Energy calculation as a service ECaaS
ECaaS provides an API to the Home Energy Model so users can produce software, and a basic frontend so users can validate building designs.
Energy Calculation as a Service (ECaaS) is a calculator service run by MHCLG (Ministry of Housing, Communities, and Local Government) that provides a performant implementation of the Home Energy Model (HEM), a methodology for predicting the energy performance of buildings, for various future statutory purposes including, but not limited to, calculating compliance with the Future Homes Standard (FHS).
The service takes the form of an API that can be used by authorised bodies to build software for statutory purposes that require calculations using the Home Energy Model. The service will become the only valid means to confirm compliance with Part L of the Building Regulations when referring to the Future Homes Standard. For other users, the underlying software libraries are open source and can be used to conduct calculations for non-statutory purposes.
For access to the ECaaS API contact ECaaS@communities.gov.uk
The Rust library used by ECaaS, developed within MHCLG, can be found on GitHub, and the Python implementation written by BRE under commission from DESNZ (Department of Energy Security and Net Zero) is published on BRE’s Azure DevOps space.
A basic web frontend is being developed to support stakeholders as they familiarise themselves with the HEM methodology and work out the impact on the types of home that they are building.
This article is based on the UK government "Guidance Energy calculation as a service (ECaaS): Access the Home Energy Model" published on 3 February 2025.
[edit] Related articles on Designing buildings
- Air permeability testing.
- Air tightness.
- Applying Fabric First principles: Complying with UK energy efficiency requirements FB 80.
- Approved building energy calculation software.
- Approved documents.
- Building Regulations.
- Building Research Establishment.
- Brief notes on proposed changes to EPCs.
- Changes in SAP 10.
- Co-heating test.
- Conventions for U-value calculations (2006 edition) BR 443.
- Dynamic Simulation Model.
- Emission rates.
- Energy efficiency of traditional buildings.
- Energy Performance Certificates.
- Energy Performance of Buildings Directive.
- Home Energy Model comparisons: SAP 10.2, PHPP, ESP-r and the new HEM.
- IHBC responds to Energy Company Obligation ECO4 and PAS 2035.
- Minimum energy efficiency standard (MEES).
- National Calculation Method.
- Passivhaus vs SAP.
- Standard Assessment Procedure SAP.
- Simplified Building Energy Model.
- Target fabric energy efficiency rate.
- The Home Energy Model and Future Homes Standard assessment wrapper.
- Thermal dynamic analysis.
- U-value conventions in practice: Worked examples using BR 443.
- What is the new Home Energy Model or HEM?.
Featured articles and news
The 5 elements of seiri, seiton, seiso, seiketsu and shitsuke.
Shading for housing, a design guide
A look back at embedding a new culture of shading.
The Architectural Technology Awards
The AT Awards 2025 are open for entries!
ECA Blueprint for Electrification
The 'mosaic of interconnected challenges' and how to deliver the UK’s Transition to Clean Power.
Grenfell Tower Principal Contractor Award notice
Tower repair and maintenance contractor announced as demolition contractor.
Passivhaus social homes benefit from heat pump service
Sixteen new homes designed and built to achieve Passivhaus constructed in Dumfries & Galloway.
CABE Publishes Results of 2025 Building Control Survey
Concern over lack of understanding of how roles have changed since the introduction of the BSA 2022.
British Architectural Sculpture 1851-1951
A rich heritage of decorative and figurative sculpture. Book review.
A programme to tackle the lack of diversity.
Independent Building Control review panel
Five members of the newly established, Grenfell Tower Inquiry recommended, panel appointed.
Welsh Recharging Electrical Skills Charter progresses
ECA progressing on the ‘asks’ of the Recharging Electrical Skills Charter at the Senedd in Wales.
A brief history from 1890s to 2020s.
CIOB and CORBON combine forces
To elevate professional standards in Nigeria’s construction industry.
Amendment to the GB Energy Bill welcomed by ECA
Move prevents nationally-owned energy company from investing in solar panels produced by modern slavery.
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.