Interesting ideas and questions raised by for BetaTeach

Nathan @BetaTeach is asking an interesting question over on Twitter about other ideas and questions engendered by beyond headline COP/SCOP performance, there’s some good suggestions on the replies already, can we think of any other good examples of findings from looking at the data?


In no particular order:

  • grid profiles and aggregation looking at grid electricity demand profiles from the aggregated total electric demand of all heat pumps on HeatpumpMonitor.

  • Vaillant inbuilt monitoring vs MID meters - #51 by Andre_K Vaillant flow and return temperature sensors showing a constant offset even when compressor is off suggesting an offset error that might explain a good part of the variation in performing both higher and lower than parallel MID monitoring. Another example here. Potential for significant improvement in Vaillant monitoring accuracy with factory calibration at relatively low cost?

  • A start on over-sizing vs performance analysis: Exploring measured design heat demand using the HeatpumpMonitor heat demand tool Heat pump oversizing data analysis (not quite heat loss as it’s heat demand including DHW and after gains).

  • It would be good to do more analysis on flow temperature when running vs COP, e.g the 10 highest air source COP’s in January 2024 with 28 or more days of data: Best had an average flow temp when running of 31.4C, highest flow temp of the top 10 = 33.1C. That’s the kind of flow temp you need to average during colder winter months to get COP>4

You can also turn that around and ask what range of COP’s do systems with a average flow temperature when running of 33-34C get during January temperatures (3.6 - 4.0):


Please feel free to list other threads & topics here that might be useful for Nathan, I’ve only been involved in a small subset! @SarahH @Timbones @Zarch @Zapaman any other ideas?

One area where HPM has been particularly useful is when someone comes to the forum and asks about the performance of their own heat pump and being able to compare it to other similar systems. This has helped us figure out when a system is not working as well as its peers, and connect homeowners together to discuss optimum settings and controls.

The Octopus/Daikin threads have been particularly rich in knowledge sharing, discovering things like the backup heaters than can be disabled, and how much better the 8kW is at modulating down compared to the 9kW, plus common gotchas that every owner should check for.

The Histogram and Compare tools on HPM allow comparison of two or more systems, plotting data against flow or outdoor temperature. This allows broad analysis of performance to see the data over a longer period, and factoring out some local variables (e.g. local climate).


Well put, agreed those have been great threads and lots of learning there!

I’d say anothed area we could do more is on operating cost. There’s a huge emphasis on achieving the highest sCoP and sometimes I think that may be at the expense of lowest cost. Getting actual pricing into the system would be a great addition.

In the first year of operation, i focused on getting the best sCoP and achieved around 4.1. This year I’ve run flexibly on Agile - i think my sCoP has reduced to about 3.75, but my annual operating cost, adjusting for wholesale price changes, looks like it’ll be nearly half what it was last year.

There’s huge system value in flexibility so understanding what can be achieved and what consumer benefit can be derived feels important.


As our desired temperature and heat loss are relatively low, the daily COPs have taken a bit of dive with the recent warmer weather. Obviously, I’m happy with how little energy is being consumed by the ASHP but I do worry that someone comparing just COP on without digging deeper might think our installation is underperforming.

Is this where “When Running” versus “Full window” becomes important?

Perhaps there could be a more complex calculation that compares a number of stats to give a better indicator of relative performance. Something that takes heat loss, consumption and ambient temperature into account?

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Thanks @Rachel agreed!

Yes that’s it, and thanks Richard!

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I think as per the twitter conversation the upgrade to HeatPumpMonitor that allows for separate DHW and space heat monitoring has been interesting and probably also will allow more discussions to follow as more systems add this capability to their monitoring set-up.
Separate DHW and Space heat monitoring - Hardware / Heatpump - OpenEnergyMonitor Community

Yes and the histogram and compare tools are and will be very useful

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A post was merged into an existing topic: Separate DHW and Space heat monitoring