Rinnai calls for common approach to predicting whole-system SPF
UK – Rinnai UK is bringing together heating industry specialists to develop a common methodology for predicting whole-system Seasonal Performance Factor (SPF), with a closed-door roundtable scheduled for elementalLONDON on 25 November 2026.
The 90-minute session will examine inconsistencies in current calculation approaches and seek agreement on a transparent, independently credible method for comparing predicted heat pump system performance on commercial projects.
Addressing inconsistencies in SPF predictions
Although established frameworks such as SEPEMO define different system boundaries, Rinnai argues that the industry lacks a single, consistently applied method for predicting whole-system SPF at the design stage. Differences in weather data, load profiles, flow temperatures, storage losses, controls, backup heating and auxiliary electricity consumption can produce varying results for the same proposed installation. The company believes a common methodology should establish consistent calculation boundaries, inputs, assumptions and reporting requirements, allowing consultants to produce comparable and repeatable predictions.
We are not asking the industry to accept a Rinnai number or methodology. We are asking the industry to help create a transparent method that any competent consultant can apply, explain and defend.
Chris Goggin, Rinnai UK
Looking beyond heat pump efficiency
While coefficient of performance (COP) measures efficiency at a defined operating point and seasonal coefficient of performance (SCOP) assesses performance under standardised seasonal conditions, whole-system SPF can account for additional energy consumption associated with pumps, controls and backup heating.
Rinnai says a consistent approach to predicting SPF could give consultants and building owners a more reliable basis for comparing system designs, energy consumption, running costs and carbon performance. The initiative focuses on predicted performance before installation, rather than subsequent measurement and verification of operating systems.
Industry coalition proposed
The roundtable will involve consultants, engineers, manufacturers, industry bodies, building operators and independent technical specialists. Discussions will focus on the technical requirements of a common methodology, opportunities for independent validation and a roadmap for its development. Rinnai intends to propose an SPF Coalition to continue the work during 2027, with a public report outlining the roundtable’s findings planned for January.
elementalLONDON takes place at Excel London on 25–26 November 2026.
Beyond SCOP: estimating real world heat pump performance with SPF
