@webcmg Not sure if I have one. Is that the pump attached to the UFH manifold/mixer? 

Your Flow temp is nearly 40ºC which probably explains why you're chewing through 90 Units per day at around 0ºC.

Have you tried lowering your heat curve will bring the flow temp down so your room temperature is comfortable? The key is to warm the house at the lowest flow temperature you can.

My Pumps flow temp has been averaging between 28-34 during this cold spell. 

Are the Heatmisers calling for heat or are they dumb? 

It's in an insulated box inside where the heat pump pipes enter the house. There is a heat exchanger in the box with a pump.

I've tried everything possible with the heat curves to no avail. 

I've turned attention to flow rates and reduced all the pumps on manifolds to a lower flow setting. Will monitor and report back.

I also found this resource for our heat pump which provides lots of additional tech details, which I'll leave here for safe keeping: https://community.openenergymonitor.org/t/vaillant-arotherm-owners-thread/21891

@webcmg Where did you get stuck when trying to use the heat curve? The diagram from the manual shows what the flow temp will be dependent upon the outdoor temp. In my case, 0.35 works well for me. 

@colin heatmeisers are currently set to 30 degrees, so effectively dumb.

Heat curve now set to 0.4 but this is right on the limit of comfort upstairs because rad circuit. I have also reduced all the pumps to their minimum setting. There is also an additional radiator swap pending and some relatively significant insulation improvements and sealing to be undertaken by the developer which might improve this further. 

However, usage is still averaging ~65kwh per day. That's including around 10kwh baseload. Whilst this isn't too bad given the sub zero temps, I can't understand how yours can be so much more efficient, especially given you're in a more isolated location.

What's the construction of your house? Ours is block and beam ground floor with cavity wall insulation. I can only think we must have different levels of insulation and airtightness. I've been using a thermal imaging camera to look at the outside of the property and one thing that did surprise me was the 3 degree delta between the base of the wall and the brickwork above. I've no idea if this is normal for a UFH system that's on 24/7? 

If @mars I think you had a flir camera at some point, did you notice similar with your property? I did this check @ - 4oC so could imagine there could be a noticeable transfer of heat given the 35-40oC flow temps, regardless of insulation.

@colin some monthly updated consumption/yield graphs from Vaillant's app for heating and DHW would be useful to see if you have a sec please. 

Cheers all. 

I'm also trying to get to the bottom of my high running costs. It is arduous to say the least. Have you had an independent inspection @webcmg?

@saz we have 2x 7KWh valliants and over the last 8 days the power for heating and DHW have been around 55 kwh per day. House is long basically single storey 5 bed cottage on east coast of scotland - half 200+Yrs old the rest 30-35 yrs old. Temp for 3/4 of house is between 20-19.5 set from 5.30 to 10pm then setback 17.5 DHW set to 47 on constantly and used for i deep bath a day. Earlier in Dec we were using approx 40kwh for heating and DHW so to calm my nerves i have taken to working on averages which show in a much truer light the cost of the systems. To assist with costs we have installed 8kwh solar ground mounted panels which link into a 9.5 battery. The system is currently useless (2.5-3 kwh a day) but come the summer we generate 35-40 per day so look to being off grid from April to end Sept with good savings mar/apl and Oct/early Nov

@sapper117 Hi. Quick question, slightly off topic but how are your two HPs joined together and controlled? I'm struggling with a dual Daikin system which has no electronic links to each other and just a low loss header to join them.

@sapper117  I don't have any PV panels sadly. I'm trying to find ways of maximising efficiency in the Winter months even though the Summer months should assist the overall yearly COP or 'SCOP'. Your usage appears very reasonable for your property. Mine does not.

@saz look up ripple energy - depends on your age but we decided that it was touch and go as it is unlikely that we would get the full 25 yr return

@chrislay it is all through the valliant control boxes. We have 2 control units and pump 1 is figged as ch pump 2 as DHW and back up to heating which operates quite often in the very cold weather so that we can see pump 1 working at 100% and the most I have seen p2 is at 70% so room onthe system

i only have to set the house temp - we only have 1 zone no fancy valves and work on the valliant external temp system. All the reading I did said that Europe don’t use the thermostatic valves and the system is best left as simple as possible

@webcmg Do not reduce the pumps to minimum setting, it will significantly increase your heating cost. The water transmits the heat, no water = no heat. You are reducing the flow rate and increasing the flow temperature to compensate. High flow temperature = high heating bill. Quite simple really. Turn the pumps up full, then you will be able to move the curve down.

@saz not yet, but suspect it's inevitable given this is a new build and it's not living up to expectations.