HeatpumpMonitor.org next steps

I’ve updated the HeatpumpMonitor.org issue list with a few more items that have been on my mind from recent discussions on here and elsewhere. Feel free to post below with any other ideas that you would like included in future development.

Review the current feature request and issue list here first:

I’ve just added the following items to the list:

  • Make use of the new daily data pipeline with a daily data visualisation tool that allows for e.g the plotting of internal – outside temperature vs space heating demand, with the option to add a line of best fit and projection for space heating demand at design temperature (if no data points exist for this condition already).

  • A: Change the summary page bar graph from a monthly overview to a daily bar graph that replicates the emoncms.org My Heatpump daily bar graph showing electric, heat, outside temperature and COP.

  • B: A second step or perhaps combined with step A is to copy the full MyHeatpump app so that it runs from within HeatpumpMonitor.org. This will enable better privacy control by removing the need to share the MyHeatpump app link with the read api key present in the URL and potentially allow other levels of privacy control e.g the option to disable/enable access to the detailed 10s data at the users will.

  • Add an option for site admin’s to flag systems with data issues and add a comment as to why the flag has been added. This would show up as an icon, e.g red circle with exclamation mark. It would be good to have the option to hide/show systems with data issues.

  • Improve the search / filter feature, some column values are don’t seem to be working with the feature. Explore ways to filter by a stats value e.g flowT<30.

  • Heat pump make & model pages. Try to generate as much as possible via automatic analysis of system data but may require manual selection of e.g minimum modulation examples, maximum capacity tests. Show range of performance seen on real world system for each heat pump type. Collect other useful data such as maximum central heating pump head if this is integrated in the unit.

  • Explore cost implication for each system on different tariffs e.g: user entered unit rate, price cap or average rate and half hourly tariffs: Octopus Agile, Cosy & Go

This is just in the way of mapping out future development at this point, not necessarily making promises on delivery timelines. Im not immediately diving into these either so If anyone fancies getting involved with development and helping with some of this that would be most welcome!

We have also been discussing that it might be useful to find a way to fund some wider work on heatpumpmonitor to enable it to reach it’s potential. If anyone has any ideas on this front please get in touch.

The full list of feature ideas and issues are on the repo, thanks to @Timbones and @glyn.hudson for collating https://github.com/openenergymonitor/heatpumpmonitor.org/issues.


How would I best get involved in development? I am planning to do a proper linear regression analysis on my heat loss data anyways so I might as well contribute that. I would have just gotten the data via the feed api from my local emoncms instance and fed it into some python pipeline but if I can contribute using some different approach I’m happy to do so.


I feel that, in order to increase the value of heatpumpmonitor.org, it’s important to improve the ability to compare systems. However, one of the continued hurdles here is the fact the the total COP includes both heating and DHW and heating:ratio varies a lot based on usage patterns, but also more importantly on property insulation (better fabric means significantly higher % DHW).

I know some steps have been taken to report Heating/DHW separately in the heat pump app, as well as the introduction of the “Heatpump + Fabric” view, but this view has a couple of issues:

  • The COP shown is not the heating COP you’d expect for a “fabric” view, but rather total COP.
  • I assume, although it’s not clear, that the “elec kWh/m²” value includes DHW electricity usage too.
  • This view includes system that don’t differenciate between DHW/Heating.

I’d suggest the following:

  • Document and recommend more widely (include in your kits) DHW diverter valve monitoring.
  • Use two distinct views for heatingand dhw. These views should really only include systems that differenciate DHW/Heating and also include other relevant derived information. (the number of systems that differenciate shoud increase over time if this is promoted and people see their systems aren’t in these dedicated views)
    i) heating/fabric view: heating cop, min/av/max flow temp, kWh/m2, £/m2 etc.
    ii) DHW view: dhw cop, dhw temp, hot water usage, kWh/litre.

(would potentially be good to be able to collapse all the location/installer information when zooming in to look at this data)

Hot water metric could be something like “liters of 40C water per day or week”, and is easy to derive given DHW power.


Hello @Andre_K that sounds really interesting. Perhaps the best first step is to do that analysis on your system using the tools that you are familiar with and post up the results and methodology here and then we can look at how we can adapt it to work on the site?

Thanks @dfeist good ideas. Definitely agree it would be good to do more on splitting DHW and space heating and we need to make that a more standard part of the heat pump monitoring package.


Regarding the DHW, it would be great to have DHW tank temperature and target tank temperature as inputs to the My Heatpump app (similar to the room temperature/target temperature). This would allow a better comparison between systems with different target temperatures. If COP is to be compared between systems at different locations, there should.be a way to normalize to the same outdoor temperature, e.g. COP 7°C, probably also by doing a linear regression on the COP data and then extrapolating. Finally, it would be useful to have an “exclusion time” for the CH COP estimate that not only excludes the DHW runs but also the following short segment of hot water that is going into the heating pipes but was produced during the DHW run, as this can introduce a bias by attributing heat energy to the CH run whereas the electrical energy that was used to produce it was utilized in the DHW run.


A little progress on this, with interesting results, take system 120, a 9kW Daikin with a COP of 2.9 over the last few months: https://dev.heatpumpmonitor.org/daily?id=120

This is not to say over-sizing is always a problem, e.g the 5kW vaillant on the Urban Plumbers system probably has as much excess capacity as system 120 (given how the Vaillants are badged) but is doing very well: https://dev.heatpumpmonitor.org/daily?id=139


What does it look like if you model the 9kW as a 16kW though? :sweat_smile:

Presumably the 9kW should be wonderful at preventing frosting as it has an oversized evaporator?

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It actually has a slightly smaller evaporator.

But to all intents and purposes it is the same heat pump.

The 16kW produces more heat as the fan runs twice as fast on the 16kW.

That is it.

In the same conditions at the same output the performance is near enough identical.

The 9kW is just the 16kW with the fan turned down to limit its output.


Loving this! It would be useful if the x axis didn’t stop at 23° - I have plenty of days below -3°C average and would like to see them as well!


Would be interesting to have an oversize value for all the HP Monitor systems available to graph against COP to see how much of an effect it has on performance.

Although I guess the less oversized systems are likely to have had installers who put more effort into heat loss calcs and will also be the same installers to put more effort into making the actual installation efficient.

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Agreed, I want to create specific info pages on each heatpump make and model and work out a way to pull in datasheet heat pump capacity data into that. Given that the badge does not usually reflect the actual capacity.

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Yes sure, will add that in!

Wouldn’t it be useful if there were an organisation that certified heat pumps; including the capacities at various outdoor/indoor conditions in addition to an estimated sCOP for a particular climate zone; and made that readily available to all and sundry.

You could run it as a nonprofit and call it a certification scheme.

Perhaps it could even fund projects to establish what the heat losses of buildings really were and provide other such design guidance to assist people deploying heat pumps.

Perhaps only give grant funding for heat pumps with true and certified performance figures; installed in line with that sizing guidance?

Naaah. Stupid idea. It’ll never catch on.

Give all the money to a self serving cabal and leave it to the enthusiasts to pick up the pieces afterwards. :roll_eyes:

This is a great piece of work @TrystanLea. I always used to joke that MCS used the heat losses with the ruddy windows open… without realising that this was quite literally true!


it does feel like we’re missing something important in this industry. There’s an opportunity for more of a research and evidence driven rapid feedback loop to design, specification and guidance. The passivhaus institute seem to have been quite successful in this regard in the building fabric space with a successful system for quality control, product certification, high quality design tool etc.

I won’t pretend to know a lot about what goes on in certification bodies, I need to learn more on that topic and we should probably keep this thread to the topic of heatpump monitor development :smile:

Sorry - will keep on topic

I think I replied to the wrong thread too (that was meant for the CO2 thread)

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Work in progress: An improved measured heat demand tool intended for exploring the question of over-sizing and impact or lack thereof on performance (I will do another post on this soon).

  • Work out measured heat loss (or really heat demand as it included DHW demand).
  • Auto fit line of best fit, manually adjust as required
  • New datasheet max heat output for heat pump field available in the main form (I’ve entered all the Vaillant datasheet capacities so far)
  • Hover over datapoints on chart to see more information about each data point.


This tool can be accessed from system view page:


A good example of a high performing Vaillant which is arguably oversized, but without a performance penalty?:


not that it would have made sense to select a smaller vaillant, given that the 3.5 kW unit has the same compressor as the 5kW…


Can Compare button be added to the system page, which automatically selects it, allowing users to add another system to compare to it?

Maybe the Histogram page too.


Maybe once I’ve recovered from the work involved in building the above :joy: