You can calculate the COP by dividing the heat energy produced (in kWh) by the amount of electricity used (also in kWh). Hopefully it’ll be 3.5 or more. 

There’s no benefit gained by not heating rarely used rooms, because adjacent warmer rooms would just lose heat to them anyway; also the heat pump works best when there’s a good flow of water around the heating coils. So open up all your thermostats rather than strangle the flow.
Depending on what flow temperature you have (hope it’s on weather dependent control), you will get a higher COP if you can lower your flow temperature while still achieving your target room temperature.

Definitely check HeatGeek.com for some more advice !! 

Thank you for your reply

This is what I have found for November, October and September.

I started to put the heating on at the end of October

Consumed

November 171

October 211

September 119

Delivered 

November 536

October 454 

September 98

This year

Delivered 7587

Consumed 3025

So my cop is quite poor. I imagine it will always be poor when the heating isn’t on though?
It’s a well insulated house with all the insulation being on the outside and rendered afterwards ( was built 2 years ago)

I run the underfloor flow rates  at 2.5 / 2.0 to each 

Hot water is on a timer everyday at 4am - 5am to heat up to 53c

I am on a compensation curve ( have attached a picture of it)

Do you have the heating on a schedule? Is the figure 98 correct for sept delivered ?? Assuming mostly hot water as it was mild that looks like there’s something amiss !

The schedule was set to 23 c between the hours of 4am and 10pm with a drop back of 21c from 10pm to 4am.( On the two rooms I was using )

since your reply I’ve set my thermostats to 28c, so the rooms are always cooling for heat.

the heat pump has never turned off and has been using between 1.5/3kwh on the smart meter. I’ve lowered the curve temp from 35 to  32c to see if it would be cheaper as it’s hot enough.

Sounds expensive!?

Current room temps are 

24 (concrete floor)

24.8 (wood floor)

22.8 (carpet floor)

19.1 (carpet floor)

I’ve double checked the controller and September figures are correct, my Mel cloud app says this for September (attached picture)

I don’t have an Ecodan or underfloor heating! Have you found anything useful on HeatGeek? Particularly for suggestions for flow temp for underfloor heating. I think your looks a bit high at what appears to be 36 degrees on your graph. You said you started the heating at the end of October, but the pie chart says heating was 60% of your energy used in September?

I haven’t found anything clear , I think I might give one of there ‘Geeks’ a call

I did exactly that. I had a suspicion about my Daikin underperforming and got a top geek to come and put it through its paces. He diagnosed the problem - in my case it was something the installer dealt with, but the second opinion was invaluable. You can find your nearest heatgeek on the map on their website.

Hi

Just found this thread and wondered whether Monkswood has been able to find out how to get their ‘delivered’ & ‘consumed’ energies straight from the cylinder rather than the MELCloud app? You need to press the horizontal button on the right and then work through that menu on the right most box. This shows the ‘consumed’ & ‘delivered’ so far for the current month.

Working through the ‘magnifying glass’ icon’ you can get consumed and delivered energies for  the last 2 months and for the year to date to work out the COPs. 

On my MELCLoud app on my tablet & phone I can get bar graphs & piecharts for the ‘consumed’ energy but only bar graphs for ‘delivered’ energy so have to estimate the ‘delivered’ from this bar graph. This correlates reasonably closely with COPs calculated using the values straight from the cylinder considering the former are based on estimations

Btw, looking at your ‘delivered’ chart I make the ‘delivered’ energy 122 (74.6+48.2) not 98

You may also be interested in some data I have gathered.

I live on a new build (4 years old now) estate of 45 dwellings: semis, detached, bungalows; 2, 3, 4 & 5 bedrooms; 4.32kW, 5kW & 8.5kW ASHPs On listening to radio programme on Air Source Heat Pumps where the experts were saying that household should expect COPs of 3-5 if the system was correctly installed, I invited others on the estate to join me in some data collection. 35 householders have been supplying me screenshots of their data for 11 months since Dec 2022. It is surprising how much variation there is for similar houses. Am currently taking it up with the developer.

From all this data, I think the bit most relevant to you might be the summer/winter variations

My observation is the COPs for 4.32 kW heat pumps increased during the summer when no space heating was called for (e.g for one house averaging 1.4 Jan- Apr & 2.7 May- Sep)and only hot water was required. The exact opposite to the larger 8.5kW units (e.g for one house averaging 3.9 Jan-Apr & 2.2 May- Sep).

From the data provided in the post dated 12 Nov I would suggest these findings indicated that Monkswood has the bigger ASHP, 8.5kW?

Incidently, for my 3 bed semi & 8.5kW ASHP, 210 litre tank, UFH downstairs & rads upstairs (heating switched off in Apr & back on in Oct) my monthly COPs are

Dec 22    Jan    Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct 23

   2..1      2.2    2.2     2.1     1.5     1.2      1.1    0.9    1.2     1.1     1.5

I gather from Mitsubishi & other organisations these readings from the cylinder screens & MELCloud are estimates could be10-20% out and that more accurate metering needs to be installed to get more accurate COPs. Btw, an electronics engineer I know has done just that in the last month for his system and found the COP from his more accurate metering to be 2.9 vs 2.4 from the cylinder screen.

Hope this is of help

All good stuff there.. however you are probably quite disappointed with those low COP figures. Can you give a bit more detail of you system? What schedule do you have and what controls etc? It doesn’t really make sense that the hot water cop is better than the heating cop as it’s a function of the increase in temperature you’re asking if the hp so low temp heating should always win over hot water.

I’ve spoken to a heat geek and hopefully he will be coming out soon.

My updated November figures are

Delivered 1186 kwh

Consumed 346 kwh

it does look like you achieve a bad cop when the heating isn’t on much , which might explain the poor results

The main thing I’m struggling with is the zones. If one zone is calling for heat - I ideally need all the zones to be calling for heat at the same time, otherwise I’m wasting energy, as rooms aren’t being used so it’s costing me the same as if they were being used

I almost want all my zones connected to the one stat, so when 1 zone is on it all comes on

The Mitsubishi system is poor at measuring its own consumption at low current draws, I find it is quite variable but averages at 1.5kWh a day, or 500kWh a year – this makes quite a difference to the reported COP values. During the summer when no heating runs my system reports 3kWh a day of ‘heating’ consumption, in reality the system is using 0.5kWh a day to run the FTC board and the MelCloud wifi dongle. It looks worse than it is in reality. The COP for HW will always be lower than the COP for heating as a proportionately larger chunk of its time is spent pushing the flow temps to their highest. This is also a good reason for not running a HW cycle in the coldest part of the day if you can help it (unless its also cheap electric).

The advice about 24/7 refers to not programming on/off periods like most people do with gas CH. Temperature setbacks work a bit like turning a system off as the heat demand will be judged to be satisfied, but having it come back on when the temp drops by 2 degrees, say, allows the system to select the time when to come back on and work not too hard to bring the temp back up.

I think you need to set TRVs properly in rooms that get a lot of solar gain so that they can take themselves out of the heating load, but not just stop the whole heating cycle as other rooms will still need some heat. If you look at the hourly temperature records of the flow and return temps you can see whether you system is supplying heat continually or in short bursts, aka cycling, this will help you aim to set a target flow temperature low enough to keep it going for longer periods.

How do I check my hourly temperature records of the return temps? This seems interesting to see whether it’s cycling (lower cop or heating continually)

@LordHarry any idea?

You have the MelCloud app - it is available in the hourly temperature tab.

should the flow temp and return temp be very similar- overlapping?

If they aren’t, should I be lowering the flow temp?

To give you an update.

An engineer didn’t come out in the end they were too busy , but i managed to raise my cop.

last month it was 3.8 and the start of this month is 4.2.

This is with all the thermostats calling for heat and high enough, so they never achieve the heat so the zone doesn’t shut off .

The heating is set to be on from 4am -9pm

All The rooms of the house are now warmer.

The flow temp is on 30c curve and I’ve manually adjusted the curve.

The cop is better, but I’m not sure it’s better monetary wise

Thanks for popping back with an update @Monkswood! Would be interesting to find out what happens monetary wise.