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MCS certificate SCOP vs real-world performance

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Last Post by JamesPa 3 months ago

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Mars

(@editor)

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Topic starter 18/09/2025 12:10 pm

Every MCS-accredited installation comes with a certificate that includes a headline SCOP figure for your system. On paper, this is meant to give an indication of efficiency, but as we all know, real-world performance can often be quite different.

I’m really interested to get a sense of how these figures stack up in practice. Could you please share the SCOP figure listed on your certificate and how that compares with your actual performance (seasonal COP, monitoring data, etc.)?

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JamesPa

(@jamespa)

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18/09/2025 1:04 pm

MCS:3.65 Reported by Vaillant: 3.96 (heating only); 3.89 (heating plus DHW). Vaillant 7kW, radiators, FT 44@-2, room temp ~20.5, open loop, no buffer.

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Old_Scientist

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18/09/2025 5:58 pm

MCS SCOP 3.84 (design LWT of 47C)

Actual real world SCOP 3.75 (running LWTs of 32-35C)

So despite running significantly lower LWTs, real world SCOP is still lower than the MCS figure.

Samsung 12kW ASHP, large radiators (LWT 35C@-2C), open loop with 50L volumiser, room temp 20C

I'm not sure how accurate the Samsung data is, as reported usage is higher than recorded by my MID-approved meter, which only measures the ASHP and does not include the circulation pumps. Using the MID meter readings (excluding pumps), I get a SCOP of 4.19 which gives a more direct comparison to the old oil boiler which used even more electricity having oil and circulation pumps.

This year we have added the battery, so will be running more continuously than last winter where we ran some fairly extreme set backs to time shift on Cosy. This should see our SCOP improve so it will be interesting to look at the data next spring for a direct comparison of two very different ways of running and how they compare (all else being equal in the house)

This post was modified 3 months ago by Old_Scientist

Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.

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JamesPa

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18/09/2025 9:19 pm

Posted by: @old_scientist

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Samsung 12kW ASHP, ... 1600l kerosene pa

That may be contributing to lower than expected SCOP. 1600l=16MWh =very roughly 6kW loss assuming you were previously heating your house. Running continuously may help less than expected, in fact you may benefit from running in batches. Overestimate of loss would also account for being able to run at a lower FT than design

This post was modified 3 months ago 2 times by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

👍

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