Guidance

Home Energy Model: technical documentation

Technical documents providing detail on how a home’s energy performance is calculated using the Home Energy Model (HEM).

• From: Department for Energy Security and Net Zero
• Published: 13 December 2023
• Last updated: 29 October 2025 — See all updates

Documents

HEM-TP-01 General summary of core calculation (updated October 2025)

PDF, 315 KB, 12 pages

HEM-TP-02 General summary of wrappers (updated October 2025)

PDF, 274 KB, 8 pages

HEM-TP-03 External conditions (updated October 2025)

PDF, 292 KB, 9 pages

HEM-TP-04 Space heating and cooling demand

PDF, 554 KB, 16 pages

HEM-TP-05 Fabric heat loss (updated October 2025)

PDF, 473 KB, 16 pages

HEM-TP-06 Infiltration and ventilation heat loss (updated October 2025)

PDF, 626 KB, 22 pages

HEM-TP-07 Thermal mass (updated October 2025)

PDF, 387 KB, 12 pages

HEM-TP-08 Solar gains and shading (updated October 2025)

PDF, 747 KB, 20 pages

HEM-TP-09 Energy for domestic hot water

PDF, 165 KB, 9 pages

HEM-TP-10 Ductwork and pipework losses (updated October 2025)

PDF, 394 KB, 14 pages

HEM-TP-11 Hot water storage tanks

PDF, 339 KB, 13 pages

HEM-TP-12 Heat pump methodology

PDF, 438 KB, 30 pages

HEM-TP-13 Storage heaters

PDF, 285 KB, 12 pages

HEM-TP-14 Boiler methodology (updated October 2025)

PDF, 565 KB, 21 pages

HEM-TP-15 Heat batteries

PDF, 175 KB, 12 pages

HEM-TP-16 Heat emitters

PDF, 275 KB, 14 pages

HEM-TP-17 Controls

PDF, 198 KB, 13 pages

HEM-TP-18 PV generation and self-consumption

PDF, 382 KB, 15 pages

Details

29 October 2025

We have republished some of the technical documents to reflect changes in the methodology since the Home Energy Model consultation. For further details see the government response to the consultation.

The consultation on the proposed Home Energy Model closed in March 2024 and we published the summary of responses and the government response to it in October 2025.

We will update and add to this technical documentation throughout the model development process.

Published 13 December 2023

Last updated 29 October 2025 + show all updates

1. 29 October 2025

   We have republished some of the technical documents to reflect changes in the methodology since the Home Energy Model consultation. For further details see the government response to the consultation (linked in page).

2. 13 December 2023

   First published.