When it comes to assessing a building’s energy efficiency, two primary methodologies dominate the UK’s Energy Performance Certificate (EPC) landscape: SAP (Standard Assessment Procedure) and SBEM (Simplified Building Energy Model). While both are official government-approved systems, they cater to different property types and use different inputs and assumptions, leading to debates about which is more accurate.
In this guide, we’ll explore the key differences between SAP and SBEM, how they apply to domestic vs. non-domestic EPCs, and whether one is truly more accurate or useful than the other.
What Is SAP?
SAP is the Standard Assessment Procedure used to calculate EPC ratings for residential dwellings. It evaluates:
Fabric insulation and thermal performance
Heating system type and efficiency
Hot water provision
Lighting
Renewable technologies (e.g., solar PV, heat pumps)
SAP calculations are based on standard occupancy, climate, and usage assumptions to ensure comparability across homes.
➡ Learn more about our residential EPC process on our EPC Assessors London page.
What Is SBEM?
SBEM is used for commercial or non-domestic properties. It analyses:
Building size and layout
HVAC systems
Lighting control systems
Zoning and usage types
Occupancy schedules and load profiles
SBEM uses more granular input on building operation and is applied through tools like iSBEM or other approved software.
If you’re unsure which method your property requires, our team can advise during the booking process.
SAP vs SBEM: Key Differences
| Feature | SAP (Domestic) | SBEM (Non-Domestic) |
|---|---|---|
| Target Building Type | Houses, flats, apartments | Offices, retail, schools, etc. |
| Calculation Inputs | Fixed assumptions (occupancy, climate) | Variable inputs (usage, controls, hours) |
| System Complexity | Simpler | More complex and detailed |
| Renewable Technology Impact | High | Moderate |
| Accuracy on Real Usage | Lower | Higher (if well-modelled) |
Which Is More Accurate?
Accuracy depends on context.
For standard residential buildings, SAP offers consistent comparisons, but critics argue it’s out of touch with real energy consumption, especially in homes with unusual occupancy patterns or older heating systems.
For commercial spaces, SBEM is often seen as more flexible and reflective of actual usage—but it also allows for more variation and subjectivity in input, which can affect consistency.
In essence:
SAP is more standardised
SBEM is potentially more accurate for complex usage scenarios
EPC Implications
The choice between SAP and SBEM isn’t optional—it’s dictated by property type. However, understanding the model helps property owners:
Interpret EPC results more clearly
Plan effective upgrades
Address low scores with realistic expectations
At EPCrate.co.uk, our accredited assessors are qualified in both methodologies and can guide you on what’s best for your property.
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Whether you’re a homeowner looking to boost your EPC score or a business owner seeking to meet regulatory compliance, our expert team can help.
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