(Almost) Everything You Need to Know About Geothermal Energy

As we increasingly try to use the earth’s heat to decarbonize buildings (among other things), benefits and barriers are under discussion.
July 8, 2024

Geothermal energy is, simply, harnessing the power of the heat from inside the earth. This form of energy is now gaining more and more attention locally, mostly because a giant underground geothermal heat pump is being built at 1 Java Street in New York. As we increasingly try to use the earth’s heat to decarbonize buildings (among other things), benefits and barriers are under discussion.

What is geothermal energy?

The word geothermal comes from the Greek words geo (earth) and therme (heat). Geothermal energy refers to the production of energy using the internal heat of the Earth’s crust.  

Although many of us experience seasonal temperature changes, a few feet below the earth's surface the ground remains at a relatively constant temperature. This ground temperature is warmer than the air above it during the winter and cooler in the summer. To produce geothermal energy at an industrial level, wells are drilled into the Earth’s crust at a depth of approximately 2 – 6 miles and extract the heat using water and steam.

What are geothermal heat pumps?

Geothermal Heat Pumps (GHPs) have been in use since the late 1940s. They can heat, cool, and supply a building with hot water. GHPs can transfer heat stored within the Earth into a building during the winter, and transfer heat out of the building into the Earth during the summer.  Some houses in the NYC area use GHP systems to both heat and cool by putting a pipe about 5 feet deep in the ground and circulating water.

In recent years, buildings have been a major source of the city’s carbon emissions. In New York City, 1 million existing buildings generate 70 percent of the city’s annual carbon emissions, primarily by burning fossil fuels for heating, cooling and lighting.

To decarbonize climate control in buildings, GHP projects have been applied to many buildings in the US. According to the U.S. Environmental Protection Agency (EPA), geothermal heat pumps are the most energy-efficient, environmentally clean, and cost-effective systems for heating and cooling buildings. For now, around 50,000 geothermal heat pumps are installed in the US per year.

Why are GHPs good?

Relative to air-source heat pumps, GHPs are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.

Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings.  

What are the concerns?

Geothermal heat pumps can be expensive to install because the soil needs to be dug up to install the connecting pipe. According to Forbes, for a geothermal heating and cooling system, the average cost is $24,500.

Additionally, local geological conditions can affect the cost and performance of a GHP system. This means that the installation process may be more complex and expensive due to the state's varied geological landscape. A New Yorker may also think of the costs of maintenance and repairs, space constraints and seasonal performance variability before they decide to install a GHP.

GHPs present an important solution for sustainable heating and cooling. As New York continues to explore sustainable solutions for reducing carbon emissions, geothermal energy stands out as a promising option. For New Yorkers, before going for a GHP system, it’s crucial to carefully think about the costs and expenses, as well as the potential long-term savings and environmental impact.  

No one solution will fix everything, but GHPs are 1 piece of the puzzle.