On 14th May 2025, the Department for Energy Security and Net Zero (DESNZ) announced that both SAP 10 and the Home Energy Model (HEM) could be used in England to assess compliance with the upcoming Future Homes Standard. Elmhurst takes a closer look at why SAP 10.3 is being developed and what we can expect from it.

Looking back

Over the winter of 2023-2024 the Government ran a consultation proposing to replace SAP with the Home Energy Model. This would include a new wrapper to utilise the Home Energy Model specifically for the purpose of calculating compliance with the Future Homes Standard. Since the consultations closed in March 2024, the Ministry of Housing, Communities and Local Government (MHCLG) have been creating their own version of the Home Energy Model which accreditation schemes will link their front end systems to, in order to calculate compliance to the Future Homes Standard. In November 2024 this facility (known as “Energy Calculations as a Service”) was made available to accreditation schemes. Running alongside this was the development of the core Home Energy Model by BRE, which has undergone two revisions since Energy Calculations as a Service was launched.

What is SAP 10.3 - Assessor working at desk

Why is SAP 10.3 being developed?

For the Home Energy Model to be confidently used for compliance purposes, Elmhurst believes several key items must be in place. These include:

A complete set of Conventions.
A complete and available Product Characteristic Database (PCDB).
A complete wrapper which sets the user input fields needed to calculate compliance.

Currently, all of these items are either in development or yet to commence, therefore using the Home Energy Model in its current state would likely lead to a high level of confusion. This is particularly concerning at a time when builders require consistent and reliable outcomes to support their future developments and meet the Government’s targets for house building.

To address this gap, a modified version of SAP 10 (known as SAP 10.3) is being developed. The use of the established SAP 10 methodology will ensure a smoother transition to the Future Homes Standard and ensure the Home Energy Model is fully completed before it is used to calculate compliance with the Future Homes Standard.

What can we expect from SAP 10.3?

Elmhurst anticipates that SAP 10.3 will contain:

A new notional dwelling used to set the primary energy, carbon emission and fabric energy efficiency targets of the upcoming Future Homes Standard.
Revised carbon emission and primary energy factors for fuels used, currently contained in Table 12 of the SAP 10.2 specification.
A new version of the BREL report to clearly show SAP 10.3 has been used to calculate compliance with the Future Homes Standard.

We expect SAP 10.3 and the Future Homes Standard to be delivered in the second half of 2025.

At present, there is no confirmed timescale for the delivery of the Home Energy Model. However, once deemed ready, both HEM and SAP 10.3 will be able to demonstrate compliance with the Future Homes Standard.

Elmhurst’s Thoughts

Jason Hewins, New Build Dwellings Manager, comments:

“Elmhurst is pleased that we now have some clarity as to how compliance with the Future Homes Standard will be demonstrated. We have been liaising closely with Government to assist with the implementation of the Home Energy Model and stressed the importance of a fully completed methodology and set of conventions if it is to be used to demonstrate compliance with the Future Homes Standard.

The option to use SAP 10.3 to demonstrate compliance is a pragmatic approach that should give some reassurance to assessors and builders. This will allow homes to be assessed against the new standards using a methodology that is robust and well established in the industry until the Home Energy Model is complete. This will ultimately deliver homes more quickly against the Future Homes Standard.

Elmhurst will be updating our Design SAP 10 application to incorporate the SAP 10.3 methodology. We will also continue to develop our HEM application, so it is ready for when HEM is deemed suitable to be used for the Future Homes Standard.”