How are your heat pumps wired up? Two single phase circuits or a single three phase? The OEM kit can monitor multiple electricity meters, at 45 amp per single phase and 100 amp three phase. 

Even large pumps can be on 16 amps single phase, so the thought of installing a smart socket or switch that can measure energy comes to mind.. 😉 

May need to inform your pump installer.. 

Then you just get that info via the app.

Or then move to a home assistant setup taking the sensor feeds and just let it do all the calculations for you.. 

but it is in theory a condition of the BUS grant that we monitor our usage and efficiency.  Not really that easy to do!

ps must change profile picture. Makes the house look cold - but it really isn’t!

Did you ever resolve the energy monitoring for your cascade system as I have the same issue with a rencent install?

Thanks. Caroline 

should the functionality to measure my usage have been provided by the installer as a condition of the MCS accreditation? Or do I now have to pay more for it?

That's really a question for the OpenEnergyMonitor folk (hello@openenergymonitor.zendesk.com) but if you just wanted to monitor the combined input/output then it seems likely. If you could fit the flow meter and temperature probes in pipework where the water to/from your two heat pumps is combined then it would look like just one heat pump to the sensors. How are your heat pumps wired up? Two single phase circuits or a single three phase? The OEM kit can monitor multiple electricity meters, at 45 amp per single phase and 100 amp three phase. 

but as Jan and feb have been unusually cold this year I am finding the electric usage very high - (I suspect that had we still been on LPG that usage too would have been very high) but I don’t yet know the efficiency I am getting out of the system. I am running pure weather compensation trying to keep downstairs at 19 or 20 degrees and upstairs a couple of degrees cooler. (All TRVs open, and all room stats set above these temperatures) 

i am acutely aware that I am unable at present (should ofgem ask - which is their right under the terms of the BUS grant) to measure my energy usage because the MELCloud cannot compute energy usage for cascade systems. Can anyone help here please? Does anyone else have this issue? 

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Do you know if the outside unit has a heat meter?  On OpenEnergyMonitor they all seem to be fitting heat meters to their systems so I thought maybe the "heat produced" was just an estimate rather than a measured quantity.

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Sadly I don't know, but would be interested to know since I have a Mitsi myself. Nor, like you, do I know the detail of what a heat meter is actually measuring or the specifics of how it does it.

Mitsubishi's use a Sika flow meter and two thermistors (attached to the outside of the flow and return pipes) in the "plant room". From those the flow rate and dT can be determined (SUNandAir's post describes why these are important). In comparison to OpenEnergyMonitor kit, the flow meter is also a class 2 device but the thermistors attached externally are far less accurate (OEM uses digital temp probes in the water), so OEM kit will be able to more accurately calculate the heat/power produced. In addition, the OEM kit uses a class 1 electricity meter to measure electrical input - I don't know what Mitsubishi use for their COP "estimates". 

Having a Mitsubishi with both Mitsubishi's and OpenEnergyMonitor monitoring, Mitsubishi/MELCloud gives a rough idea of what is happening but OEM is more accurate and gives far more detail.