Skip to main content

Research Repository

Advanced Search

Challenges for the transition to low-temperature heat in the UK: A Review

Reguis, Antoine; Vand, Behrang; Currie, John



To reach net-zero emissions by 2050, buildings in the UK need to replace natural gas boilers with heat pumps and district heating. These technologies are efficient at reduced flow/return temperatures, typically 55/25 °C, while traditional heating systems are designed for 82/71 °C, and an oversized heating system can help this temperature transition. This paper reviews how heating systems have been sized over time in the UK and the degree of oversizing in existing buildings. It also reviews if lessons from other countries can be applied to the UK’s building stock. The results show that methods to size a heating system have not changed over time, but the modern level of comfort, the retrofit history of buildings and the use of margin lead to the heating system being generally oversized. It is not possible to identify a specific trend by age, use or archetype. Buildings in Scandinavia have a nascent readiness for low-temperature heat as they can use it for most of the year without retrofit. Limitations come primarily from the faults and malfunctions of such systems. In the UK, it is estimated that 10% of domestic buildings would be ready for a supply temperature of 55 °C during extreme external conditions and more buildings at part-load operation. Lessons from Scandinavia should be considered with caution. The building stock in the UK generally underperforms compared to other EU buildings, with heating systems in the UK operating at higher temperatures and with night set-back; the importance of providing a low-return temperature does not exist in the UK despite being beneficial for condensing boiler operation. Sweden and Denmark started to develop district heating technologies with limitations to supply temperatures some 40 years ago whereas the UK is only just starting to consider similar measures in 2021. Recommendations for policy makers in this context have been drawn from this review in the conclusions.


Reguis, A., Vand, B., & Currie, J. (2021). Challenges for the transition to low-temperature heat in the UK: A Review. Energies, 14(21), Article 7181.

Journal Article Type Review
Acceptance Date Oct 21, 2021
Online Publication Date Nov 2, 2021
Publication Date 2021
Deposit Date Nov 1, 2021
Publicly Available Date Nov 2, 2021
Journal Energies
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 14
Issue 21
Article Number 7181
Keywords low-temperature heat; district heating; 4th generation district heating; sizing and over-sizing heating system
Public URL


Challenges For The Transition To Low-temperature Heat In The UK: A Review (455 Kb)

Publisher Licence URL

Copyright Statement
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

You might also like

Downloadable Citations