When to Include Small Scale Hydro

As renewable energy technologies become increasingly diverse, domestic energy assessors are encountering a wider array of systems during their assessments. 

One such technology, small-scale hydro, is now explicitly recognised within the RdSAP (Reduced Data Standard Assessment Procedure) methodology. This inclusion ensures that the energy contributions from such systems are accurately reflected in a dwelling's Energy Performance Certificate (EPC).

With the introduction of RdSAP 10 and Version 12 of the conventions, effective from 1st May 2025, specific guidance has been provided for the recording of small-scale hydro systems.

Convention Reference and Recording Requirements:

The inclusion and recording of small-scale hydro systems are governed by Convention 9.07b. This convention simplifies the assessment process for this technology, stating:
"Hydro systems can be recorded as a simple yes/no, along with basic documentary evidence confirming its presence. No usage information is required."

This means that for qualified assessors, the process of including a small-scale hydro system is straightforward:

1. Confirmation of Presence: Verify that a small-scale hydro system is installed at the property.

2. Basic Documentary Evidence: Obtain and retain basic documentary evidence that confirms the existence of the system. This could include installation certificates, commissioning documents, or other official records that clearly indicate the system's presence.

3. Simple Input: Record the presence of the hydro system as a simple 'yes' or 'no' within the RdSAP software. Unlike some other renewable technologies, there is no requirement to gather detailed usage data or specific technical specifications (e.g., power output in kWp) for the assessment calculation.

Important Considerations for Assessors:

• Appendix Q: It is important to note that Convention 9.07b specifically states that if small-scale hydro is specified via Appendix Q of the SAP specification document, then the simplified approach outlined in 9.07b would not apply. Instead, assessors would need to refer to Technical Note 08 (as mentioned in Appendix 5 of the Conventions), which provides detailed instructions for technologies recognised through the Appendix Q mechanism. However, for most standard small-scale hydro installations encountered, Convention 9.07b will be the primary reference.

• Visual Confirmation: While documentary evidence is key, visual confirmation of the system's components (e.g., water intake, turbine, generator) where accessible, can support the assessment.

• Professional Judgement: As with all aspects of an energy assessment, assessors should apply professional judgement to ensure that the system genuinely qualifies as small-scale hydro and that the documentary evidence is credible.

By adhering to Convention 9.07b, qualified assessors can efficiently and accurately incorporate the presence of small-scale hydro systems into their energy assessments, contributing to a more comprehensive and representative EPC for the dwelling.