Iceland Geothermal Energy: Three Different Numbers, and What Each One Actually Measures

Ask how much of Iceland's energy is geothermal and you can get three different answers: 29%, 90%, or 70%. All three are real. They measure three different things — electricity generation, home heating, and total primary energy — and once the label drops off, any of them reads as "Iceland's energy." Take the biggest one as an electricity share and you have Iceland's grid backwards: hydroelectric dams generate more than twice as much of its electricity as geothermal plants do.

This page keeps the three measurements separate and labels every figure with which one it is. The numbers come from Orkustofnun (the Icelandic National Energy Authority, which collected the country's energy statistics until it closed at the end of 2024) and a 2023 Iceland GeoSurvey (ÍSOR) presentation.

Three Different Numbers, Three Different Questions

Each of the three headline figures answers a different question:

The three shares diverge because they count different things. Electricity is only one use of energy; Iceland also uses geothermal heat directly — piping hot water into radiators and taps — and that direct heat never passes through a turbine, so it never shows up in electricity statistics. Total primary energy counts both, plus the oil in cars, boats, and planes. Mix the categories and you get sentences that sound right and are wrong, like "geothermal generates 70% of Iceland's power." It doesn't. Hydro does most of that.

If the underlying technology is new to you, our plain-English guide to what geothermal energy is covers the fundamentals; this article is about getting Iceland's specific numbers right.

Electricity: Hydro Leads, Geothermal Is Second

The generation summary on Orkustofnun's homepage lists three sources. (The agency's fuller annual tables also carry a small fuel-combustion category, far too small to move these percentages.) The site writes the figures Icelandic-style, with periods as thousands separators — "14.195 GWh" means 14,195 gigawatt-hours:

• Hydro: 14,195 GWh
• Geothermal: 5,916 GWh
• Wind: 5 GWh

Total those and you get 20,116 GWh. Divide it out: geothermal is 5,916 ÷ 20,116 ≈ 29.4% of generation, hydro is 14,195 ÷ 20,116 ≈ 70.6%, and wind rounds to 0.02%.

Two things about this figure deserve to be said plainly. First, hydro, not geothermal, is the backbone of Iceland's electric grid — by a ratio of more than 2:1. Any article claiming geothermal is Iceland's main electricity source has conflated it with one of the other two measurements. Second, these figures come from the agency's homepage summary, which does not label them with a year. The percentages above are arithmetic on the numbers as that summary presents them — which is why the raw GWh are shown here rather than a "29.4% in [year]" the summary does not state.

One more trap for anyone citing this data: Orkustofnun is not Iceland's energy agency anymore. The Icelandic Energy Authority closed on December 31, 2024, and the Environment and Energy Agency began operations on January 1, 2025. Orkustofnun remains the source of the historic data cited here; it is no longer the institution running Iceland's energy administration.

Heating: Where Geothermal Dominates

Electricity is where the geothermal share is smallest. Heating is where Iceland's geology pays off most directly: per Orkustofnun, about 90% of the energy used for domestic heating came from geothermal sources as of 2020. Instead of converting steam to electricity and electricity back to heat, Iceland's district heating systems pipe geothermally heated water straight into buildings.

A separate statistic often gets welded onto that one, and shouldn't be: district heating reaches 95% of Iceland's population. That is a statistic about pipe networks, not about geothermal — some district heating utilities heat their water with electricity rather than geothermal heat. So 95% of people are on district heating, and about 90% of domestic heating energy is geothermal (2020). Two different denominators. Articles that report "95% of Iceland is heated geothermally" have merged them.

The heating dominance also explains a detail in the power-plant data below: three of the geothermal stations in ÍSOR's 2023 presentation are cogeneration plants that produce hot water for district heating alongside electricity. Their thermal output — hundreds of megawatts of it — feeds the heating system without ever appearing in electricity statistics.

Primary Energy: The 70.4% Figure

The biggest of the three numbers comes from the widest measurement. Total primary energy counts everything: electricity, direct heat, and the fuel burned in transport. Iceland's 2021 breakdown, from the 2023 ÍSOR presentation (which credits the Iceland National Energy Authority as its source):

So geothermal supplied 70.4% of Iceland's total primary energy in 2021 — this is the figure behind the shorthand "Iceland runs 70% on geothermal." Stated with its label, it's correct. It's a primary-energy share, and it's large precisely because of all that direct heating: geothermal's primary-energy contribution (173.2 PJ) dwarfs hydro's (47.4 PJ) even though hydro generates most of the electricity. The same presentation puts Iceland's primary energy consumption at 661 GJ per capita.

Note what's also in that table: oil still covers 10% of Iceland's primary energy — the country hasn't engineered fossil fuels out of transport.

The Geothermal Power Stations: 755 MWe as of 2023

Iceland GeoSurvey's 2023 presentation shows seven geothermal power stations and states a total installed capacity of 755 MWe (megawatts electric). Three of the stations shown are cogeneration plants that also produce measured thermal output (MWth) for district heating:

Source: ÍSOR, 2023. The presentation states a total installed capacity of 755 MWe; its rounded station-level figures sum to 754 MWe. All figures are as of 2023; later capacity changes are not reflected here.

The cogeneration column is worth a second look. Nesjavellir alone delivers 300 MWth of heat — two and a half times its electric output. Add Hellisheiði's 133 MWth and Svartsengi's 190 MWth and these three plants supply 623 MWth of district heating capacity on top of their electricity. Describing them as power plants understates half their job, and that heat output is a big part of how the domestic-heating share reaches ~90%.

For context on this plant scale versus other geothermal technologies, see our explainer on enhanced geothermal systems, which aim to create engineered reservoirs where nature didn't provide Iceland-style ones.

Why Iceland Can Do This

Iceland sits on the divergent Mid-Atlantic Ridge where, in the broadly accepted model, the ridge meets the Iceland hotspot — a zone of mantle upwelling. The surface result, per Orkustofnun and ÍSOR, is an active volcanic and rifting belt running across the country, with magma only a few kilometers below the surface. Groundwater percolates down into hot, fractured bedrock and comes back up carrying the heat.

Along that belt, from the Reykjanes peninsula to the northeast, high-temperature fields exceed 200 °C at 1,000 meters depth. Outside the belt, low-temperature fields supply the widespread district heating.

Those conditions are a geological accident of sitting on a spreading plate boundary above a mantle hotspot — not a policy achievement another country could copy by passing the right law. Rock at 200 °C just one kilometer down is nothing like typical continental crust, where temperature climbs far more gradually with depth — our geothermal gradient explainer shows what ordinary drill holes find. Countries without Iceland's geology cannot build Svartsengi-style plants at will, which is exactly why the next section matters.

What Iceland Does — and Doesn't — Mean for Your House

Here is the conclusion not to draw from everything above: "geothermal only works in volcanic places." That reading gets the technology exactly backwards, because the word "geothermal" covers two very different machines.

Everything in this article so far is utility-scale geothermal in one volcanically active country, and it covers utility-scale power generation and cogeneration from high-temperature fields above 200 °C, plus district heating that also draws on Iceland's lower-temperature fields. The geothermal system a homeowner installs is a third, separate thing — a ground-source heat pump — and it does not need hot rock at all. A heat pump's buried loop uses the ordinary, stable temperature of shallow ground — around 50 °F in much of the US — as a heat source in winter and a heat sink in summer. No magma, no steam, no volcano. Stable shallow ground is available almost anywhere, which is why heat pumps can be installed in all climates — though every installation depends on site-specific design: loop type, soil, drilling access, heating and cooling loads, and cost.

So Iceland is not evidence that you need special geology to use geothermal at home. If anything, the relevant lesson from Iceland is about direct heat: moving heat is more efficient than making electricity to create heat, and a heat pump applies that same logic at house scale. The mechanics are covered in how geothermal heat pumps work, and the case for and against installing one — costs, efficiency, payback — in the advantages of geothermal energy.

If you leave this page with one sentence, make it this: Iceland's 200 °C steam fields and your backyard loop share a name and almost nothing else — and only one of them requires living on a plate boundary.

Frequently Asked Questions

Does Iceland run 100% on geothermal energy?

No, on any measurement. Geothermal supplied 70.4% of Iceland's total primary energy in 2021 (oil covered 10%), about 90% of energy used for domestic heating as of 2020, and roughly 29.4% of electricity generation, per the source agency's homepage summary, which shows no year for the figure.

Is geothermal Iceland's biggest source of electricity?

No — hydropower is, by more than 2:1. The generation summary on Orkustofnun's homepage lists hydro 14,195 GWh, geothermal 5,916 GWh, and wind 5 GWh, which works out to about 70.6% hydro and 29.4% geothermal. The summary shows no year for these figures.

How much of Iceland's heating is geothermal?

About 90% of the energy used for domestic heating came from geothermal sources as of 2020, per Orkustofnun. A related but different statistic: district heating networks reach 95% of the population — different because some district heating utilities use electricity rather than geothermal heat.

How many geothermal power plants does Iceland have?

Iceland GeoSurvey's 2023 presentation shows seven stations and states a total installed capacity of 755 MWe. The largest is Hellisheiði at 303 MWe plus 133 MWth of heat; three of the stations shown (Hellisheiði, Nesjavellir, Svartsengi) are cogeneration plants producing district heat alongside electricity.

Does geothermal energy only work in volcanic countries like Iceland?

No. Iceland's power plants need high-temperature fields — above 200 °C at 1,000 m depth — but residential geothermal heat pumps use the stable temperature of ordinary shallow ground, available almost anywhere — though loop type, soil, and drilling conditions are site-specific. A homeowner's ground loop has no dependence on volcanic geology.

The Bottom Line

Iceland's geothermal story is genuinely remarkable, and the shorthand "Iceland runs on geothermal" compresses it past the point of accuracy. The accurate version takes one more sentence. Geothermal provides most of Iceland's total primary energy (70.4%, 2021) and nearly all of its home heating (~90%, 2020), while hydro provides most of its electricity (~70.6%, with geothermal at ~29.4%). Every Iceland statistic you encounter belongs to one of those three categories, and it's only meaningful with its label attached. For more numbers worth getting right, see our geothermal energy facts roundup.