Air Source Heat Pumps (ASHPs) are widely regarded as one of the most energy-efficient and eco-friendly heating solutions available today. They extract heat from the outside air, drastically reducing reliance on fossil fuels. However, many homeowners are surprised when their Energy Performance Certificate (EPC) rating doesn’t reflect the high efficiency claims made by ASHP manufacturers.

Despite their real-world energy savings, there are specific reasons why ASHPs don’t always boost EPC ratings as expected.

Why Air Source Heat Pumps Should Improve EPC Ratings—But Sometimes Don’t

In theory, ASHPs should enhance EPC scores because they:

  • Have high Seasonal Coefficient of Performance (SCOP) values.

  • Use electricity more efficiently than traditional heating systems.

  • Support low-carbon objectives.

However, EPC software has limitations that can cause ASHP benefits to be understated.

Key Reasons ASHP Efficiency Doesn’t Always Reflect in EPC Scores:

1. Default SCOP Values

If specific SCOP data for the installed ASHP model isn’t provided, EPC software defaults to conservative efficiency figures. These default values may be significantly lower than the system’s actual performance.

2. Incorrect System Classification

EPC assessments differentiate between air-to-air and air-to-water heat pumps. Misclassification can lead to incorrect efficiency assumptions and lower ratings.

3. Underfloor Heating Compatibility Not Accounted For

ASHPs are most efficient when paired with low-temperature heat emitters like underfloor heating. If this configuration isn’t documented, EPC software may assume the system is operating with traditional radiators, reducing the perceived efficiency.

4. Assumptions About Auxiliary Heating

If the property has backup electric heaters or a secondary heating source, EPC assessments may assume significant usage of these systems, even if they are rarely used, diluting the impact of the ASHP.

5. Overheating and Air Tightness Penalties

In airtight homes, EPC calculations may assume an increased risk of overheating unless mechanical ventilation with heat recovery (MVHR) or other cooling strategies are documented, indirectly affecting the overall rating.

Real-World Efficiency vs EPC Methodology

ASHPs can deliver considerable energy savings and carbon reductions, but EPC assessments rely heavily on documented data and standardized assumptions. Without precise inputs, the software may not fully recognize the system’s real-world efficiency.

How to Ensure Your ASHP Is Accurately Reflected in Your EPC

  • Provide Detailed SCOP Data: Ensure that the ASHP’s seasonal efficiency values are supplied, ideally from an MCS-certified installer.

  • Document Heat Emitter Systems: Indicate whether underfloor heating or low-temperature radiators are in use to optimize efficiency recognition.

  • Clarify Auxiliary Heating Usage: Make it clear whether secondary heating systems are backup only and not in regular use.

  • Consider Airtightness and Ventilation Inputs: Supply airtightness test results and details of ventilation strategies to avoid software penalties.

EPCrate: Expert EPC Assessments for ASHP-Equipped Homes

At EPCrate, we specialize in assessing properties with air source heat pumps and renewable technologies. Our EPC services ensure that your ASHP system is fully and fairly reflected in your property’s rating.

Check our pricing options and schedule a professional assessment via our online booking platform.

Book an EPC Assessment Tailored for ASHPs

Don’t let software limitations undervalue your ASHP investment. Contact EPCrate today for an expert EPC assessment that accurately represents your heating system’s efficiency.