What Is A Disadvantage Of Geothermal Heat Pumps?

High Upfront Cost

One of the biggest disadvantages of geothermal heat pumps is the high upfront cost compared to traditional HVAC systems. According to Modernize, a reputable home improvement site, just the heat pump unit alone costs $2,500 to $5,000, and installing the full geothermal system can range from $15,000 to $38,000 for a 2,000 square foot home [1]. Angi, another home services marketplace, reports an average cost of around $15,075 for a complete geothermal installation, with costs ranging from $800 for a small 1-ton unit up to over $50,000 for larger systems [2]. This is significantly more expensive than installing a traditional gas furnace or air conditioner.

Limited Applications

One disadvantage of geothermal heat pumps is their limited applications. Geothermal heat pump systems require sufficient land area to install the ground loop piping, which makes them only feasible for heating and cooling buildings with adequate outdoor space such as single-family homes, schools, and commercial buildings. The large land area needed for horizontal loops or vertical boreholes prevents geothermal heat pumps from being installed in homes without yards or multi-family buildings like apartment complexes. While a lake or pond loop is an option for some properties, the availability of a suitable body of water nearby also limits where geothermal systems can be utilized. The amount of land space required is a major limiting factor, restricting geothermal heat pumps to certain building types and locations.

Installation Challenges

Installing a geothermal heat pump system can present significant challenges that increase costs and complexity compared to other HVAC systems. Geothermal systems require drilling boreholes deep underground to install the ground loops that harness the earth’s natural warmth. This necessitates specialized drilling equipment and expertise to ensure proper loop installation. According to Energysage, “Specialized drilling rigs are used to drill holes ranging from 150 to 600 feet deep in the ground to install vertical loops for a ground source heat pump system.” ¹ The drilling process is complex, with many factors to consider such as soil conditions, underground obstructions, and optimal loop depth and configuration.

In addition to the ground loops, the heat pump and distribution system (ductwork or radiant tubing) must be properly designed, sized and integrated for optimal performance and efficiency. Improper installation can lead to system imbalance, short cycling, and premature component failure. Hiring qualified geothermal contractors is highly recommended, as they have the expertise to handle all aspects of installation. The specialty equipment, expertise and labor involved in installing geothermal systems make the process more challenging compared to standard HVAC systems.

Unsuitable Geography

One major disadvantage of geothermal heat pumps is that they require specific geological conditions to operate efficiently. As explained by Fervo Energy, “This traditional approach has significant geographic limitations. Hydrothermal resources occur in very few places where you find the combination of heat, permeability and fluid that make them viable.” https://fervoenergy.com/geothermal-myth-2-geothermal-is-geographically-constrained/

In particular, geothermal heat pumps need access to subsurface rock or soil with appropriate temperatures. As discussed in a Frontiers in Energy Research paper, “A shallow geothermal resource exists both below the surface (generally less than 200 m depth) within a certain range of rock mass, groundwater, or soil types that are suitable for economic exploitation.” https://www.frontiersin.org/articles/10.3389/fenrg.2022.928125

Areas without those subsurface temperature conditions cannot effectively utilize geothermal heating and cooling systems. As Power Grid notes, “The system must be located over suitable geological formations that have specific thermodynamic features such as moderate earth temperature gradients.” https://www.power-grid.com/energy-efficiency/geothermal-district-heat-pumps-an-efficient-way-for-smart-cities-to-decarbonize/

Long Payback Period

One disadvantage of geothermal heat pumps is the long payback period. According to the Department of Energy, geothermal heat pumps have a payback period between 5-10 years [1]. This means it can take over a decade to recoup the high upfront costs through energy savings [2]. One analysis found the payback period to be just under 10 years if annual energy savings were $1,617 and annual hot water and maintenance savings were $1,000 [3]. The long payback period makes geothermal heat pumps a significant investment. While they can save money over time, the upfront cost and time to recoup that investment can be prohibitive for some homeowners.

Maintenance Requirements

Like any HVAC system, geothermal heat pumps require some periodic maintenance to keep operating efficiently. Typical maintenance includes checking refrigerant levels, inspecting air filters, cleaning coils, and lubricating fans once or twice a year. The underground loop system should be checked for leaks and re-pressurized if needed. Valves, pumps, and controls should be tested. Proper water quality must be maintained in the loop to prevent corrosion. While competent DIYers can handle some maintenance, complex repairs require specialized expertise. According to HomeAdvisor, the average cost of geothermal repair is $174 to $1,332, with some jobs costing over $4,000 for major issues. Preventative maintenance helps minimize repairs and extends the system’s service life.

Source: HomeAdvisor

Noise Pollution

One potential disadvantage of geothermal heat pumps is that the outdoor units can generate noise that disturbs neighbors. The units contain large fans and compressors that circulate refrigerant through the system. This equipment often produces a humming or whirring sound as it operates.

While manufacturers have worked to make modern geothermal systems quieter, the outdoor units still generate 50-60 decibels of noise. That’s similar to the amount of noise from a typical conversation. For nearby homes, this can be an annoyance, especially at night when ambient noise levels are lower.

Installing noise barriers around the outdoor unit can help mitigate noise pollution. Barriers made of sound-absorbing materials like acoustic foam panels help dampen the operational noise. Proper placement and landscaping can also direct noise away from neighboring properties. Nonetheless, the noise remains one of the top nuisance complaints related to geothermal heat pump systems.

Non-Renewable Backup

While geothermal heat pumps utilize the stable temperatures underground to provide heating and cooling, they still often require a secondary, non-renewable energy source as a backup system. This is because geothermal heat pumps are not always able to meet peak heating or cooling demands, particularly in extremely cold or hot weather. The most common backup system is electricity from the grid, which could come from fossil fuel power plants. Some geothermal heat pump systems also use natural gas, propane, or fuel oil as a supplemental heat source when needed. This means that despite tapping into a renewable resource in the form of the Earth’s natural heat, geothermal systems are not always 100% renewable since they rely on non-renewable energy sources for backup. Homeowners should factor in the potential need for non-renewable backup power when considering the benefits and drawbacks of a geothermal heat pump.

Environmental Impact

While geothermal energy is considered a clean and renewable energy source overall, some aspects of geothermal systems can negatively impact the environment if not managed properly. One potential issue is the drilling of wells to install the ground loops for geothermal heat pumps. Drilling can disrupt land and release greenhouse gases trapped underground according to the U.S. Energy Information Administration (https://www.eia.gov/energyexplained/geothermal/geothermal-energy-and-the-environment.php). Proper well drilling techniques and sealing procedures need to be followed to minimize any emissions released.

Another concern is the use of antifreeze in closed-loop geothermal systems. Ethylene glycol is typically used as an antifreeze to allow the systems to operate efficiently in cold weather. If leaks occur in the piping, this antifreeze can contaminate groundwater supplies according to research published in Frontiers in Built Environment (https://www.frontiersin.org/articles/10.3389/fbuil.2022.914227). Proper installation and maintenance is critical to prevent antifreeze leaks and reduce this environmental risk.

Aesthetic Disruption

One downside of geothermal heat pumps is that they can create aesthetic issues in yards or landscapes where they are installed. The installation process itself often disturbs lawns, gardens, and landscaping. Large equipment needs to be brought onsite, trenches dug, and pipes buried underground – all of which can damage existing plants, trees, and carefully designed landscapes.

In addition, the actual heat pump unit is visible above ground, usually located alongside the home. Some homeowners find these units unattractive and feel they detract from their home’s curb appeal. While covers or strategic placement can minimize visibility, many dislike having mechanical equipment clearly visible in their yard.

Compared to concealed HVAC systems or gas furnaces located entirely inside the home, the external components of a geothermal system are seen by some as an aesthetic downside. Those wanting an untouched landscape or seamless home exterior might view the pumps as an eyesore.

However, technology improvements and creative landscaping can help blend geothermal systems into the surroundings more naturally. And many homeowners find this a worthwhile tradeoff for the efficiency and cost savings geothermal heating and cooling provides.