As commercial buildings transition away from fossil fuels, professionals across the construction and building services sectors face increasing pressure to deliver efficient, regulation-compliant systems. Whether you’re an M&E contractor, a specifier, or a building services engineer, understanding the difference between COP (Coefficient of Performance) and SCOP (Seasonal Coefficient of Performance) is essential to selecting, designing, and integrating heat pump and electric heating technologies.
In this comprehensive guide, we explain what COP and SCOP mean, how they differ, and why SCOP is the gold standard for real-world system performance across ASHP (Air Source Heat Pump), WWHP (Water-to-Water Heat Pump), solar thermal, and electric water heating solutions.
What is COP?
COP is a snapshot measure of a heat pump’s efficiency under ideal laboratory conditions—typically at 7°C outdoor air temperature and 35°C water output. – For example, a COP of 3.5 means the system produces 3.5 units of heat for every 1 unit of electricity consumed. – COP is measured according to EN 14511 and is useful for comparing like-for-like products, but it does not reflect how systems perform in real buildings over time.
What is SCOP?
SCOP is a seasonal average efficiency based on varying outdoor temperatures, part-load performance, defrost cycles, and auxiliary energy usage. – It’s calculated according to EN 14825 and gives a much more accurate view of a system’s year-round performance. – SCOP is the benchmark for compliance modelling, funding applications, and hybrid system integration.
Why SCOP Matters Across Disciplines
For M&E Contractors:
Right-sizing Equipment: COP-based sizing often leads to oversized systems that short cycle and wear out faster.
Integration: SCOP enables better performance planning when combining technologies like ASHP with electric water heaters and solar thermal.
Compliance: SCOP data is often required for Building Regulations Part L, the Public Sector Decarbonisation Scheme (PSDS), and client reporting.
For Specifiers:
Reliable Modelling: SCOP ensures that designs meet performance targets under real-life operating conditions.
Comparative Analysis: Helps select the most efficient combinations in hybrid systems, such as WWHPs and solar thermal setups. –
Funding Justification: SCOP-backed designs provide solid foundations for securing grants and meeting sustainability KPIs.
For Building Services Engineers:
Technical Design: SCOP allows for precision in system simulations using tools like IESVE, TAS, or TM54 assessments.
Performance Assurance: Engineers can validate expected outcomes by referencing SCOP values at relevant flow temperatures.
Lifecycle Planning: SCOP helps balance capital cost vs seasonal efficiency for best long-term value.
Real-World Case Studies
Office Retrofit Example: – Project: 4-storey commercial office retrofit using ASHP and solar thermal. – Initial sizing was based on COP = 3.5. In-use SCOP measured at 2.9 due to winter defrost cycles. – After integrating buffer tanks and lowering flow temperature, SCOP improved to 3.3.
Leisure Centre Upgrade: – Technology: WWHP + solar thermal for space heating and DHW. – Original COP: 4.8; Actual SCOP: 3.6 due to uninsulated pipework and constant-speed pumps. – After upgrades (pipe insulation, variable-speed drives, weather compensation): SCOP improved to 4.2.
Best Practices for All Stakeholders
- Request SCOP Data Across Flow Temperatures: For example, WWHP might deliver SCOP of 4.0 at 45°C but only 2.7 at 70°C.
- Design for Flow Temperature: Match emitters and pipework to maintain efficient temperatures.
- Include Defrost and Auxiliary Loads: Pumps, controls, and defrost cycles can impact SCOP by up to 20%.
- Use SCOP for LCC and ROI: Life Cycle Cost analysis and payback calculations should be based on seasonal performance, not ideal lab tests.
- Integrate Monitoring: Use BMS to track in-use performance and compare against SCOP expectations.
Technology Performance Comparison Table:
| Tech Type | COP | SCOP | Flow Temp |
| ASHP | 3.8 | 3.2 | 35°C |
| WWHP | 4.5 | 3.9 | 35°C |
| Electric WH | 1.0 | 1.0 | 60°C |
| Solar Thermal | N/A | N/A | 60°C |
Whether you’re selecting components, designing entire systems, or ensuring regulatory compliance, SCOP must replace COP as your guiding metric. Unlike COP, SCOP accounts for the complexities of real buildings and gives all stakeholders—from contractors to consultants—the insight they need to deliver efficient, future-proof heating systems.
Prioritising SCOP in system selection and specification is the fastest way to hit carbon targets, reduce operating costs, and futureproof your decarbonisation projects.
Further Learning
Consider joining one of our live, online CPDs. Our CPD on Heat Pumps for Commercial Heating and Hot Water Applications has been updated for 2025. It’s CIBSE approved and covers COP and SCOP in more detail. All attendees will receive a certificate for their training records. These are usually sent out 24 hours after completed attendance. To view the schedule please follow the link to our CPD page.