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Ground source heat pump is unaffordable to run

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(@gshpwoes)
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Hi - I have joined this forum after a web search as I am looking for some help with why our GSHP is costing us so much money. It was installed a while ago (we've been in the house almost 9 years and the previous owners were the ones to install it a year before that) and we have tried to get to grips with what is going on for a long time, but its now reached a point where electricity prices are so high we may have to leave our house as we cant afford to run it! 

We are a family of 5 and it is a large 5 bedroom house, originally early 1900s building but was extended and upgraded by prev owners. The pump is a vaillant GSHP and we arent on gas network so it heats out hot water too. 

Our house is rarely warmer than 19 degrees unless its a warm summer day. We have underfloor heating downstairs and radiators in the bedrooms upstairs. The living spaces are quite large, but bedrooms are relatively small (cottagey size).

Our electricity usage in December was 2200kwh and I know it is mostly down to the heat pump rather than some electricity guzzling machine left on... We cannot afford this level of usage at the prices we have, especially when we have turned all the thermostats down to ask for no more than 18 degrees. Has anyone got any advise on why our heat pump is so inefficient?

Thanks!


   
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Mars
 Mars
(@editor)
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Sorry to hear about your system.

Could you provide details about the ground source heat pump installation? Specifically, the length and depth of the pipes buried in the ground, and whether it involves a borehole system.

Has the high cost and inefficiency of the GSHP been an ongoing issue since you moved in 9 years ago, or is this a recent problem?

Are you aware if the controls and settings of the GSHP have been set up and calibrated correctly?

Do you have access to any performance data or diagnostics from the heat pump that might help in identifying the issue?

Considering the possibility of inadequate water flow or low water temperature leading to short cycling of the unit, have you observed any signs of this, such as frequent on/off cycles or insufficient heating – are the rads and/or UFH cooler than they were last winter?

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU

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(@gshpwoes)
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thanks for the reply!

I can tell you it is a geotherm 10kW system and the pipes buried in the ground are vertical and supposedly go down approx 100m  - I cant put my hands on the documentation for this at the moment, but we have been told before that the actual pipes should be plenty big enough for the job. 

The inefficiency has been as long as we have had it, and we have upped the insulation in the house and tried to get to grips with the settings better to reduce our usage (we have reduced winter usage by more than 15% since we have lived here), but we had the luxury of RHI payments from many years and the costs being relatively low... but now we have neither.

When we first moved in we were told nothing about the heat pump but after a while we found out about using weather compensation setting (however I'm still not convinced this is set correctly). The problem is that no one wants to look at the system as a whole so we have one person telling us one thing and another something different and we go round in circles, but still using way too much energy and i don't understand it.  

It regularly has problems  - it stops working / breaks down at least once a year often more, and in the recent cold snap we had, it was frustrating as we were cold - the rads in the 2 rooms furthest from the pump were barely warm (and we tried bleeding them), so my kids bedrooms were not getting above 16 deg, but yet the hot water was scalding hot (but we dont have it set to be really hot, so dont understand that either). I think its the hot water heating thats a big issue as our monitor tells me that we use about 25kwh in 8 hours overnight which is when we heat our hot water (and have low level heating). 

I can look at various settings on the pump but dont know what I am looking at, but if you need particular info from it I can probably find it if you tell me what... thanks so much!

 


   
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(@alec-morrow)
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@gshpwoes 

 

what floor coverings? What floor structure? Concrete or in wood? 

heatmiser thermostats.?

Professional installer


   
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(@kev-m)
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@gshpwoes 

scalding hot DHW suggests it's using an immersion heater.  This would use a lot of energy.  Does your GSHP also have a backup heater, i.e. a direct electric booster for the heat pump?

How large is your house in sq metres and what is the heat loss if you know it?  10kW could be on the small side for a large 5 bed 1900 house.  


   
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(@heacol)
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@gshpwoes Cold radiators, you more than likely have a flow problem, unfortunately it sounds like the system is micro-zoned and more than likely has a buffer tank (knowing Valiant). If you are not moving the water, the house will be cold at vast expense.

 

Probably not difficult to get a substantial improvement with 2-3 days work and someone who really knows what they are doing.

Professional heat pump installer: Technical Director Ultimate Renewables Director at Heacol Ltd


   
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(@hughf)
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Budget 8000-1000kWh/ annum, and get that on anything other than the backstop rate and you’ll be about right for a large 5 bed from 1900…

Heck, even on the backstop rate that’s worse case £3k/annum.

What is your historical annual usage in kWh? We’re an end of terrace, on a hill, facing the prevailing south westerlies - 18500kWh of gas and 5000kWh of electric is our average from when we had the gas boiler.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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(@gshpwoes)
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@alec-morrow we have wood floor in kitchen and livingroom and tiled floors in hallway etc downstairs where we have underfloor heating, carpet upstairs in bedrooms where we have rads.


   
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(@gshpwoes)
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@kev-m the v hot water isnt all the time - was just when we had the cold snap - the hot water out the tap was really hot, despite the fact the rads were barely warm. but sometimes its not hot enough... ug. we do have a an immersion that was on the first week we moved in, and our bills were astronomical(even back with low kwh prices!) so i know it is definitely not on now as we switched it off. House is approx 300m2, so it is large, but i know people with much larger houses using a lot less kwh than us...


   
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(@gshpwoes)
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@hughf we are purely electric no gas. our kwh per year was approx 20,000kwh but last year was just over 16,00kwh...


   
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(@gshpwoes)
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@heacol if you can suggest someone who can guarantee a substantial improvement i'd happily pay! i genuinely am at my wits end about it as I just cant believe that we are using so much electricity and i know we are lucky to have a good sized house and it must seem crazy we have let it go on this long, but we have made improvements (double glazed windows that were single glazed, added additional loft insulation, made sure all our lights are LED, when white goods have given up we have replaced with energy efficient ones etc etc) but we really cant afford this.


   
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(@gshpwoes)
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found the details on the bore holes: 2 x40mm diameter 127m deep bore holes.


   
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