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: 3 March 2026 — See all updates

Documents

HEM-TP-01 General summary of core calculation

PDF, 315 KB, 12 pages

HEM-TP-02 General summary of wrappers

PDF, 274 KB, 8 pages

HEM-TP-03 External conditions

PDF, 292 KB, 9 pages

HEM-TP-04 Space heating and cooling demand

PDF, 454 KB, 16 pages

HEM-TP-05 Fabric heat loss

PDF, 555 KB, 18 pages

HEM-TP-06 Infiltration and ventilation heat loss

PDF, 626 KB, 22 pages

HEM-TP-07 Thermal mass

PDF, 387 KB, 12 pages

HEM-TP-08 Solar gains and shading

PDF, 747 KB, 20 pages

HEM-TP-09 Energy for domestic hot water

PDF, 287 KB, 10 pages

HEM-TP-10 Ductwork and pipework losses

PDF, 394 KB, 14 pages

HEM-TP-11 Hot water storage tanks

PDF, 445 KB, 18 pages

HEM-TP-12 Heat pump methodology

PDF, 843 KB, 39 pages

HEM-TP-13 Storage heaters

PDF, 367 KB, 12 pages

HEM-TP-14 Boiler methodology

PDF, 565 KB, 21 pages

HEM-TP-15 Heat batteries

PDF, 430 KB, 22 pages

HEM-TP-16 Heat emitters

PDF, 413 KB, 19 pages

HEM-TP-17 Controls

PDF, 350 KB, 15 pages

HEM-TP-18 PV generation and self-consumption

PDF, 701 KB, 21 pages

Details

3 March 2026

All technical documents have now been republished 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 3 March 2026 + show all updates

1. 3 March 2026

   All technical documents have now been republished to reflect changes in the methodology since the Home Energy Model consultation.

2. 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).

3. 13 December 2023

   First published.