Preparing to monitor a new Mitsubishi Ecodan

Newbie to OpenEnergyMonitor and about to have a 14kW Ecodan R32 (PUZ-HWM140VHA) ASHP installed. Do I need to purchase a level 3 monitoring kit to monitor/add my data to or is it possible to extract the data somehow from the Mitsubishi equipment? Also, as we have a cheaper overnight electricity tariff (Intelligent Octopus Go) and cost is as important an outcome as COP, is there software available that will take account of the time of day/unit price when the electricity is used? Thanks for the advice.

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Hello, and welcome to the forum! I’ve split this off as a new topic.

If you want accurate measurements of electrical and heat energy, then you will need a level 3 monitoring kit, either from Open Energy Monitor or Mitsubishi’s own EMP3 kit.

If you only want to monitor flow temperatures and general operation of the heat pump, then Mitsubishi’s “Melcloud” service lets you do that. You’ll need to purchase the wifi dongle for that, which may be included in the package.

If you want to extract data out of Melcloud, you can use pymelcloud or Home Assistant, or I can do that for you.

One can estimate the performance of the heat pump without metering. YMMV.

It’s also possible to talk to the heat pump directly via the CN105 protocol - see this topic for details on how to do that.

There are settings on the main controller for scheduling when hot water runs, and to control the heating. Or you can adjust the heat pump using the integrations described above. There’s also a couple inputs on the main controller for signalling “smart grid”. See topic below for more…


Thanks for your reply @Timbones - I’m completely new to all this so it’s brilliant to have this forum in which to ask questions. Also very much appreciate your offer to help me export data from MelCloud.

Trying to weigh up whether it’s worth spending the extra £800 for metering; don’t want to later regret not fitting it at the time of installation. Could I just check my understanding … is it only that the accuracy of the data is superior from an additional metering system (either from Open Energy Monitor or Mitsubishi’s EMP3 kit) compared to exporting out of MelCloud - or does metering provide some metrics / functionality that would be otherwise unavailable?

If it’s possible to estimate the performance of the heat pump without metering - what advantages draws people to make the extra investment?

Thanks so much for your guidance/advice.

It’s certainly easiest to have the metering fitted when the heat pump is installed, but that’s not to say it can’t be fitted later. Somewhat trickier if glycol is added to the system.

The benefits of O.E.M. bundle is that it gives you accurate, high resolution data, plus out-of-the-box integration into emoncms. Great it you want to be sure the heat pump is working at its best, and so that you can make tweaks to the system to improve it. Anything else is a compromise on ease or data quality.

For example, here are snaphots from three different Ecodan systems that use different meterings: (click to embiggen)

  1. level 3 metering from OEM - data recorded every 10 secs

  2. Mitsubishi metering via Melcloud - data recorded every 2 mins

  3. estimated power via Melcloud - data recorded every 2 mins

It largely depends on what you want out of it. Melcloud data will provide just enough information to know if the heat pump is working as it should, and the estimations of energy will help guide tweaks and adjustments, but not necessarily be comparable to other installations.

It also depends on how much of the integration you want to do yourself, your technical ability and desire to combine with other systems in your house.

The most common heat pump issue I’ve seen discussed is it being oversized for the property, which is something you can only really address before it’s fitted. Pay close attention to the heat loss calculations, especially assumptions about air change rate (ACH), and ask your installer if anything doesn’t seem right.


Getting good data is always worthwhile. As a minimum require the installer to install the pipework in such a way that it can be installed later (straight run available with isolation valves each end).

Estimate how much you would save by being able to improve the COP from 3.0 to 3.5 and weigh that against the cost.

It is likely you will need to spend some of that to simply monitor the data even using the cloud integrations.


5 posts were split to a new topic: Correct sizing of a heat pump


I have sn Ecodan that came with a Sika Vortex flow meter. Ive piggybacked off that with some simple temp sensors and an arduino to get a heat meter which is good enough to monitor performance.


If you are on this site I would imagine that you will be interested enough to want to have the data to monitor and review how your heat pump runs. Of course if you have a heat pump installed and it doesn’t seem to be doing what it is meant to, then that is when having a lot of data will help pinpoint potential issues.
Having a metering package would be the easiest way to get this information unless you are happy to have a new hobby!

I would suggest the minimum you install is an electric meter - the Mitsubishi units seem unable to make accurate energy usage measurements (this a common complaint when people just look at their MelCloud reports) and you need these if you want, as you will, an accurate assessment of efficiency. The pulse output of the meter can be directed to the FTC unit which will then replace its own dodgy estimates in the figures it produces and also passes on to MelCloud. If you are having an EcoDan tank I would also at least ask your installer to plumb in pockets for the flow and return thermistors, as on the pre-plumbed tank they are just surface clips that are very annoying to try to insulate properly, which they need to be.

The basic info visible on MelCloud alone is fine, but the availability of some data is transitory, for example flow and return graphs are only available for 24 hours; hourly temperatures for 2 weeks before reducing to a single datum for each day. When you have a metering package installed (I don’t btw) it is not just increased accuracy you benefit from, I believe you can get more detailed output from MelCloud, including downloading of data as CSV files. This upgraded data may be more completely available for a longer period of time too.

I am, thanks to TimBones, able to see the information at the level of detail shown in example 3, which is based on extracting the data that the unit has uploaded to MelCloud. It is a bit rough but gives a good idea of how the unit behaves as temperature and demand changes. I have then scraped MelCloud in a browser to create a spreadsheet record of energy consumed and generated for 18 months, but that does need a bit of effort to keep up to date.

The other half of the equation is your house heating setup, this is equally responsible for the effectiveness and performance of the heat pump, more so as the setup increases in complexity. Having some basic data such as temperatures at various points from this secondary side might help get a fuller understanding of how the changes that you can make to running parameters in the FTC play out. This takes you more into OEM and HA territory.


I think (others can confirm) if relying on MelCloud you need to be careful it has been connected to the correct metering to get a good level of data from it.
For example the FTC can be connected to the pulse output from an electricity meter.