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Glossary · Energy industry & energy transition

Large-scale heat pump

Large-scale heat pump heat pump district heating heat network Waste heat sector coupling power-to-heat

A large-scale heat pump is a heat pump with a high heat output. It supplies heat to heat networks, larger groups of buildings, neighbourhoods or industrial plants. To do so, it uses a low-temperature heat source, such as river, lake, wastewater or mine water, shallow or deep geothermal energy, industrial waste heat or ambient air. It uses electricity to raise this heat to a usable temperature. With small building heat pumps, the focus is on the individual house. A large-scale heat pump, by contrast, is usually part of an infrastructure: it feeds a heat network, supplies an industrial operation or serves as the central heat supply for several consumers. The output from which a heat pump counts as a large-scale heat pump is not defined uniformly in law. A widely cited study by Fraunhofer IEG commissioned by Agora Energiewende, for example, included systems from 500 kilowatts of heating output.

What is usually stated is the thermal output, that is, the heat output in kilowatts or megawatts. Very large systems reach double-digit megawatt values. A system with 20 megawatts of thermal output delivers 20 megawatt-hours of heat in one hour at full load. How much electricity it needs for this depends on its efficiency. The coefficient of performance (COP) indicates, for a given operating point, how much heat output the system delivers per unit of electrical power. With a COP of 3, one kilowatt-hour of electricity yields roughly three kilowatt-hours of useful heat. The remaining roughly two kilowatt-hours come from the heat source. However, source and network temperatures fluctuate over the year. For real operation, the seasonal performance factor is therefore more meaningful. It relates the heat delivered over a year to the electricity consumed in the same period. A figure on the data sheet is thus not yet proof of efficiency in operation.

Technically, the decisive factor is the temperature lift. This means the difference between the temperature of the heat source and the required flow temperature or process temperature. The smaller the lift, the more efficiently the system works. Wastewater at about 15 degrees Celsius is usually a more favourable source than cold winter air. A network that manages with 70 degrees Celsius is easier to supply than a network that permanently needs 110 degrees Celsius. How useful a large-scale heat pump is therefore does not depend on the machine alone. The heat source, the network temperatures, the return temperature, the hydraulic integration and the mode of operation matter just as much.

Distinction from heating rods, power-to-heat and CHP

Large-scale heat pumps are often equated with electric heating. This obscures the most important difference. An electrode boiler or heating rod converts electricity almost completely into heat: one kilowatt-hour of electricity becomes about one kilowatt-hour of heat. A large-scale heat pump additionally absorbs environmental heat or waste heat and raises it to a higher temperature. In this way, it generates a multiple of useful heat from the same amount of electricity. In the broader sense, both technologies count as power-to-heat, but they serve different purposes. Electrode boilers are simple in design, comparatively inexpensive, respond quickly and are suited to short periods of surplus electricity or to peak load. Large-scale heat pumps cost more to purchase and are considerably more efficient, but need a suitable heat source. They pay off above all with many operating hours per year.

The distinction from combined heat and power is also important. A CHP plant generates electricity and uses the heat produced in the process. In many district heating systems, gas- or coal-fired CHP plants were long the backbone of supply. A large-scale heat pump, by contrast, does not generate electricity; it consumes it. Heat supply thus draws less fuel and more electricity. This can reduce emissions if electricity is increasingly generated from renewable sources. At the same time, load profiles, grid connections, procurement and operational management change.

There is no sharp boundary with industrial heat pumps. An industrial heat pump is at the same time a large-scale heat pump if it delivers process heat on a large scale. The term large-scale heat pump emphasises output and integration into a central or network-based supply. The term industrial heat pump emphasises the purpose of use, such as drying, food processing, paper production or chemical processes. According to Fraunhofer IEG, the next development stage is meant to reach temperatures of up to about 200 degrees Celsius. This would also bring many drying and processing operations within reach. However, such high-temperature applications come with large temperature lifts. Efficiency is then correspondingly lower.

Significance for district heating and municipal heat planning

In district heating, large-scale heat pumps open up heat sources that would hardly be usable for individual buildings. Rivers, wastewater treatment plants, data centres, subway tunnels, industrial plants or harbour basins often provide large amounts of heat at a low temperature level. A central system can tap these sources and distribute the heat via a network. In this way, heat that would otherwise remain unused becomes a building block of local supply. In their 2023 study, Fraunhofer IEG and Agora Energiewende concluded that large-scale heat pumps could supply a large share of German district heating by 2045. However, this presupposes a significant market ramp-up. It is a potential, not a forecast.

This matters for municipal heat planning because decarbonisation cannot be reduced to individual heating appliances. In densely built-up areas, a heat network with a large-scale heat pump, heat storage, peak-load boilers and further sources can be more efficient than many individual systems. In other areas, individual supply makes more sense. A large-scale heat pump therefore does not replace every heating system across the board. It is one option within a location-specific infrastructure decision.

Whether a system pays off depends strongly on local conditions. A good heat source close to an existing network lowers development costs. Low network temperatures improve the performance factor. Large storage tanks allow longer running times when electricity is cheap. Many full-load hours spread the investment over more delivered heat. Another important factor is the ratio of electricity price to gas price. Conversely, long pipelines to the source, high flow temperatures, uncertain waste heat volumes or expensive grid reinforcements can reduce the benefit.

Legal and funding framework in Germany

For heat networks in Germany, the Heat Planning Act (Wärmeplanungsgesetz, WPG) sets binding minimum shares. The annual net heat generation of every heat network must come from renewable energies, unavoidable waste heat or a combination of the two to at least 30 percent from 1 January 2030 and to at least 80 percent from 1 January 2040 (§ 29 paragraph 1 WPG). Under certain conditions, extensions of the deadlines are possible: until the end of 2034 for the 30 percent requirement and until the end of 2044 for the 80 percent requirement. For networks that supply almost exclusively process heat to commerce and industry, the 30 percent obligation for 2030 does not apply. The Länder may set higher shares. The Act also states as a goal that, by 2030, half of grid-bound heat will be generated climate-neutrally on a federal average. For network operators, the large-scale heat pump is thus an obvious way to meet these quotas. The extent to which heat pump heat is credited in an individual case depends on the definitions of the Act.

The Federal Funding for Efficient Heat Networks (Bundesförderung für effiziente Wärmenetze, BEW) of the BAFA supports the construction of new networks with a high share of renewable energies and the decarbonisation of existing networks. In addition to investment grants, there is operating cost funding (module 4) for electrically driven heat pumps that feed into heat networks. A prerequisite is that the system was previously funded through the BEW. Funding runs for up to ten years. Funding rates, maximum amounts and technical requirements change with versions of the guideline and information sheet. For specific projects, the version currently applicable at the BAFA applies.

Power system, flexibility and grid connection

Large-scale heat pumps link the power and heat systems. They increase electricity demand but reduce the consumption of fossil fuels for heat. Final energy consumption can fall overall even though more electricity is consumed, because part of the heat comes from the environment or from waste heat. Anyone who looks only at electricity consumption therefore easily draws wrong conclusions. What matters is which fuels are replaced, which performance factor is achieved and at what times the system draws electricity.

A large-scale heat pump is particularly valuable in combination with a heat storage unit. The heat then does not have to be generated at exactly the moment it is needed. The operator can run the system more when electricity is cheap or when a lot of wind and solar power is in the grid, and store the heat temporarily. However, this flexibility does not arise by itself. It requires sufficient storage volume, suitable network temperatures, appropriate control, a reliable electricity connection and market rules that reward time-shifted operation. There is also a technical limit: many large-scale heat pumps should not be switched on and off constantly and have a minimum load. Storage and control must be matched to this.

For distribution system operators, large electric heat generators are new, significant consumers. A system with several megawatts of electrical connection capacity is not an enlarged household appliance. It requires connection planning, protection technology and metering, possibly grid reinforcement, and a mode of operation that fits the limits of the local grid. Depending on the output, a connection to a higher voltage level may be necessary. On the heat side, it must be ensured that supply remains secure even during electricity price peaks, maintenance or bottlenecks in the heat source. Peak-load and reserve plants therefore usually remain part of the overall concept.

Typical misconceptions

  • Large-scale heat pumps simply replace any fossil district heating: Many existing networks are historically designed for the high temperatures of coal, gas or waste-to-energy CHP plants. Transfer stations, radiators, controls and return temperatures help determine how far the network temperature can be lowered. Heat pumps can indeed also reach high flow temperatures, but lose considerable efficiency in doing so. Network modernisation, buildings and the generation plant must therefore be considered together.

  • Waste heat is always free and available at any time: Industrial waste heat depends on production times, locations, temperatures and ownership structures. A data centre provides a different profile than a steelworks, a wastewater treatment plant different temperatures than a chemical company. Contracts, failure risks and metering must be settled, as must the question of who pays for pipelines and heat exchangers. Only this contractual safeguarding turns technically available waste heat into a reliable source.

  • A large-scale heat pump is automatically climate-neutral: In operation, it is only as low in emissions as the electricity mix used and the displaced heat generation allow. With a high performance factor, it generally has clear advantages. With very large temperature lifts, fossil-generated electricity at peak times and short running times, the balance is worse. For investment decisions, it also matters how the electricity mix is expected to develop over the lifetime of the system.

Institutional and economic integration

With large-scale heat pumps, several areas of responsibility meet. The heat network operator plans generation, storage and network temperatures. The electricity grid operator examines connection capacity and grid compatibility. Municipalities decide on land and heat planning and are in some cases themselves owners of the utilities. Water authorities examine interventions in water bodies, groundwater or wastewater flows. The WPG explicitly takes this into account: water-law permits that are not granted within two years can justify, as a complex measure, a longer deadline for the 30 percent requirement. Network charges, levies, funding programmes, CO₂ prices and electricity market rules also help determine economic viability.

This is why projects often take longer than the delivery time of the machine would suggest. A large-scale heat pump needs a suitable source, sufficient heat demand, permits, an electricity connection, contracts and an operating strategy. If one of these building blocks is missing, good technology does not yet become a viable supply concept.

The large-scale heat pump shows that the heat transition is more than the replacement of individual heating appliances. It links local heat sources, power grids, temperature levels, storage and market incentives. Its benefit lies in efficiently generated heat where source, network and operation fit together. It is neither a simple electric heater on a large scale nor a solution for every district heating system. It is a powerful building block of a heat supply that is becoming more electric and more local and depends more on good control.

Sources

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Edited by eCMS on 12.11.2026 05:05

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