Energy Stats with heatpump


Really happy with my EmonPi :wink: Have been monitoring my electricity for a while now. Reason was to understand how much energy my GSHP was using. I’m a bit dissapointed in the high levels of energy it’s using - not as green as i was hoping. It’s a 9kw heat pump and attached is the usage for March. Does this look right to you? We are using the Heat Pump for underfloor heating and direct hot water.

Any comments/tips appreciated.


You can compare with my data:

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Many thanks. Great dashboards! I see when my heat pump kicks in i go up to 5000-6000w, but yours seems to only go to around 2900w. I think there must be something wrong and I’m using too much energy to run the GSHP for some reason.

Thanks for sharing. Really useful to see your heat pump status and all the temperatures too. Will compare - but that’ll be a manual process for me as i have no remote monitoring on my Worcester Bosch heat pump I’m afraid ;-(

No, I think this is ok. I use mine only for Underfloor.

When using it for hot water you are leaving it’s efficiency range completely. It’s really a myth that heat pumps designed for underfloor heating temps (Max 40°C) is also able to efficiently heat hot water (up to 60°C) That’s why heat pump boilers are booming here. They have much smaller heat pumps dedicated for doing hot water and are way more efficient than a big heat pump. My father is selling and installing a lot of them lately. They only use around 400-500W to heat the water!

You can compare yours with mine. I have a 11kw heat pump but as said only for underfloor heating and with a 2000l buffer boiler for storing the 32-37°C Water (depending on outside temp). My dashboard is here:
It’s german so Wärmepumpe means heat pump :slight_smile: My hot water is done electrically or with solar panels when there is enough sun power.

That’s good to know. I probably need to look at a better way of getting the hot water. Was thinking of solar anyway, but thanks for the suggestion of a heat pump boiler. Worth looking at.

Your dashboards are what I aspire to :wink:

Hi @Andreas_Messerli
We install a lot of heat pumps (both Air Source and Ground / Lake / River / Water Source) as houses are getting more efficient , the hot water (DHW = Domestic Hot Water) requirement is overtaking the space heating requirement. - We’re UK certified to install them so that our customers can get the government grants, however the UK is still a long way behind the rest of Europe in both adoption and knowledge.

Best installed efficiency is what we are always trying to achieve and always looking for the best options, - the idea of a heat pump dedicated for the DHW may make sense - what make and models is your father installing to heat just the DHW? And what CoP’s does he achieve? one of the things to note is that a 7kW heat pumps will still take 2 + hours to heat a 300 litre DHW tank from cold to 55° as that needs ~14 kWh), thanks.

Hi Gordon

We have a lot of possible options here in Switzerland so the client and his needs like liter volume (100/150/300 liter or more) are the main driver. Most of the DHWs are way above 3,3.

The last one he installed was an Elcotherm Aerotop one. That one has a high COP of A15 (=15°C) 3.4 and A20 (=20°C) 4.0. But as said there are many others. What is a bit annoying is the space they need above the boilers. Sometimes the height of the room is the even more limiting factor when choosing a DHW.
Others he installed were Stiebel Eltron and Swisstherm but I can’t remember which version. Both manufacturers have multiple models in their lineup.

In all the DHWs around here you have just a small heat pump for stabilizing the heat and correct small fluctuations. As soon as there is more heating needed they normally also have a 1,5kw electric heating equipment to speedup the heating process. Still a lot better then my 7kw electric boiler which even needs 3 phases to run. The new ones are just single phase 230V as the auxiliary heating and heat pump together do not exceed 2,5kw. I think this is really nice because people with an average PV installation on the roof can completely profit from this even under the accelerated heating cycle. I think the Stiebel Eltron ones do even have external inputs to actually control them remotely. So you could use emoncms and dump your excess solar power into the heating system and heat it up.

My work colleague did this with his own written logic and an arduino. Whenever the solar system is exporting he actually starte the boiler to heat the water up to 75°C instead of exporting it almost for free to the grid. This way you also do not have to care about the legionella as they die over 60°C. I could you give a list of available DWHs here but I do not know if they are available in the UK.


Hi Andi,

Many thanks for the reply, I think I understand you.

New build houses here often have Mechanical Ventilation with Heat Recovery (MVHR) , there are however appearing on the market a number of Exhaust Air heat pumps directly connected / integrated with a DHW cylinder. e.g. ESP Ecocent, CTC EcoWater, Giona often installed as a Continuous Mechanical Extract Ventilation system.

None are approved for any government support, so that skews peoples requirements. - A single or twin heat pump that does Space Heating and or DHW attracts government support. However exhaust air heat pumps aren’t (yet) supported in this way

All of them appear to offer a better CoP because the air input temperature is (usually) higher than the outdoor ambient, (A15 / A20 as you say) in theory they also offer a greater energy saving advantage than MVHR, however I have yet to do the math as the heated air used by the above DHW cylinder systems are using air from the dwelling heated by another source.

You are correct in that most heat pumps have a built in heating element (auxiliary heater), however we have to design that out of our systems for them to qualify for the government grants, so we are looking for higher efficiency if possible.

There are a couple of off the shelf PV diverter controllers that can switch heat pumps on to heat the DHW cylinder and ensure they don’t cycle to frequently (max 6 times / hour is a top end target) I’ve not looked at seeing if the OEM Solar PV diverter could be configured to do this.

There are lots of products available including the OEM Solar PV diverter that can run the Immersion heater in the DHW cylinder (some are better than others :slight_smile: )- however they are only 100% efficient compared to the 350% efficiency of a heat pump :slight_smile:


Hi Pete

Looking at your consumption, that looks high for 9 kW heat pump - but I’m not sure how your heat pump rates it at 9 kW. I have a 7 kW heat pump (it consumes ~1.7 kW when running). Yours looks like it consumes 5 kW, then I assume it has 4 kW heating element (it would be classified as a ~18 kW heat pump here - 22 kW with the heating element), and it supplies my hot water and heating. But like others here mention, I also have evacuated solar tubes for heating as well. Looking at your usage, it seems off. But that could be because of differing housing standards or house size - my house is +R2000 standard and average size of 120 sq.m - I probably live in an extremely harsher climate compared to you. But say this was an average mild day in March with no sun, and my hot water heating was done solely by the heat pump. I have approximately 300 L thermal buffer reservoir divided between 2 tanks that I heat to ~47 °C. The primary tank is used for domestic hot water and the secondary is for heating. I designed it in such a way that the hottest water from the heat pump siphons into the primary - though i have it set at 47 °C, the hot water tank temp is really 50 °C -ish while the secondary is 47 °C -ish. I would say from the run cycle you probably have your hot water temp set too high, you are circulating at too high of rate, or you are heating a slab that not properly insulated on the bottom side. By comparison in the winter at -10 °C outside, my idle run cycle is once every hour for 7 - 10 min. Your run cycles seem like 15 minutes every 45 minutes. But then again you might be living in a 600 sq.m home, and that would be about the correct heating cycle. If your house is about the approximate size of mine, then look in to properly insulating, with draught barriers would probably reduce your consumption dramatically.

Sorry for the delay in replying…

I have quite a large house, apprx 2600sqFt / 250sqM. It’s a modern house built in 2011 with lots of insulation. We are in the UK and had to build to UK Code For Sustainable Homes level 3 - which is pretty specific on insulation and energy efficiency.

I was a bit concerned about my run cycle. I thought it would have a longer run cycle but less times a day.

I have also been doing more monitoring, and have noticed a very high Heat Transfer Fluid Out value…it’s running at approx 80degC. Is that normal?

Heat transfer fluid in = 15DegC
Heat transfer fluid out = 80DegC

No, that does not sound normal. Like I said, I’m not sure how your specific heat pump works, but generally 80 °C is normally well outside the norms of efficiency (so probably a heating element is coming on). Normally your 3-4 COP is about 50 - 55 °C depending on the heat pump. When running at 70 °C, they are normally ~1 - 1.5 COP. That is big a jump for a heat source - 15 °C in 80°C out; is your pump flow restricted? For my heat pump for example, there is generally a 5-10 °C differential. Yours seems to be a 65 °C differential, that is usually a restricted flow problem and should be popping up error conditions (or perhaps you are reading the gauge wrong). Does your heat pump display ground source temperatures? In general, they should have roughly the same temperature differential. Example: if a ground source is 10 °C in and 5 °C out, then the heat side would have roughly the same 5 °C differential. But I would say your heat pump is not running correctly due to the high temperature differential and probably a restricted flow issue of some kind.

It maybe that I have a faulty temperature probe inside my heat pump, as I also have external temp probes strapped to the flow and return valves just outside of the heat pump. I am monitoring these separately via my emonPi. When the heat pump is operating they show a difference of 3 or 4 degrees, e.g., flow in 12Deg return 8Deg which sounds right.

Will try a ‘heat pump reboot’ and see if that fixes.

If it is a bad probe - I am surprised your heat pump does not throw error condition. Mine does not let it get to 20°C differential, it pops an error condition and shuts down the system. If you can and you feel comfortable, just put an ammeter or emon c.t., right at the compressor. See what it consumes directly. If it is different by lots ( ~ +500W for circulating pumps), then I think you have a heating element kicking on as a lot of heat pumps have booster elements, perhaps it’s that coming on or it is a relay stuck for some reason.

That’s interesting, as I am using way too much energy. I do have an indicator light which is supposed to come on when it’s boosting with the heating element. I haven’t seen that In my observations over the last couple of days, but I’m not near the pump all the time!

Good tip on the ammeter I will try that

Just curious as to how adjustable are your heat pump settings? Or does yours have the common administration lock put on by the installer? Mine is wide open, so I can adjust every setting on the pump. If you are worried about run cycle, maybe you can adjust to get a different run cycle by changing temperature differentials, timing etc. When I first installed my heat pump it was way too sensitive, its run cycle was every 15 minutes for 5 minutes. I kept playing with the setting until I got to where it is now. An idle run cycle of once every hour for ~10 minutes, which boosted my efficiency by 30% on the heat pump due to reduced cycling.

But you know about Rem/rate? Put in your house particulars and your climate, and it will calculate your energy usage pretty accurately - I have used it all the time for last 5 years, it is pretty darn accurate at the end of the day - it is free to use for 30 days or 90 days –

That’s a good point. I think all I can change is the heat curve adjustments. I will see if I can get into the installers settings - saw that in the installation manual this morning

Yes I can! It does say in the manual ‘Your are not allowed to access unless you are a qualified installer’ but I can do the ‘10 second press’ on the menu button and it enables it. So no lock/password.

Already amended the additional immersion settings to see if that stops it coming on, as a test.

Thanks for the tip. There are quite a few settings in there, I’ll need to read the installers manual

Hi Pete
We install heat pumps for a living, and I’m paranoid about configuring them for efficiency.
All manufacturers have different ways and parameters for controlling the heat pump, so if you pop in details of of the make and model of your heat pump I’ll see if I can give you any pointers.
The highest temp output from almost all heat pumps is 65 so if your really getting 80 then the in built immersion (cop) 0.9 is almost certainly running.

Thanks for the offer @Worcester . I’ve got a Worcester Bosch Greenstore installed in 2011. It has a 9kw additional heat unit in it too. It’s the heat fluid out temp that seems to have gone bad! I really think it’s a faulty probe, as it’s now saying between 90-95!

Hi we’re nothing to do with Worcester Bosch :slight_smile:

Back in 2011 it was common / accepted practice to design IN the use of the 9kW immersion heater for temperatures below 2°C to 5°C ti meet the heat load of the property

Based on what appreared to be the poor performance of many installed heatpumps (actually poor design or poor installtion), from 2013 best practice guidelines said that the heatpump should be sized to local design temperatures (-2°C to -5°C) i.e to meet 99% of the heat requirement WITHOUT the inline heater.

From memory the Greenstore is actually re-badged Bosch Thermotechnology AB / IVT heat pump so in Sweden there is a lot more experience with these units than in the UK.

Hope that helps.