contribute to a larger carbon footprint.

Most electricity still comes from fossil fuel sources. This means that an electric boiler may still be indirectly powered by methane, just like a gas boiler. The process of converting methane to electricity at power plants is only about 40% efficient, which escalates both costs and emissions.

While electric heating has the potential to be emission-free, achieving this requires additional steps on your part. Depending on your location and energy payment plan, your electricity could already be significantly cleaner than indicated in the graph above.

The grid is gradually improving, with various initiatives aimed at decarbonization. Installing rooftop solar panels can provide your own clean energy, and you may have options for zero-emissions energy sources that are cheaper than conventional electricity. This was my experience.

Transitioning to a completely emission-free electric grid is complex. As environmentally aware consumers, our role is to promote electrification, but we also need utility companies and regulatory bodies to shift towards cleaner electricity sources.

Natural gas currently stands as the most affordable and cleanest widely used heating source. However, it poses storage risks due to its explosive nature, limiting its use to specific locations and demographics.

Regardless of your choice of fuel, traditional electric heating tends to come with higher costs in most homes.

Can Heat Pumps Provide More Than 100% Efficiency?

Surprisingly, yes! Heat pumps (HP) offer an efficient alternative. Rather than generating heat, they transfer it from outside to indoors. Under optimal conditions, an efficient heat pump can move 3 kWh of heat into a home using only 1 kWh of electricity.

The technology behind heat pumps is akin to that of refrigerators and air conditioners. Essentially, a heat pump functions as an air conditioner that can also provide heating. If you can install an air conditioning unit, you can install a heat pump as they share the same technology.

Can a Heat Pump Replace a Furnace?

The two systems are not directly interchangeable. A more effective approach to heating your home can lead to savings and reduced emissions.

The efficiency of heat pumps varies due to multiple factors. Some are within your control (indoor temperature, equipment efficiency), while others are not (outdoor temperature, humidity), and some aspects are challenging to modify (home size, duct dimensions).

Every home has its own unique characteristics. I can’t predict how well a heat pump will perform in your situation. Some users have reported successful operation down to 5°F (-15°C), while my heat pump struggles below 25°F (-4°C). In such cases, I rely on a backup furnace in a dual-source configuration.

A dual-source system may seem complex, but it closely resembles a setup that includes both air conditioning and a traditional heating method. Use the heat pump for cooling in summer and moderate heating in winter, then switch to the traditional system for extreme cold spells. Any smart thermostat can accommodate dual-source heating.

Comparing heat pumps to traditional heating methods comes with caveats. I have extensive data from my own home, but your results may vary.

How Do Heat Pumps Compare to Traditional Heating Costs?

Heat pumps perform well in mild temperatures and remain effective as it gets colder, although they struggle in extreme conditions. The graph indicates the temperatures at which my home loses more heat than the heat pump can supply, necessitating the use of a traditional heater.

Even at lower efficiency, heat pumps outperform all other fuel sources in terms of emissions. However, during extremely cold conditions, gas furnaces and wood may be more economical.

What Is the Cost of Efficient, Emission-Free Heating?

In my case, I utilize clean electricity and maintain a dual-source system. Hence, my only carbon emissions come from the gas furnace during colder periods.

Last year, my heat pump accounted for approximately 60% of my heating needs, resulting in a reduction of over a ton of emissions compared to relying solely on gas and lowering my heating expenses by about $100.

It took years of careful monitoring to accurately assess the cost-effectiveness of gas versus a dual-source system. While a heat pump is likely to save you money, the benefits may not be immediately apparent from your bills.

I continue to refine my thermostat settings and anticipate that my furnace will contribute less than 20% of my heating in the upcoming season. Stay tuned for a follow-up article in spring with more data.

To achieve zero emissions, I would need to replace my furnace with a resistive heater, which would raise costs.

With my current configuration, costs could nearly double. I could potentially lower the heat pump lock-out temperature to 25°F (-4°C), but fully transitioning to electric heating would still result in an increase of about $200 annually.

Is It the Right Moment to Transition to All-Electric Heating?

For the time being, I will continue using my gas furnace, which still has over ten years of service left. While I rely on it less often now that I have a heat pump, it remains necessary.

However, many of us can take steps toward partial electrification to save money. If you plan to replace or install a new air conditioning unit, consider opting for a heat pump instead; the benefits far outweigh the disadvantages. Subsidies and savings on heating costs can counterbalance the higher installation expenses. Many households may discover they can rely solely on a heat pump for heating.

In cases like mine, where the heat pump is inadequate during the coldest periods, an all-electric system remains challenging. If the increased costs are a concern, widespread adoption may be limited.

Resistive heating may still be beneficial in specific circumstances:

• For individuals wholly committed to zero-emissions lifestyles.
• For homes with excess rooftop solar or other free clean energy sources.
• For oil or propane users, slightly higher expenses might be a reasonable trade-off for significantly reduced emissions.

For most, home heating will largely transition to electricity, reducing emissions but not eliminating them.

The higher costs of electricity remain a significant barrier. As we build infrastructure to clean the grid, it’s likely the cost per kWh will rise to fund this transition. While a carbon tax on heating fuels may seem like a solution, affordability is essential for many, including myself.

Nevertheless, if we are serious about reducing emissions, we must work on cleaning the electricity supply and finding ways to make electric heating costs competitive with high-carbon alternatives.