Understanding What SAP 11 Expects From Heat Pump Modelling

SAP 11 is the latest version of the UK’s Standard Assessment Procedure for residential energy performance. It reflects updated thinking on how heat pumps behave in real homes by placing more emphasis on seasonal efficiency and suitable temperature operation.

To comply, heat pumps must be modelled using:

accurate SCOP values that represent seasonal heating efficiency
realistic flow and return temperatures, especially for low-temperature operation
appropriate part-load behaviour to reflect actual system dynamics

These inputs help determine whether a heat pump can meet carbon and primary energy targets for a given dwelling type.

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Why Flow Temperature Is Critical for Compliance

Unlike boiler systems, heat pumps are highly sensitive to operating temperatures. SAP 11 recognises this by making flow temperature a central input in the compliance calculation. Lower temperatures typically improve heat pump efficiency, but they must be achievable with the existing or planned emitters in the home.

This creates a need to verify:

whether the building’s distribution system supports low-temperature operation
the impact of emitter upgrades on achievable SCOP
seasonal behaviour under different demand profiles

See how modelling helps engineers evaluate realistic temperature scenarios ›

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Using System Modelling To Predict Real Performance

House-level compliance results depend on more than heat pump labels alone. System modelling helps engineers understand how the heat pump interacts with emitters, pipework and controls, ensuring the SAP 11 inputs reflect the home’s real characteristics.

Modelling can support:

correct selection of heat pump capacity
evaluation of multiple flow temperature strategies
prediction of seasonal efficiency under realistic conditions
identification of upgrades needed for compliance

This avoids assumptions that might lead to non-compliance or underperformance after installation.

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What This Means for Residential Designers

SAP 11 shifts the focus from nominal heat pump ratings to system-specific performance. Designers must therefore combine manufacturer data with engineering insight to build a realistic picture of heating behaviour throughout the year.

Discover how advanced simulation supports accurate residential HVAC design ›

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FAQ: SAP 11 Heat Pump Modelling

Does SAP 11 Require Lower Flow Temperatures for All Homes?

Not automatically, but lower temperatures typically improve efficiency. SAP 11 requires that chosen temperatures are realistic for the actual emitters in the dwelling.

Can Manufacturer SCOP Values Be Used Directly?

Yes, but only if they reflect the intended operating conditions. If temperatures or control strategies differ, the SCOP used in modelling may need adjustment.

Does SAP 11 Apply Only to New Builds?

No. It applies to new dwellings and to certain retrofit scenarios where energy-performance compliance must be demonstrated.

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