Around half of the world's energy is used as heat: to warm buildings, power industrial processes, produce steam, provide hot water and run district heating. Yet the energy transition conversation is dominated by electricity.
Heat is Half exists to make this imbalance visible.
When we talk about energy, we picture power lines, wind turbines and solar panels. But electricity is only about a fifth of the energy Europe actually consumes. Transport takes roughly another third. The single largest share, about half, is heat.
Heating & cooling, transport and electricity as shares of final energy demand.
| Use | Share of final energy |
|---|---|
| Heat (heating & cooling) | ≈ 50% |
| Transport | ≈ 30% |
| Electricity | ≈ 20% |
Source: European Environment Agency. Heating and cooling account for about half of final EU energy use.
Space heating and hot water dominate household energy use. Buildings consume over 40% of all final energy in the EU.
Steel, cement, chemicals, food and paper, much of it at temperatures only fuels currently provide.
Networks that supply whole neighbourhoods and cities with heat, still fuelled by fossil sources in most of Europe.
We are used to thinking of energy as electricity: power plants, grids, batteries, demand. But the thermal half of the energy system has exactly the same anatomy of its own. Once you see it, the heat transition stops being a footnote to electrification and becomes a system to build.
Usable heat can come directly from solar thermal collectors, geothermal resources, ambient heat captured by heat pumps, and heat recovered from industry, data centres and wastewater.
Heat moves through its own physical systems: pipes and heat networks, building installations, and the steam and process-heat systems that run industry.
Heat can be stored directly, cheaply and at enormous scale. Large seasonal stores connect summer's renewable heat supply with winter's demand, in a way batteries cannot.
Heat demand is not one thing. Homes need space heating and hot water, cities need network-scale heat, and industry needs process heat across a huge range of temperatures.
Because most heat is still produced by burning coal, oil and gas, heat carries an enormous climate footprint, larger than electricity generation or transport.
Each square is 1% of the world's energy-related CO₂ emissions, 2024.
of the world's energy-related CO₂ emissions came from producing heat in 2024.
| Category | Share of energy-related CO₂ (2024) |
|---|---|
| Heat production | 37% |
| All other energy uses | 63% |
Source: IEA, Renewables 2025. Heat accounted for almost half of total final energy consumption and 37% of energy-related CO₂ emissions in 2024.
In EU households, more than half of heating energy (57%) was supplied by systems burning fossil fuels directly. Even in district heating plants, fossil fuels made up over two thirds of everything burned.
Household heating energy by source, EU 2020, with fossil fuels highlighted in red.
| Source | Share of household heating, EU 2020 |
|---|---|
| Natural gas (fossil) | 39% |
| Heating oil (fossil) | 15% |
| Coal (fossil) | 4% |
| All other sources | ≈ 43% |
Source: European Environment Agency, “Decarbonising heating and cooling — a climate imperative” (data for 2020). Individual shares are rounded and may not sum exactly to 100.
Renewable share of heat consumption. Grid marks every 10%.
| Region | Renewable share of heat |
|---|---|
| EU heating & cooling (2020) | 23% |
| World heat (2024) | 14% |
Sources: EEA (EU, 2020) · IEA Renewables 2025 (world, 2024).
Clean heating is not a distant dream. It is the status quo in parts of Europe. Sweden and Estonia heat with mostly renewable energy today, while Ireland and the Netherlands remain almost entirely dependent on fossil fuels. The leaders share a pattern: they built thermal infrastructure, district heating networks that can absorb renewable and recovered heat. The technology gap is zero. The deployment gap is enormous.
Share of heating & cooling energy from renewable sources, 2024, EU-27 plus Iceland and Norway.
A nine-fold spread between member states, with the same technologies available to all of them.
| Country | Renewable share of H&C, 2024 |
|---|---|
| Iceland* | 79.5% |
| Sweden | 67.8% |
| Estonia | 67.8% |
| Finland | 62.6% |
| Latvia | 61.8% |
| Malta | 59.2% |
| Denmark | 56.4% |
| Lithuania | 52.1% |
| Portugal | 47.0% |
| Cyprus | 42.3% |
| Austria | 42.2% |
| Norway* | 35.2% |
| Croatia | 34.8% |
| Bulgaria | 34.2% |
| Slovenia | 33.7% |
| Greece | 32.6% |
| France | 31.3% |
| Czechia | 29.1% |
| Romania | 28.1% |
| EU-27 average | 26.7% |
| Hungary | 22.6% |
| Spain | 21.6% |
| Poland | 21.3% |
| Slovakia | 20.4% |
| Italy | 20.2% |
| Luxembourg | 19.0% |
| Germany | 17.7% |
| Netherlands | 11.3% |
| Belgium | 11.3% |
| Ireland | 7.9% |
* Non-EU country, reported in the same Eurostat dataset.
Source: Eurostat, SHARES 2024, share of energy from renewable sources in heating and cooling (nrg_ind_ren, REN_HEAT_CL). Values rounded to one decimal.
Industry doesn't need "heat". It needs specific temperatures: 85°C to pasteurise milk, 200°C to dry paper, 1,450°C to make cement. No single technology replaces fossil heat across that range. Instead, a portfolio does: solar thermal, geothermal and waste heat in the low and medium range, heat pumps and electric boilers alongside them, and high-temperature electrification where nothing else reaches.
Temperature coverage of clean heat resources (°C), with fossil combustion as reference.
▌ 37% of EU final energy demand for process heating is below 200°C (≈722 TWh), within reach of solar thermal, geothermal, waste heat and heat pumps today
| Resource | Temperature coverage | Status |
|---|---|---|
| Solar thermal | up to ≈150°C standard · ≈400°C concentrating | Commercial |
| Geothermal (direct use) | typically up to ≈150°C | Commercial |
| Industrial heat pumps | up to ≈200°C (300°C by ~2035) | Commercial / R&D |
| Electric boilers | up to ≈500°C | Commercial |
| Resistance / induction / arc | ≈100–1,800°C+ | Commercial (sector-specific) |
| Fossil combustion (reference) | 0–1,800°C+ | To be replaced |
Sources: EHPA, Industrial Heat Pumps position paper (2025): 37% of EU process-heat energy demand < 200°C ≈ 722 TWh; heat pumps up to 200°C today, 300°C expected by 2035 · Solar Heat Europe: collector ranges ≈150°C / ≈400°C; ≈half of industrial heat needs within solar thermal range · Agora Industry & Fraunhofer ISI, “Direct electrification of industrial process heat” (2024): 62% electrifiable with existing technology; electric boilers ≈500°C; electric arc furnaces 1,800°C. Temperature ranges and process temperatures are typical values.
Heat has its own sources, its own infrastructure, its own storage and its own demand. The way forward is to build that system: direct renewable heat, recovered heat, thermal networks and thermal storage, with efficient electrification where it is technically and economically the right tool. There is no single replacement for fossil heat. There is a portfolio.
Solar thermal captures solar energy directly as useful heat, rather than first generating electricity. Not because it is always the better choice, but because it shows something fundamental: heat does not have to be treated as an electricity problem. Standard collectors deliver up to ~150°C; concentrating collectors reach ~400°C, a range that covers roughly half of the world's industrial heat needs.
Rooftop collectors supplying homes and commercial buildings with heat and hot water, year after year, at zero fuel cost.
Field-scale collector plants feeding entire heat networks, pioneered in Denmark where over 60% of homes are on district heating, often combined with seasonal pit storage that carries summer sun into winter.
Hot water and steam for food, textiles, chemicals and more: the low- and medium-temperature demand where most industrial heat is used.
Sources: Solar Heat Europe (collector temperature ranges; share of industrial heat needs) · SolarPACES (Danish district heating).
Sunlight captured directly as useful heat. From rooftop hot water to field-scale district heating and industrial steam. See above.
Steady heat from underground, available day and night, season after season, for buildings, heat networks and low- and medium-temperature industry.
A technology for accessing renewable heat that already surrounds us: air, water and ground. Electricity is the lever, not the source: 3–4 units of heat per unit of electricity, and the EU's fastest-growing renewable heating technology.
The EU discards ≈2,860 TWh of excess heat every year, from industry, data centres and wastewater. That is almost as much as all its buildings need for heat and hot water. Recovering it is a resource, not a technology problem.
Thermal networks are the infrastructure of the heat transition: they can feed any local heat source (solar, geothermal, waste heat, large heat pumps) into whole neighbourhoods at once.
Radiators, hot-water systems, steam lines and process-heat installations are infrastructure too. Modernising them, and lowering their temperatures, opens the door to every renewable heat source.
Heat, unlike electricity, is cheap to store at scale. Water tanks buffer days; seasonal pit and underground stores carry summer sun into winter, and take pressure off the electricity grid.
The cheapest and cleanest heat is the heat we never need: renovation, insulation, smarter controls and lower network temperatures shrink the problem before we solve it. What remains, from homes to high-temperature industry, is matched to the resources above.
Heat is half of final energy. Electricity is a fifth.
Myth 02 · Not necessarilySolar thermal captures solar energy directly as useful heat.
Myth 03 · It canTanks, pit storage and underground stores carry summer into winter.
Myth 05 · FalseElectricity is the lever, not the source: 3–4 units of heat per unit.
“We cannot complete the energy transition by transforming electricity alone. Heat is half.”
Heat has its own sources, networks, storage and demand. Treat it as a system, and the missing half of the energy transition comes into view. Bring it into the conversation: in policy, in planning, in every discussion about the energy transition.