Geothermal Energy

Geothermal Energy Pros and Cons

Last updated June 1, 2013 by Mathias Aarre Maehlum


This article is well-researched and contains every aspect a balanced geothermal energy pros and cons list should contain.
Note that the list is based on the two main ways we harness geothermal energy today: Electricity generation with geothermal power plants and geothermal heating and cooling systems.

See more in-depth information further down the page. Here`s a short overview over the most important benefits and downsides:


Pros of Geothermal Energy

Geothermal energy is generally considered environmentally friendly and does not cause significant amounts of pollution.
Geothermal reservoirs are naturally replenished and therefore renewable (it is not possible to exhaust the resources).
Massive potential – upper estimates show a worldwide potential of 2 terawatts (TW).
Excellent for meeting the base load energy demand (as opposed to other renewables such as wind and solar).
Great for heating and cooling – even small households can benefit.
Harnessing geothermal energy does not involve any fuels, which means less cost fluctuations and stable electricity prices.
Small footprint on land – can be built partially underground.
Geothermal energy is available everywhere, although only some resources are profitably exploitable.
Recent technological advancements (e.g. enhanced geothermal systems) have made more resources exploitable and lowered costs.


Cons of Geothermal Energy

There are some minor environmental issues associated with geothermal power.
Geothermal power plants can in extreme cases cause earthquakes.
There are heavy upfront costs associated with both geothermal power plants and geothermal heating/cooling systems.
Very location specific (most resources are simply not cost-competitive).
Geothermal power is only sustainable (renewable) if the reservoirs are properly managed.


Advantages of Geothermal Energy

1. Environmentally Friendly

Geothermal energy is generally considered environmentally friendly. There are a few polluting aspects of harnessing geothermal energy (read more about them in the disadvantages section), but these are minor compared to the pollution associated with conventional fuel sources (e.g. coal, fossil fuels)

The carbon footprint of a geothermal power plant is minimal. Further development of our geothermal resources is considered helpful in the fight against global warming.
An average geothermal power plant releases the equivalent of 122 kg CO2 for every megawatt-hour (MWh) of electricity it generates – one eight of the carbon emissions associated with a typical coal power plant.


2. Renewable

Geothermal reservoirs come from natural resources and are naturally replenished. Geothermal energy is therefore a renewable energy source.

Sustainable is another label used for renewable sources of energy. In other words, geothermal energy is a resource that can sustain its own consumption rate – Unlike conventional energy sources such as coal and fossil fuels. According to scientists, the energy in our geothermal reservoirs will literally last billions of years.


3. Massive Potential

Worldwide energy consumption – about 15 terawatts (TW) – is not anywhere near the amount of energy stored in earth. However, most geothermal reservoirs are not profitable and we can only utilize a small portion of the total potential. Realistic estimates for the potential of geothermal power plants vary between 0.035 to 2 TW.
Geothermal power plants across the world currently deliver about 10,715 megawatts (MW) of electricity – far less than installed geothermal heating capacity (about 28,000 MW).


4. Stable

Geothermal energy is a reliable source of energy. We can predict the power output of a geothermal power plant with remarkable accuracy. This is not the case with solar and wind (where weather plays a huge part in power production). Geothermal power plants are therefore excellent for meeting the base load energy demand.

Geothermal power plants have a high capacity factor – actual power output is very close to total installed capacity.
The global average power output was 73% (capacity factor) of total installed capacity in 2005, but as much as 96% has been demonstrated.


5. Great for Heating and Cooling

We need water temperatures of more than 150°C (about 300°F) or greater in order to effectively turn turbines and generate electricity with geothermal energy.

Another approach is to use the (relatively small) temperature difference between the surface and a ground source. The earth is generally more resistant to seasonal temperature changes than air. Consequently, the ground only a couple of meters below the surface can act as a heat sink/source with a geothermal heat pump (much in the same way an electrical heat pump works).

We`ve seen a tremendous growth in the number of homeowners that utilize geothermal heating/cooling in the last couple of years.


Disadvantages of Geothermal Energy

1. Environmental Issues

There is an abundance of greenhouse gases below the surface of the earth, some of which mitigates towards the surface and into the atmosphere. These emissions tend to be higher near geothermal power plants.

Geothermal power plants are associated with sulfur dioxide and silica emissions, and the reservoirs can contain traces of toxic heavy metals including mercury, arsenic and boron.

Regardless of how we look at it, the pollution associated with geothermal power is nowhere near what we see with coal power and fossil fuels.


2. Surface Instability (Earthquakes)

Construction of geothermal power plants can affect the stability of land. In fact, geothermal power plants have lead to subsidence (motion of theearth’s surface) in both Germany and New Zealand.

Earthquakes can be triggered due to hydraulic fracturing, which is an intrinsic part of developing enhanced geothermal system (EGS) power plants.
Just a couple of years ago (January 1997), the construction of a geothermal power plant in Switzerland triggered an earthquake with a magnitude of 3.4 on the Richter scale.


3. Expensive

Commercial geothermal power projects are expensive. The exploration and drilling of new reservoirs come with a steep price tag (typically half the costs). Total costs usually end up somewhere between $2 – 7 million for a geothermal power plant with a capacity of 1 megawatt (MW).

As previously mentioned, most geothermal resources cannot be utilized in a cost-effective manner, at least not with current technology, level of subsidies and energy prices.

The upfront costs of geothermal heating and cooling systems are also steep. On the other hand, these systems are likely to save you money years down the line, and should therefore be regarded as long-term investments. Ground source heat pumps typically costs $3,000 – $10,000 and have a payback time of 10 – 20 years.


4. Location Specific

Good geothermal reservoirs are hard to come by. Some countries have been blessed with great resources – Iceland and Philippines meets nearly one third of their electricity demand with geothermal energy.

If geothermal energy is transported long distances by the means of hot water (not electricity), significant energy losses has to be taken into account.


5. Sustainability Issues

Rainwater seeps through the earth’s surface and into the geothermal reservoirs over thousands of years. Studies show that the reservoirs can be depleted if the fluid is removed faster than replaced. Efforts can be made to inject fluid back into the geothermal reservoir after the thermal energy has been utilized (the turbine has generated electricity).

Geothermal power is sustainable if reservoirs are properly managed. This is not an issue for residential geothermal heating and cooling, where geothermal energy is being used differently than in geothermal power plants.



The bottom line is this: Geothermal energy is generally regarded as environmentally friendly, sustainable and reliable. This makes geothermal energy a no-brainer in some places, but heavy upfront costs stops us from realizing the full potential.

How much influence geothermal power will have on our energy systems in the future depends on technological advancements, energy prices and politics (subsidies). No one really knows what the situation will look one or two decades down the line.

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