Energy carrier · Glossary

An energy carrier is a substance or form of energy in which energy is stored, transported, traded and made usable in an application. Typical examples are coal, crude oil, natural gas, biomass, heating oil, petrol, hydrogen, electricity and district heating. An energy carrier can be thought of as a means of transport: it indicates the form in which energy is moved through pipelines, tanks, grids and markets. The energy source, by contrast, indicates where the energy originally comes from, for example solar radiation, wind, hydropower or geothermal heat. The distinction is useful for teaching purposes. In official energy statistics, however, it is not applied strictly. There, renewable energies are also counted among the primary energy carriers.

Energy carriers are not interchangeable containers for the same thing. One kilowatt hour of electricity, one kilowatt hour of natural gas and one kilowatt hour of district heating each represent the same amount of energy. However, they differ in how versatile their uses are, how well they can be stored, what infrastructure they require and where their limits lie. Electricity powers electric motors, heat pumps, electrolysers and digital devices, but can hardly be held in reserve within the grid itself. Natural gas contains chemically bound energy, is easy to store and can be transported by pipeline, but releases CO₂ when burned. District heating is already heat at a certain temperature level. It is therefore tied to a heat network, local generation plants and nearby consumers.

Primary, secondary, final and useful energy

Energy carriers can be classified by their stage in the conversion chain. Primary energy carriers have not yet undergone any conversion. In German statistics these include, among others, raw coal, crude oil, natural gas, mine gas and the renewable energy carriers. Nuclear energy and waste are also treated as primary energy carriers. The energy contained in them is primary energy. One or more conversion steps turn them into secondary energy carriers such as electricity, heating oil or petrol; this is then referred to as secondary energy. A substance may appear at different stages depending on its use. Natural gas is a primary energy carrier, but is also delivered unchanged to households.

Final energy is the part of the energy that reaches the end consumer: electricity from the socket, gas at the house connection or heat from the district heating network. In statistics, final energy consumption refers to energy carriers used in the consuming sectors directly to generate useful energy. Useful energy is what is ultimately actually needed, such as space heating, light, motion or process heat. From primary energy through final energy to useful energy, a share is lost at each conversion: in the power plant, in refineries, in grids and finally in the end-use device. In addition, there is gross final energy consumption. It also includes the power plants' own consumption and line losses, and serves as the reference value for the share of renewable energies.

How statistics count wind and solar power

The AG Energiebilanzen (Working Group on Energy Balances) has compiled the German energy balance since 1995 using the internationally customary efficiency method (physical energy content method adjusted for efficiency). Fuels are in principle valued by their calorific value. Electricity from hydropower, wind and photovoltaics has no calorific value. It is therefore entered with an assumed efficiency of 100 percent: one kilowatt hour generated counts as one kilowatt hour of primary energy. For nuclear energy, by contrast, an efficiency of 33 percent is applied. One kilowatt hour of nuclear electricity is therefore booked as roughly three kilowatt hours of primary energy. The balance of electricity imports and exports is valued at 3,600 kilojoules per kilowatt hour, that is, likewise without conversion losses.

An important limitation follows for reading figures. If wind or solar power replaces fossil or nuclear generation, statistical primary energy consumption falls more than final energy consumption. This is partly due to this accounting convention, not only to energy actually saved. The shares of renewable energies in primary energy consumption and in gross final energy consumption likewise cannot simply be converted into one another. Anyone comparing energy carriers should therefore always state at which stage the measurement is made.

Technical properties

Energy carriers differ mainly in five respects: energy density, storability, transportability, losses during conversion, and usability. Liquid fuels store a lot of energy per kilogram and per litre and are easy to keep in storage. This explains their strong position in transport, especially where weight, range and fast refuelling matter. Gases such as natural gas or hydrogen require pipelines, pressure vessels or underground storage. This infrastructure is expensive and subject to strict safety rules.

Electricity occupies a special position. It is not a stockpile but a form of energy that must be provided in the grid at every moment so that generation and consumption match. Storage loosens this time constraint by temporarily converting the energy into another form. Batteries store chemical energy, pumped storage the potential energy of water, hydrogen chemical energy in a gas. Each of these conversions costs energy, needs its own facilities and ties up capital. The conversion losses are particularly high in the chain from electricity to hydrogen and back to electricity. Producing hydrogen or synthetic fuels from electricity can make sense for certain industrial processes, seasonal storage or aviation and shipping. For space heating, an electric heat pump is as a rule considerably more efficient. It uses the electricity directly and also raises ambient heat to the required temperature level.

Why the energy carrier shapes infrastructure

Each energy carrier comes with its own infrastructure:

Electricity needs grids, substations, protection technology, metering systems, balancing energy and market rules for the continuous balancing of generation and consumption.
Gas needs production or import facilities, pipelines, compressors, storage, balancing groups and safety standards.
District heating needs local heat networks, generation plants, transfer stations and long-term planning where enough heat demand comes together in a small area.

These infrastructures cannot be swapped at will. A gas heating system cannot simply be run on hydrogen just because both energy carriers are gaseous. Burners, pipes, seals, pressure levels, measuring devices and safety rules must suit the gas, and the hydrogen must actually be available on site. The choice of an energy carrier often determines for decades which facilities are built, how costs are distributed and which technical paths are economically worthwhile. Questions of regulation also follow from this: who operates the grids, who pays the network charges, which rules apply to connection and feed-in? These rules differ by country, energy carrier and grid level and must be checked in each individual case.

There are also statistical particularities. After being fed in, electricity and biomethane mix with electricity or methane from other sources and can no longer be physically distinguished. In the German energy balance, fed-in biomethane is therefore counted as natural gas and green electricity as electricity. Anyone who buys biomethane with certain environmental properties receives these through a mass balance system, that is, purely on paper. The origin is allocated to the quantity delivered, without it having to be the same molecules.

Common oversimplifications

First, energy carriers are often compared only by the price for end customers. The price at the pump, at the gas meter or on the electricity bill is made up of taxes, levies, network costs and procurement costs in different proportions depending on the energy carrier. A low price per kilowatt hour says little about how efficiently an energy carrier is ultimately used. What matters is the cost per unit of useful energy, for example per heated room or per kilometre driven. In addition there are costs that do not appear in the price at all, for example for reserve capacities or grid bottlenecks.

Second, renewable is often equated with unlimited availability. Renewable electricity can replace large amounts of fossil energy, but remains tied to land, facilities, grids, weather, storage and permits. If hydrogen, synthetic methane or fuels are produced from it, the usable amount of energy shrinks with every conversion step. Such energy carriers can be valuable for applications that are hard to electrify, but they are not a loss-free substitute for fossil fuels.

Third, it is assumed that the energy carrier alone determines the climate impact. Hydrogen releases no CO₂ when used, whether in a fuel cell or during combustion. However, nitrogen oxides can arise during combustion. Its climate balance depends mainly on how it was produced. Electricity, too, is emission-free at the point of consumption; its emissions arise earlier, depending on the generation mix. Biomass is renewable, but limited by land, competing uses and ecological limits. The energy carrier thus describes the form in which energy is provided, not the ecological quality of the entire chain.

Significance for electrification and security of supply

The energy transition shifts the weights between energy carriers. Heat pumps replace oil and gas heating, electric vehicles replace combustion engines and electric processes replace fossil process heat, as far as temperature and process allow. Because electric motors and heat pumps use the energy supplied better than combustion technology, electricity consumption can rise while total final energy consumption nevertheless falls. For the power system, what matters is not only the quantity of electricity but also when it is needed and how well consumption can be adapted to supply. This adaptability is called flexibility.

Energy carriers that can be stored well remain important for security of supply: for seasonal fluctuations, for Dunkelflauten (prolonged periods with little wind and sun), for industrial high-temperature processes and as a strategic reserve. This does not mean that every fossil energy carrier in use today must be replaced one to one by a renewable gas. For each application it must be examined whether direct electrification, heat networks, storage, load shifting or a chemical energy carrier is the technically and economically suitable solution. Anyone who distinguishes energy carriers cleanly can better recognise where electricity can be used directly, where storable molecules are needed, which losses are unavoidable and which costs are hidden by hasty equations.

Sources

Definitionen/Methodik (FAQ) — AG Energiebilanzen e. V.; 2023-05-25. FAQ-Abschnitte zur Wirkungsgradmethode, zum Außenhandel mit erneuerbaren Energieträgern, zum Bruttoendenergieverbrauch und zu Heizwerten
Glossar: Primärenergieverbrauch — Umweltbundesamt; unbekannt. Glossareintrag Primärenergieverbrauch
Energie (Datenseite) — Umweltbundesamt; unbekannt. Einleitung und Indikatoren Endenergie- und Primärenergieverbrauch
Ziel 7 – Bezahlbare und saubere Energie — Statistische Ämter des Bundes und der Länder; unbekannt. Definitionen Primärenergieverbrauch und Endenergieverbrauch
Auswertungstabellen zur Energiebilanz Deutschland — AG Energiebilanzen e. V.; unbekannt. Methodische Vorbemerkung zur Wirkungsgradmethode (laut Suchergebnis)

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Edited by eCMS on 11.11.2026 19:46