If you’re booking an Energy Performance Certificate (EPC), you may come across two terms: SAP and RdSAP. Both are assessment methodologies used to calculate the energy efficiency of buildings in the UK—but they’re not the same. Understanding the difference is key to knowing what applies to your property and ensuring EPC compliance.
Let’s break down the distinction between SAP and RdSAP, when each is used, and why it matters for landlords, homeowners, and developers alike.
🧮 What Is SAP?
SAP stands for Standard Assessment Procedure. It’s the full methodology used for calculating the energy efficiency of newly constructed homes or majorly refurbished buildings.
🏗️ Key SAP Characteristics:
Used for new builds or conversions
Based on full construction specs and architectural plans
Calculates energy use for space heating, hot water, lighting, and renewables
Required for Building Regulations compliance
Typically conducted before construction is complete
📄 SAP Outputs:
A detailed EPC (Energy Performance Certificate)
A Predicted Energy Assessment (PEA) during pre-build
A full breakdown of building elements, U-values, and efficiency ratings
🔍 What Is RdSAP?
RdSAP stands for Reduced Data SAP. As the name suggests, it’s a simplified version of SAP used for existing dwellings where full construction data isn’t available.
🏡 Key RdSAP Characteristics:
Used for existing homes during resale or rental
Relies on site surveys and visual inspection
Quicker and more cost-effective
Suitable for standard EPC requirements for landlords or sellers
Typically delivered in 1 site visit
🧾 RdSAP Outputs:
A valid EPC certificate for existing buildings
Recommendations for improvements
Energy rating from A (most efficient) to G (least efficient)
🆚 SAP vs. RdSAP: Quick Comparison Table
| Feature | SAP | RdSAP |
|---|---|---|
| Used For | New builds / conversions | Existing homes |
| Data Type | Full spec & design data | Visual survey & assumptions |
| Accuracy | High (detailed inputs) | Moderate (estimated values) |
| Cost | Higher (longer assessment time) | Lower (quicker inspection) |
| Required For | Building Regulations approval | EPCs for sale/rent compliance |
| Assessment Timing | During or before construction | After construction |
🧠 Why It Matters for EPC Compliance
Choosing the correct method ensures:
You meet regulatory requirements
Your EPC is valid and accepted
You avoid delays when renting or selling
You get accurate recommendations for energy improvements
Using RdSAP for a new build would be invalid, and using SAP for a simple resale EPC would be overkill—and more expensive.
🔧 Need Help Choosing the Right Assessment?
At EPCRate.co.uk, we help property owners across London determine the correct EPC type—SAP or RdSAP—based on:
Property status (new vs. existing)
Planning permission or change-of-use
Refurbishment level
Legal or rental obligations
✅ Book a certified assessor today
✅ Same-day EPCs for sales or rentals
✅ Guidance on MEES and EPC upgrades
📞 Still unsure whether you need SAP or RdSAP?
Contact us for free advice—we’re here to make EPC compliance simple.
