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What to do if your ground source heat pump costs too much to run

Posted by Jason Hobbins on 8 February 2013 at 10:22 am

Q. Hi wondering if anyone else has had huge problems with a ground source heat pump. Had mine installed when the house was built and have no end of problems......largest and most pressing is the fact that it is costing me around £20 per day to run - which is astronomical and unsustainable! Heat pump provider unwilling or unable to come up with a reason for the huge running costs! HELP!

A. £20 every day to run your ground source heat pump is clearly not sustainable. We were asked to investigate a similar problem someone was having with their ground source heat pump (GSHP) another company had installed.   

To understand exactly when the heat pump was using electricity and how much electricity it was using, we attached some energy monitoring equipment to the circuits that power the heat pump, and monitored the GSHP for several weeks. When we analysed the data we discovered that the electrical consumption was following a specific pattern and was spiking at 6kW. Coincidentally, this particular GSHP had a 6kW immersion heater!  

When talking to the customer we discovered that they had chosen the luxury hot water setting on the immersion heater, which meant that the immersion came on each day to boost the hot water.  

The luxury setting makes the water hotter – a heat pump will heat water to 40 - 45 degrees, by setting it to luxury it will turn on the immersion to boost the temperature to, say, 50 degrees.

The immersion heater in a heat pump is really only there as a backup and comes on when the heat pump is struggling to get the water up to the designated temperature – this may be because it’s too small for the property, or when its particularly cold.

We also discovered that the heat pump that had been installed in this property was undersized, meaning that the internal immersion heater came on several times each day, costing the customer a lot of money to run the heat pump. 

The customer could have saved a lot of money in running costs if the heat pump had been the correct size for the property in the first place and if the luxury hot water setting had been explained to them.

So if you feel you're paying too much in running costs, first check your heat pump settings. It could be as simple as needing to switch them to a more economic setting. If that's not helping, get someone in to monitor the electricity usage, and take a look at the efficiency of the heat pump. It may be that it's too small for your property and therefore having to work extra hard. 

If you’re not sure about how best to use your GSHP, there’s a useful guide on the Energy Saving Trust website. 

Photo: Bryn Pinzgauer

More information:

YouGen guide to heat pumps

About the author: Jason Hobbins is Managing Director of EnergyMyWay

If you have a question about anything in the above blog, please ask it in the comments section below.

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11 comments - read them below or add one

J Smithson

J SmithsonComment left on: 3 December 2015 at 1:22 pm

We have installed GSHP (ground source heat pump) and solar panels into our barn conversion.  This was done all done at the time of conversion, with high levels of insulation.  The ground source utilises pipes running a metre deep under the paddock.  The system has been Fantastic, not only do we not pay anything for heating, we get money back!   The house is cosy, plenty hot water with a log burning fire for extra comfort in the Winter.  We have been in the house for 4 years and have 100% satisfaction for the system.   We live in Scotland, and used Ice Energy.

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Jolyon Welham

Jolyon WelhamComment left on: 26 September 2015 at 12:06 pm

I have a Viessmann Vitocal 200G Ground Source heat pump which  been running for 6.5 years. A fault came up yesterday as follows:

C1-El net/compressor - Compressor Power Supply is NOT O.K. (e.g. Rotational direction, Assymetrical, Phase failure) Compressor Fuse, Main isolator, Phase monitor or motor overload faulty.

Has anybody experienced the same fault? What was the outcome? So far I have been unable to determine where the compressor fuse is - only looking at the installation and service instructions.

Thanks in advance

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Alicia Comment left on: 2 April 2015 at 9:47 am

Hi, we installed a Terra Compact ground source HP eight years ago and have had constant problems and huge electricity bills. Since December it's a choice between hot water for 3 teenagers or heat downstairs. An engineer has been 3 times, topped up gas, changed overflow tank and looked at settings. I'm tired of it. Does anyone have any ideas on the best way to change this system? Cost is an issue as is distance, I'm away up in the Highlands. I don't really want to go to oil but I can't take the noise, the cost and the unreliability of it. Thanks for any advise. 

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Graham Marshall

Graham MarshallComment left on: 25 March 2015 at 1:35 pm

Sadly,  am not at all surprised by these horror stories. My wife and I have been searching for an old house to live in for some months. We plan to spend a couple of decades at least living there and are well aware, from experience, of the problems we are likely to encounter keeping the building comfortable. Consequently, during our search for a property I have been researching the various forms of energy production available and how they may be utilised. There is a huge amount of information available on the internet but it is not necessaily easy to access and often incomprehensible, misleading or both.

Recognising that the first thing to do is discover how much energy we need I turned to the EPC and that's where I discovered the first major problem. Few people seem to understand the information produced by the EPC, fewer still how it is calculated and even fewer the flaws in the system.

For example: I understand the EPC uses average values for the U-value of walls. I am considering a property which has solid sandstone walls which vary between 300mm and 900mm, a loft with part of the floor over a pend and a room with an uninsulated timber-frame external wall. All of these have a potentially dramatic effect n the energy use of the building yet the EPC recommendation is to add 50mm of either internal or external insulation, presumably to all walls.

It seems logical to me that the amount of insulation required to insulate a 900mm wall externally must be greater than that required to insulate internally -  one is heating the wall as well as the room with external insulation. In addition the U-value of a 600mm sandstone wall is between 1.5 and .6 while the U-value of a 300mm sandstone wall is about 2.3. The implication of this is that any system designed using standard values is likely to be wrongly sized.

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westertonComment left on: 17 March 2015 at 9:42 am


Reading the feedback and comments, I now wish I had never even considered a GSHP. It has been a fiasco from the start and its not even finished yet.

Two bore holes at £10,000, (now told should be four) "APPROVED" installer came to connect the house to the bore holes, damaged a field drian (still flooding and damaging my drive 7 months later) damaged the main water supply as well.

I was told by the installer the conection pipes to the bore holes needed to be 1.2 metres down, beded in sand, and they would come in under the floor of the new plant room (this had to be created once i found that the tanks would not fit in the utilityroom as agreed) so I lost a room of my home to the "plant room"

When the peipes were being fitted I asked why they were only 60cm down, and in very rough earth, I kept being told they will be fine.

After months of reasearch, and contacting teh GSHPA (who were little help) I got the regulations, and found out the pipes had not been installed as per the regulations, 

Once I challenged the contractor, he blamed the bore hole company (which he arranged and ordered) blamed me, blamed the digger until he decided he no longer wanted to do the job, The contractor had my deposit, but did offer to refund it.

I made a complaint to RECC, GSHPA and Napit etc (no sign of MCS when you need them) months later, with still not heating or hot water Napit agreed the work was not as per the regulations, but said the contractor was willing to complete the instalation!!! Attempted to arrange a meeting with the conctractor, but just gave the run around, went back to Napit, who then anounced they were passing the complaint to RECC!!

RECC have trouble even reading let alone replying to e mails, so now I have had to go back to Trustmark and am awaiting them to meet RECC,CAB, and my MP have all been involved.

Energy saving trust were no help and as with all the above mentioned they just passit on, no one deals with the problem, meanwhile I have no heating or hot water.


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mikeambroseComment left on: 27 February 2015 at 5:52 pm

Well I saw these posts and thought I could help but I've just realised most of them are from 2013 if there is someone with a current problem please repost as I've got a timer keeps coming up on the screen trying to log me out . A heat pump is the most efficient way you can heat your house but it needs to be set up properly if you put the model of the heat pump in your post I might be able to help with the settings

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swilsonComment left on: 19 January 2015 at 2:37 pm



I came across this website on google as am desperately looking for answers to why our heat pump is using so much electricity.

We moved into our house the week before Christmas, just over a month ago, which has a ground source heat pump, which was installed by an MCS installer in 2011.

The house is a large house (5 bedrooms, 3 reception rooms), it is old but was extensively refurbished at the time of installing the heat pump. We haven’t had a bill sent to us yet, but I am terrified about what it will be as in the 5 weeks since we moved in, we have used a staggering 4400kwh of electricity… This is totally unsustainable and unaffordable, and what is frightening is that despite this we are often cold particularly in the evenings and we have double checked some rooms with separate room thermometers and we are never getting above 17deg in most rooms even during the warmer parts of the day. We have had an engineer from the pump manufacturer come out to look at stuff and he has made some tweaks last week, but in checking our meter readings we are still using so much electricity for so little heat. I see from the blog above that this could be from the system being undersized - what can we do if it is undersized, where do we go from here? I assume we can’t make it bigger? I’d be v grateful if you can advise on what possible ways we can improve this situation, as we are currently very worried about the bills being SO much despite the previous owner saying bills were much less that this level of electricity usage would imply.


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NicoleYouGenComment left on: 14 March 2013 at 1:00 pm

Hi, Rob, that doesn't sound fun! I'm really sorry to hear that. It's possible that one of our energy experts might have some insight, I will see. Best of luck with that.

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Bob hook

Bob hookComment left on: 14 March 2013 at 10:17 am

can anyone help me, I moved into a new house Dec 2012 and it has Worcester heat recovery system, it has two 120meter deep boreholes, the house just does not get up to temperature, all underfloor heating, early Jan I complained to the guy who installed it and he came and activated the imersion heater.  in 3 weeks I ran up £800 bill so it was sitched off but now we cant get 15 degc and its cold, the engineer has isolated 3 rooms that are not being used and its made no difference, he is a really nice guy and has even got worcester out but they are scratching their heads and have no idea what is wrong.  they have bleed the system and got a little air out and that made no difference, its costs about £18 a day, the hot water is good and hot help please

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John Barker-Brown

John Barker-Brown from Kensa Heat PumpsComment left on: 21 February 2013 at 10:40 am

Unlike fossil fuel boilers, heat pumps are unforgiving when it comes to sizing. With a fossil fuel boiler increasing the size to add a safety factor is generally acceptable. The cost between a 20kW or 30kW boiler is not large. However increasing the size of a ground source heat pump can have a marked effect on the cost and cause issues with cycling of the heat pump. Fitting a smaller heat pump also has an effect as the heat pump runs harder, relies on in-built expensive immersion heaters and ultimately could cause the ground to freeze.

Some key points to remember when looking at any heat pump ground source or air source are:-

Sizing – Sizing of the heat pump should now follow MCS guidelines. This means the heat pump needs to be sized for 100% of the heating load without the use of in-built immersion heaters. Immersion heaters are allowed but only when the heat pump needs to go outside of its design conditions. The more immersion heaters are used the higher the running costs as you are paying for direct electricity. Heat loss calculations should be completed to provide information on the heat pump peak heat load and annual load which will be used to size the ground arrays.

Heat emitters – Heat emitters should be sized for the lowest possible flow temperatures. Any heat pump works more efficiently the lower the required outlet temperature. For example underfloor in screed generally requires a flow temperature of around 35C, where as radiators require 45-50C. Even this 10 to 15C rise in outlet temperature can result in a 25% drop in efficiency. Remember if underfloor is used, a higher flow temperature might still be required if wooden floors or thick carpets/rugs are placed over the underfloor pipes.

Insulation – If the insulation of the property is not as expected then the sizing of the heat pump calculated will be wrong. This might mean that the heat pump (in order to keep the building warm) has to run at a higher flow temperature or run the internal immersion heaters which as mentioned above reduces efficiency. In extreme cases the heat pump at maximum output might not be able to produce enough heat to actually keep the building warm.

Control strategy and installation – The control strategy and installation needs to be completed to maximise the use of the heat pump and minimise the use of any immersion heaters. DHW production needs to the timed to suit the end user while providing the most efficient use of the heat pump. Again to produce DHW the heat pump needs to run at a higher temperature reducing the efficiency of the heat pump.

It is also worthwhile checking to ensure that any high electricity bills are actually attributable to the heat pump. This might seem obvious but fitting a lifestyle choice of an electric range style cooker can be overlooked as a high usage of electricity with the additional cost being allocated to the heat pump.

With the introduction of the MCS guidelines, issues with sizing and installation should now be avoided, leading to installations having the best possible running costs. However with the Government dragging their heels regarding the RHI and the additional costs of complying with the MCS guidelines we are now seeing the development of a two tier market – MCS approved installations and non-MCS approved installations. A dangerous situation and one which could dent customer perception of heat pump technology.

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Bob Irving

Bob IrvingComment left on: 8 February 2013 at 10:48 am

Some heat pumps - IVT, for one - have a "pasteurisation" facility which runs once/week to boost the DHW temperature to 60 deg C to avoid legionella. Most people turn this off a) to save electricity b) to avoid being hit by over-heated water in the shower on the morning of the night when the process happens. 

GSHPs with weather compensation also tend to run their heat circulation pumps almost continuously, apart from when external temperature rises above, say, 16 deg C. I've thought that this could be set lower to save electricity as I can't see a disadvantage.

I could imagine that 'lumpiness' in heat pump ratings could give the opposite type of problem to that in this piece - poor efficiency due to frequent cycling of the compressor - if the next size up of system was installed.  

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