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New research: Comparing residential heating systems

How do you choose the right heating system for your project? A new analysis shows that client and project goals really matter.

Every home heating system has trade-offs. That’s what makes a great heating contractor or mechanical engineer so valuable: They can help weigh the pros and cons of different systems and come up with the best solution for a given home.

A new analysis and training course from engineering consultants Newport Partners LLC make that job a little easier. In “A Comparative Analysis of Residential Heating Systems,” Newport Partners examined the performance of seven heating systems across 16 different locations in the United States in terms of their first cost, energy cost, emissions simple payback, and, in some cases, comfort. (To learn more about the study’s methodology and see the full results, check out the course or the executive summary.)

The research, says senior consultant Jamie Lyons, shows that the priority of those objectives really matters when it comes to choosing the right heating solution.

“Your objectives can range from the first cost of the heating system to the annual energy cost,” he says. “You can do a combination of those: What’s the lifecycle cost? There can be emissions considerations for some folks; there can be comfort considerations. So, whether you’re a builder, a remodeler, or a homeowner, it’s important to start with ‘What are the objectives that matter most for this project?’ and then assess the possibilities through that lens.”

Here are some of the factors that might be important on your next project, along with details on how the heating systems performed.

First costs

HeatingStudy_FirstCosts

Upfront costs are an important factor for just about any project. The chart above shows the average first cost of each system across all 16 locations for new homes. First costs include the equipment and installation costs, the costs of the duct system, and the first cost of the cooling system — so there is an even comparison between furnaces, which only provide heat, and heat pump systems that perform both functions.

The lowest-first-cost systems are common options: a standard-efficiency propane furnace with standard A/C (system A), the high-efficiency propane furnace with standard A/C (system B), and a standard-efficiency air source heat pump (system F). These systems have first costs within about 3 percent of each other — all right around $11,000. The standard- and high-efficiency propane furnaces end up with comparable first costs because the venting is less expensive for the high-efficiency furnace, even though the equipment is more expensive.

The much higher first cost of the ground source heat pump (GSHP, system D) is driven significantly by the cost of the ground loop drilling and materials.

Energy costs

HeatingStudy_EnergyCosts

Of course, upfront costs aren’t the only financial factor in the decision. The ongoing cost to operate the heating system affects the long-term cost. In this chart, the energy costs to provide space heating and cooling to the prototype house are shown as annual estimates for new homes in the cold climate zone.

The analysis showed that the high-efficiency propane furnace (system B) has about 10 percent lower annual energy costs compared to the standard air source heat pump (system F) and about 14 percent lower annual energy costs compared to the heating oil furnace (system C). Given its reasonable first costs and expected comfort advantages (discussed below), the high-efficiency propane furnace would be a solution that meets multiple project needs in cold climates.

Lyons notes that one interesting nuance of the study is that today’s new homes are more efficient compared with homes built to code six or 10 years ago. Current energy codes require greater levels of insulation and are more stringent with air sealing. “You’re just running the heating system less,” he says. “So if you invest a lot of additional money up front in a high-performance system like a ground source heat pump, it’s going to take longer to get that payback just because the heating system is operating less.”

So, while the GSHP and the GSHP-propane furnace hybrid system offer the lowest annual energy costs, simple payback scenarios (shown below) show that the higher upfront cost of those systems can take 20 or more years to recover in the form of energy savings for a new home. “Especially for new homes, the high-efficiency propane furnace sure offers a good value,” Lyons says. “It has a small cost premium compared to a standard furnace but provides energy savings.”

HeatingStudy_Scenario-A

Comfort

For many homeowners, comfort is a deciding factor when selecting a new system or deciding between repairs and replacement. The reputation of heating systems for providing comfort varies greatly, with systems such as propane forced-air furnaces often expected to provide greater comfort than air source heat pumps, especially in cold climates. The Newport Partners study used modeling data to help quantify the expected comfort of the heating systems in the study.

HeatingStudy_Comfort

The results, Lyons says, support the perception that propane heating systems are more comfortable than heat pumps. The study used building energy simulation tools to project the heating supply temperatures of forced-air systems. Supply temperatures at or below typical body temperature (approximated as less than or equal to 100 degrees Fahrenheit) were assumed to feel cool and be uncomfortable.

The simulations show that the air source heat pump, shown in blue on the chart, supplies air varying in temperature from 90 to 115 degrees, even when the air source heat pump’s backup electric resistance heating element is taken into account. In this cold climate, the supply air from the heat pump feels “cool” a large percentage of the heating season. The propane furnace, by contrast, consistently delivers air at 115 degrees or higher, as shown in red.

Emissions

HeatingStudy_Emissions

If carbon emissions are a key consideration for your project, the location of your project matters. That’s because while heating systems fueled by propane, heating oil, or natural gas release greenhouse gasses (GHGs) such as CO2 as a result of the combustion of the fuel, electricity-based heating systems also result in carbon emissions that are sometimes greater than a fossil fuel heating system like a furnace. A large portion of electricity in the United States is produced from power plants that rely on fossil fuels to create thermal energy, which is then converted to electrical energy.

“In regions like the Midwest, air source heat pumps can still have pretty high emissions rates, and it’s driven by two factors,” Lyons says. “The power generation mix — how the electric power is being generated — and then the use of the heat pump’s electric resistance backup heat.”

The chart above shows the CO2 emissions resulting from operation of the heating systems averaged across the seven Midwest analysis locations. The chart shows that the standard-efficiency air source heat pump (system F) results in significantly higher emissions than all other systems, including the propane furnaces, the heat pump-furnace hybrid, and the ground source heat pump systems. The difference between the high-efficiency propane furnace (system B) and the air source heat pump is about 2.1 metric tons of CO2 emissions. Over the 15-year life of these systems, the total difference in emissions would be like the total emissions from a passenger car over about seven years.

Calculate your own scenarios

Your project’s location, size, efficiency, and energy costs affect not just the emissions calculations but the cost calculations as well, so there’s no heating system that’s perfect for every project. But with our Space Heating Energy Calculator, you can input data specific to your project to calculate costs and emissions, then compare it to a second system to see how your home’s efficiency and expenses can improve.

Check out “A Comparative Analysis of Residential Heating Systems” in the Propane Training Academy for an in-depth review of the study, and earn learning credits from the American Institute of Architects Continuing Education System and the Green Business Certification Institute.

Published November 13, 2018

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