The honest verdict on the efficiency and sustainability of air source heat pumps in the UK

by Mars
renewable energy heat source

When we committed to installing an air source heat pump (ASHP), we had reservations whether it would heat the house sufficiently. At the same time, we wanted to move away from oil so that we could be more sustainable and reduce our carbon footprint. So we took the plunge.

There are a lot of naysayers when it comes to air source heat pumps. Most say that they’re not good enough to heat homes in the UK over winter because it’s too cold and wet.

Throughout spring and autumn, our ASHP operating costs were much cheaper than oil. The real test was always going to be the winter when there was less heat in the air and where the pump has to work harder.

Luckily for our review, we had an awful December and January that was cold and damp; the worst weather conditions for ASHPs to operate in.

In the video below, we provide an honest verdict on whether we think that ASHPs are effective, efficient and sustainable in the United Kingdom.

It’s obviously worth noting that each air source heat pump is different. We have an 18kW unit from Global Energy Systems, a British manufactured pump, and results may vary from the size of your pump to the make/brand. We have not had an air source heat pump before, so we have no point of reference.

In fact, if you have an air source heat pump in the UK, I’d be very interested to hear your thoughts and feedback, and how it compares to ours, so please leave a comment below.

Consumption highs and lows of our air source heat pump

January 16, 2020, was our warmest day by average at 7.4C over the course of the winter. The coldest was January 20, 2020, at 3C. Relative humidity throughout January hovered at the 40% mark.

On January 16, 2020, we used 53.2kWh electricity (95% for central heating and 5% for hot water) to drive our air source heat pump.

By comparison, on January 20, 2020, the colder day, we used 66.6kWh (95% for central heating, and 5% for hot water).

So we used an extra 13.4kWh to heat our house when it was approximately 3.4C cooler outside. This is not insignificant from a running cost perspective over a long cold spells. The financial costs will add up. If you are going to solely use electricity to drive your central heating, that is some interesting data right there.

But that doesn’t tell the full story if you’ve got a solar PV array. The reason why it was warmer on January 16 was because it was overcast and rainy. So we produced virtually no solar (it was less than half a kilowatt hour) but the clouds didn’t allow the heat to escape.

air source heat pump ideal with weather with solar PV
January 20 was bright and fresh

January 20, however, was a lot sunnier and our solar PV produced 18kWh of electricity – we had to buy in 70kWh. On January 16, we had to buy in all our electricity as we produced close to zero, which was over 80kWh.

DateASHPSolar PVAverage Temp
Jan 16, 202052.3kWh07.4C
Jan 20, 202066.6kWh18kWh3C

It therefore appears that with solar PV assistance, cold bright days are better suited for ASHPs, because they go a long way to offsetting electricity consumption.

If you’ve got an air source heat pump without solar you’re probably better off with more gloomy, overcast warmer days and nights that trap the heat because they’ll run are efficiently. At least that’s what our data is showing us at the moment for our pump and weather conditions.

It’s just an observation at this point, but over the course of the coming year I will look into this more closely and determine whether this correlation is accurate and precise.

EXCLUSIVE OFFER

If you’re interested in an air source heat pump from Global Energy Systems, you can use this code when you contact them and you’ll get £200 off your installation (and we’ll get some Amazon vouchers): GESRFAF000160

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2 years ago

[…] UPDATE Feb 19, 2020: the winter review is available here. […]

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2 years ago

[…] There are skeptics as to whether ASHPs can be effective in the UK. Check out our winter air source heat pump review. […]

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2 years ago

[…] It’s been a year since the panels have gone up, and they have met our expectations. Our primary reason for installing a 6.16kW array was so that it could contribute towards the running costs our air source heat pump. […]

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2 years ago

[…] we have managed to get renewable forms of heating (air source heat pump) and electricity (solar PV array), our next big projects for this year are going to be getting our […]

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1 year ago

[…] Another massive difference between the ASHP and the oil boiler is that with the ASHP our heating in the cold months runs 24/7 versus limited timings on oil. We’ve covered this aspect before. […]

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1 year ago

[…] on the path to sustainability with renewable heating, solar PV and our new veg patch, the weather has never been more important to us, so we’re very […]

J Guenther
1 year ago

Interesting.

John
John
Reply to  J Guenther
1 year ago

Hi,
I watched your video with interest.
We have just built a house with underfloor heating and an air source heat pump. We moved in pre Xmas and the system has been struggling to get the house up to our target temp of 20/21 degrees.
There are three open fires and the “building regs” incoming air vents next to the fires which have been blamed for the systems performance. We have therefore blocked the chimneys and the vents.
Annoyingly the system still struggles to get the house up to tempreture when the outside air temp goes below 2 degrees and certainly below freezing.
In reality do houses with airsource systems need a secondary heating system in very cold weather? We have been told putting log burners in the three fires places would solve the problem and give us a secondary booster heat source in extreme weather.
I would welcome your thoughts.
With thanks
John

Susan+Fawn
Susan+Fawn
Reply to  Mars
1 year ago

Hi we are now 2 months in to experiencing ASHP in our new build. (Underfloor ground and rads on first floor.) Initially we were a bit alarmed at the consumption of electricity but daily monitoring shows on milder days we use as little as 30kw with highest 69kwwhen it was minus 4 overnight. The house is being maintained at a comfortable 20/21 (it us 228 sq m). Our Grant Aerona system is 11kw.
If anything it is too warm upstairs overnight.
The aspect of the house is South at front so on sunny days front rooms naturally rise to 24 degrees in winter.

Overall our bills will be higher than normal mains gas/elec CH ystems but hopefully claiming the RHI grant will off set this for next 7yrs.

I would be interested in other ASHP users experience of annual maintenance costs/ advice of the system going forward. Do you think a maintenance contract is essential?
Sue

Edwin D Faulkner
Edwin D Faulkner
Reply to  Mars
1 year ago

Hi, Interesting to see your experience . We have had a Ground source heat pump system for 10 years but the ground loop has developed a leak, the rate of which varies from top up every 3 weeks , to similar volume in 5 days. As regards performance the house has been kept at 20 C and the hot water at 48 C for the 10 years, the only issue was a 60 hour power cut due to severe snow fall wrecking the local distribution. Like you previously we had oil fired boiler which consumed >2000litres of oil and was on timer control. So we are considering changing to an air source . Your system is much larger than we are being recommended and I wondered what volume you were heating and are you like us just 2 people in the house 24/7. With the GSHP we installed cavity wall insulation and lots in the loft and it is a 7 kw system.

Alistair parkin
Alistair parkin
Reply to  Mars
1 year ago

Sorry to hear this, it is not encouraging, for the millions of Victorian houses a and 30 and 40s houses. Seems it would involve expensive renovations. Electric boilers or even storage heaters sound a better option.

Julian M
Julian M
Reply to  Alistair parkin
6 months ago

Electric boilers are not a sensible option for anyone, they have a CoP of just under one at all times so would cost far more to run than an air source even in cold weather, they are about 3 times as expensive as gas boilers to run.

Geoff Harvey
Geoff Harvey
Reply to  John
1 year ago

We had a LG ThermaV split installed and I just could not understand why, when the temperature was way below target (say 16.5 versus 19 set) the HP was just taking it easy. When set to 19 continuously it coped with even the coldest weather but if we tried to have it at 18 during the night, it would take up to 24 hours to recover the temperature back to 19. But I think there is some strange interaction with the Honeywell wireless stat (which uses a sort of pulse modulation near to the set temperature). I eventually set up the Honeywell to pulse to 20 deg for one hour in the morning to spur it up into action after the 18 deg night time spell, and now it works fine. So what appeared to be lack of heat output turned out to a control problem that I still have not understood

bung
bung
Reply to  Geoff Harvey
7 months ago

Ideally you should not use a room stat at all, but instead setup weather compensation curve. i am not an expert but i think this uses the outside temperature to control your heat pump, kind of preemptively, rather than waiting for the outside weather to affect your room temp, and in tern your room stat.

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1 year ago

[…] If you’d like more information on air source heat pump electricity consumption on cold sunny days versus warm overcast days during the winter you’ll find this post interesting. […]

Mark Rosher
1 year ago

This post reminded me of the heat pump I built from an old fridge, back in 1975, for my school physics project. Powered by a vertical axis wind turbine on the roof of the science block made from a halved chemical barrel and a car alternator, it warmed the science block in winter and cooled it in summer – after a fashion.

It would help to understand how large your house is and where. Maybe that’s back in the blog somewhere (I’ve not looked, sorry). I checked and my average daily (gas) heating and electricity in January 2020 was 65kWh (4 bed detached, 4kWp solar, UK west country). I have a larger than average electricity demand (my bad).

George Applegate
Reply to  Mars
1 year ago

Good news by your knowledge of this heat pump installation.

Alison Gray
Alison Gray
Reply to  Mark Rosher
1 year ago

I have a Grant Aerona installed into my new build house. In the summer it’s fine, but that more to do with the fact the system doesn’t ever have to switch the underfloor heating on because the fact the house is south facing and Mother Nature heats the house for free. So it only has to heat the hot water, which, in the warmer months, it does very successfully.

In the winter on the other hand, when the temps drop to 3degrees or below, it’s absolutely appalling. It struggles to heat the house to anything over 17degrees Celsius and hot water? Forget it.

If you live somewhere that’s 20 degrees outside all year round, great. If you live in the UK, don’t install one. They’re terrible. Having spoken to 3 other residents in the estate, all 3 houses haven’t had hot water now for 3 days. Living the dream. If I could have it ripped out and have a combo boiler installed, I’d do it in a heartbeat. The site manager is going to have a lot of cold, smelly and angry people in the site office on Monday when they return after Xmas!

Samantha Waby
Samantha Waby
Reply to  Alison Gray
1 year ago

Hi Alison, I found your comments very interesting, if a little depressing as I’d hoped that it was just my system that was faulty, and could, therefore, be fixed.

Your problems absolutely resonate with me as the minute the temperature drops, our system becomes useless – yet incredibly expensive. We have an LG pump with underfloor heating, and, like you, I long for a gas boiler or to simply be able to walk away from our “dream”, very expensive home.

I don’t want Home Farm’s website to become anti ASHP as that’s not their aim, but if you did wish to discuss this further I’m happy for them to pass on my email so we can exchange ideas and suggestions.

You have my absolute sympathy, and I feel awareness of how ineffective these systems are needs to be highlighted whilst the gov’t throws financial incentives at them.

Regards
Sam.

Samantha waby
Samantha waby
Reply to  Mars
1 year ago

Thank you Mars, as always that is very kind of you. I understand and appreciate that you are happy to highlight ASHPs, warts and all, but simply don’t want to hijack your passion for sustainable living, as I too, am (was) passionate about living a “greener”, gentler lifestyle. But thank you for your open attitude. Sam.

Danny
Danny
Reply to  Mars
1 year ago

Hello, I have Daikin ASHP which runs my hot water and underfloor heating. End of last year I had the unit serviced and gas changed and during the last few months the heating doesn’t heat up above 19degrees during the cold periods.

Somebody mentioned to me that If the gas was not correctly removed (mode 21) the system could have to much refrigerator gas and could be the issue why the underfloor heating is not heating sufficiently.

Has anybody heard of this as possible issue?

Hot water heats fine.

Peter
Peter
Reply to  Samantha Waby
10 months ago

I am just having a Samsung unit installed but have insisted on the oil boiler being left in place. I have also asked the installer to program so the hot water is on oil and the system switches from air source to oil at 5 deg outside temp. Is 5 Deg a good balance or should that be slightly higher or slightly lower. Looking for best balance between cost of heating and having enough heat to keep the house warm. Pre Airsource we run the house at 18.5 most of the time and 19.5 in the evenings with no heat from 10pm to 5:30 am

Jill
Jill
Reply to  Samantha Waby
6 months ago

I have just been reading comments on ASHP’s. We have had one for the last 7 years. During the winter it has been a terrible experience. First of all it favours heating the hot water so whilst doing that the central heating goes off. By the time it returns to the central heating the temperature of the house has dropped dramatically and the pump really struggles to heat the house satisfactorily. We have underfloor heating downstairs, smart rads upstairs + solar panels. The ASHP broke down three weeks ago, the manufacturer is totally disinterested. A spare part was supplied but it did not work. We have now been 3 weeks without heating and only have hot water due to the fact we installed an immersion heater last year. We are reverting to a gas boiler next week after 7 winters of misery!

HMK
HMK
Reply to  Jill
6 months ago

Hi Jill, I have also had recent problems with a heat pump failure, which hopefully will be resolved next week, but I note your other problems concerning loss of heating when your heat pump goes into domestic hot water mode. This is normally due to the buffer tank installed on your heating circuit not being large enough, so there is not enough pre-heated water to maintain radiator temperature when in domestic hot water mode. Some of the heat pump units come with an integral buffer tank, this is rarely large enough for the demands of the average central heating system. My original installers guided me away from the integral buffer tank for this reason and my heat pump has happily coped with providing sufficient hot water, both domestic hot water and a central heating system with 13 standard radiators maintaining indoor temperatures up to 22C.

Derek Marsh
Derek Marsh
Reply to  Alison Gray
1 year ago

Hi Alison Gray,

I was sorry to read about your problems with your ASHP.
Mars has suggested that I try to resolve some of the readers problems. Did you get yours sorted?
If not, if you can provide details of your system Model/Type etc, along with House Type/Size, I can check the specification and see whether it is undersized for your property.

Ed
Ed
1 year ago

I have used commercial heat pumps both in Michigan and in Washington State for over 30 years. I have been pleased with the energy savings and efficiency. I got likes from you for comments I made on three of Eddy Winko’s blog dating back to 2017. so I thought I would check your blog out. Warmest regards, Ed

trackback
1 year ago

[…] to keep your sewage treatment tank healthy, to big things like installing solar PV panels and an air source heat pump to get off oil central heating and using renewables to their […]

Lucy Milton
Lucy Milton
1 year ago

Hello Mars,

I’ve spent a large part of today reading all your information about air source heat pumps which has been fascinating. Thank you so much for taking the time to put all this together.

I am considering using this technology for a holiday home which is based in the Lake District and rented out to guests throughout the year. We don’t’ live nearby so rely on local people to help run the cottage and sort out issues as they arise. The heating system currently uses LPG bottles and I am keen to get away from the problem of ordering and changing gas bottles. I want a system that requires as little intervention as possible!

Given that we do not live at the property, do you think the air source heat pumps are as reliable as any other heating system? I was concerned about your comments about defrosting the air pump in cold conditions. Is this done automatically or do you have to actually intervene? Can you think of anything else we should be aware of in this situation?

I’d really appreciate your thoughts
Lucy

Lucy Jean Milton
Lucy Jean Milton
1 year ago

Thanks Mars, got plenty to think about now.

lucy
lucy
Reply to  Mars
1 year ago

Hi Mars,
we have deferred the project until later this year, as there is a lot of work to do in addition to the ASHP, as we want to put in new underfloor insulation and heating too.

We want to use a local firm that can do both jobs so that limits our options. We are thinking of going with a Valliant AroTHERM ASHP. One of its selling points is the refrigerant R290 with a very low Global Warming Potential (GWP) rating of 3, that allows the water to be heated up to 75 degrees C without use of mains electricity. SCOP values 3.63 for 55 degreesC and 4.8 for 35 degreesC. However the Grant UK Aerona is also a contender with SCOP 3.72 for 55 degreesC and 5.4 for 35 degreesC.

If anyone has experience of these ASHP that would be interesting to hear.

Pavan Chaudhary
Pavan Chaudhary
Reply to  lucy
1 year ago

Hey Lucy. I have also opted for the Vaillant for the same reason. I am going to install it as a hybrid with a system boiler. i dont know where you are based (i am in London) but am happy to do an introduction.

Robbie
Robbie
Reply to  Mars
1 year ago

I self built my house 3 years ago with ICF (insulated concrete formwork). Its 260m2 with double height vaulted ceilings. I installed a 5kw Mitsubishi Ecodan which copes sufficiently with the extreme cold we get here in Aberdeen. I have underfloor heating throughout and a 210ltr thermal store which has a huge plated heat exchanger to provide mains pressure hot water.
We have our Hive set at 23degrees and in the recent cold snap of -8degrees it coped sufficiently.
A few people on here seem to be missing the point. It’s not the heat pump that’s the problem. It’s how well insulated and airtight your house is!
Heat loss is everything when using an ashp. Also flow rate is critical for the performance of the pump to live up to manufacturers instructions.
It always amuses me when people slate their equipment when it’s highly unlikely it was sized for purpose.
I’m a heat pump installer and there’s a phenomenal amount of information required in a heat loss calculation before a correctly sized heat pump should be installed.
An average new build has 5 air changes per hour. Mine has 1.5. This all down to how well insulated and airtight the building is.
If you get this right from the start then it doesn’t matter which heat pump you opt for, it’ll work perfectly!
BTW Vaillant aroTherm plus is what I’d recommend.

Graeme
Graeme
Reply to  Mars
1 year ago

One question , can you have a hot shower/bath with ashp? Eon are installing one at my home in next few weeks. Cheers

Steve Brockie
Steve Brockie
Reply to  Mars
9 months ago

Hi Robbie & everyone commenting.
I also live in Aberdeen, we are considering retrofitting an ASHP to the house we bought in Nov currently heated by LPG.
Robbie you mentioned it all depends on your insulation and heat moss, currently our house struggles on cold days to get to 20 degrees and when the heating goes off it plummets down through the night to about 14.
The house is 30 years old, cavity walls, 50mm underfloor insulation and will soon have 300mm loft insulation. It’s 176sqm 1.5 storey and we’ve been recommend to fit a 17hz pump. Would you say that if you have a lot of heat loss, a bigger pump will help to achieve and maintain the desired temp?

Tony Ambler
Tony Ambler
1 year ago

We took the plunge and purchased an ASHP for our house in the UK and decided on the Mitsubishi Ecodan. We also purchased 14 solar panels and storage batteries that will store 4.8 kW of power. We did this because we had to renew our 24 year old oil boiler which was well past it’s best by date. We used around £600 of electricity and 2200 liters of oil per year (approx) which cost us, last year (2019) around £1100. Total energy cost £1700. Throughout the summer our electricity cost has been reduced by about 40% and, of course, our oil bill had been removed. The colder months have seen an increase in our electricity consumption especially when we generate very little through the panels. We found that our panels through out the summer powered all of our white goods, lighting and TV’s etc and charged our batteries but heavy consumption units like our range cooker needed the grid. The winter is looking like it will use significantly more electricity but I am reasonably hopeful that it will be far less than the old combined oil and electricity cost. I will let you know.

Sam Waby
Sam Waby
Reply to  Mars
1 year ago

The noise from our LG heat pump at night (& during the day at times) means I haven’t slept properly since we bought our new eco-house. I have had the system checked and apparently there is no problem. I note that yours is situated away from the main house. Is this a problem at all as my installer insists it should not be done and decreases efficiency? Short of selling up, it may be our only option. What’s your opinion please? We have spoken before, and the situation has not improved unfortunately.

Derek Marsh
Derek Marsh
Reply to  Sam Waby
1 year ago

Hi Samantha Waby,

I was sorry to read about your problems with your ASHP.
Mars has suggested that I try to resolve some of the readers problems. Did you get yours sorted?
A noisy ASHP is normally a sign that there is something wrong. It could be as simple as too much or too little Refrigerant Gas, or something more serious.

Sam
Sam
Reply to  Derek Marsh
1 year ago

Morning Derek,
Thanks for your message, it’s very kind of you to try to help people with issues.

Our Therma V pump is brand new, and during milder spells like this works with a low hum and whoosh, which is ok. However, when it’s cold (below about 3° probably) it emits a constant buzzing noise which can be heard above our TV and is too loud to be able to sleep in our bedroom – moving us into a spare.

The builder located it rather thoughtlessly on a wall in a narrow courtyard part of our garden and it faces onto a fence and I wonder if that could be the problem?

We are considering having it moved (is this possible), buying a surround, which the manufacturer claims will reduce sound by 20 decibels, or replacing it with a Mitsubishi, as the LG engineer who came and checked told us they were quieter. This final solution may sound drastic but given that over Christmas we were considering selling this house that we only purchased in September shows just how much this noise is impacting on our lives. It feels like living with tinnitus for the cold months.

Any thoughts or recommendations would be so appreciated.

Thank you, Sam.

Derek Marsh
Derek Marsh
Reply to  Sam Waby
1 year ago

Hi Sam,

I have only just seen your message, otherwise I would have replied earlier. You don’t have to thank me, I am happy to be able to help others whilst we all suffer lockdown. Besides you have a big plus in your favour, my Daughter’s name is Samantha.
Reading your most recent comments I suspect that your ASHP is badly sited, not only from the noise aspect but also from an efficiency point of view. It may also not be functioning correctly, but we will explore that later.
Looking at the Technical Specification for LG Therma V (though it would be useful if you could tell me which model you have) it states a noise level of 52dB(A), which is slighly higher than that quoted for an Ecodan, but within the normally acceptable range.

Rather than send loads of e-mails back and forth, since it is rather difficult fault finding via e-mail (though not impossible), I would suggest that you initially watch the following video.
MESH Energy webinar technology masterclass: Air source heat pumps.
I found it whilst I was researching ASHP with a view to getting one myself. I have no involvement with the company, so there is no conflict of interest. I would just say that the video explains in sufficient detail how ASHP should be installed and commissioned for best operation,
Watch the video and then come back to me with any questions you have on the best way to get you a good night’s sleep, without you having to wait until you are old and can just remove your hearing aid.

Haresh Patel
Haresh Patel
1 year ago

I wonder if anyone has done a comparative study between air source heat pump and ground source pump. Would be very grateful if you can kindly share your experience.

I am planning to install ground source heat pump for my London (UK) home following refurbishment.

Andrew Scott
Andrew Scott
Reply to  Mars
1 year ago

We built a new house in Cornwall in 2016. We are fortunate in that a small stream runs through our property, so we opted for a GSHP and a plate heat exchanger which is quite small and much cheaper than either horizontal or vertical ground arrays. The GSHP is rated at 6.5 kW, and we have a 3.5 kW solar PV system. The house is a modest 3 bed detached and with just the two of us in residence we are not thrashing our appliances. Being a new build I have no comparative data, but our annual consumption is 3916 kWh with a max monthly in January of 590 kWh and min monthly in July of 156 kWh. Generation is 3444 kWh annually with a max monthly of 484 kWh in July and monthly min of 76 kWh in January. These figures are for 2019, but very similar from 2017 to 2020. The upshot of this is that our electricity bills are around £700 pa and FIT payments approx £550, so our annual costs are £150. On top of that we are claiming our RHI payments which are approx. £1200 pa. This is paid for 7 years so we will recover approx £7k which is the material cost of the GSHP and associated parts. This was all supplied by Kensa heat pumps. Hope this is useful information.

Jane sndrews
Jane sndrews
Reply to  Mars
7 months ago

Hi not happy with air source heating. Every winter there is a problem. It cost us about 10 pound per day in winter. We find it expensive, not like they advertise. If I had a choice I would change but that would cost a lot. Sorry no pound sign on phone. Jane ????????

p harvey
p harvey
1 year ago

They are noisy and take too much space. unless you are replacing with oil and live in the country in a detached property – you cannot beat GAS

Brian Mallalieu
Brian Mallalieu
1 year ago

Thanks for your informative & interesting video. I take it the ASHP is also providing you with DHWS for washing etc. and it would be helpful if you provided more details about your experience with it and comparisons & costs hitherto?

Danielle Strachan
Danielle Strachan
1 year ago

This has been very interesting to read thank you- we are currently looking into getting an outdoor heat pump.

We have just been told the total cost is £11k but after w government grant we only need to pay 3.5k- but I’ll still not sure if it’ll be better for us than what we have. We live in w small town in Scotland and our town doesn’t have gas at all.
We have an old economy 7 electric boiler.

I’m gonna do a bit more research before we make a decision

David
David
Reply to  Mars
1 year ago

The green energy grant and rhi payments would come from the same pot of money allocated to your project, so the total amount would be the same. If you use the grant that amount would get subtracted from the total rhi you would otherwise receive. Benefit is a big lump near the start as opposed to bring spread over 7 years. We have 1 property on an ashp installed 2 years ago and it’s amazing…. Rented out currently. Our own house is having 1 fitted in a few weeks, a gen 6 Samsung 16kw monobloc. The other house is a gen 5 in a big 3 bed semi, average Elec cost is 80 quid per month

Danielle Strachan
Danielle Strachan
Reply to  Mars
1 year ago

After all this time through Covid we finally got an ecodan heat pump installed after 3 cancellations due to Covid. It’s only day one so in early stages. But the radiators don’t seem to want to go last 16 degrees even though it’s set at 22 ????

Richard Dobbs
Richard Dobbs
1 year ago

Very interested in your helpful blog Mars. We are looking to install ASHP. We are a flat and can install on the balcony. We are around 150m2 area overall and have 2.7m high ceilings. Any thought on output needed? We are ‘all electric’ 3 phase with a wet rad system so currently two 9 kW boilers really use a lot of juice! 7 kWh LG R32 is recommended but sounded a bit underpowered to me….

Wolfgang Küchler
Wolfgang Küchler
1 year ago

No one has mentioned insulation? Can you – and other commenters – tell us anything about how well insulated your homes are, the type of windows, draught stopping? There’s a lot of concern about putting heat pumps into thermally “leaky” buildings. Also ground source is supposed to be better, also in terms of noise – any comments on that from anyone?

Andrew Scott
Andrew Scott
Reply to  Wolfgang Küchler
1 year ago

We built a new property so were able to design a well insulated thermally efficient house. We have 100mm foil backed PU insulation layer in the floor with underfloor heating in a 60mm screed on top, the internal structure is timber frame with 125mm foil backed PU insulation in the walls and roof. We have high efficiency double glazed windows and doors. We have a Kensa ground source heat pump, which is quite noisy, but no more than the oil fired boiler at our previous house and as we designed the house we created a separate small room to house the boiler UFH pumps, manifolds and all electrical and IT equipment. Being in a separate room, the noise is no more than that from our fridge/freezer in the kitchen

RALPH Brunjes
RALPH Brunjes
1 year ago

Before we had our heat pump installed we happy and the anual bill for gas was about £2000-£3000 , since getting rid of LPG and haveing all the house run on electric our electric bill is £1320 we also run two big American washer and drier. We do have solar panels and get money back each reading but obviously depending on weather it is different each time . We also live in the far North of Scotland , wet windy cold hot. Three seasons in one day.
So far we have been very happy with the heating unit apart from the control panel, it goes crazy every time we have a power cut . But we were told that it is an old model.
With us both being disabled we tend to have the heating on 24/7.
So in conclusion I personally think that it is a great unit . We have a double fan unit and it heats a large 4 bedroom 2 reception detached bungalow.

steven murphy
steven murphy
1 year ago

they are noisy – unsightly – and expensive – neighbours complained about fan noise and heat exchanger fan
GAS IS THE BEST IF YOU ARE ON THE GRID – had to have additional heating on in the water and electric boost for the hot water
could not wait to get rid of it
never again

Ian Knight
Ian Knight
1 year ago

Hello. I’m thinking of replacing our conventional gas boiler (CH & HW) with one, or two, air source heat pump(s). i.e either one to do both jobs or one to do the CH and a smaller independent (internal?) one for the HW. We have a 5-bed detached house with hot water tank and radiators. Double glazing and insulation are OK but may need improving. We’re on mains gas but obviously that’s a limited resource and prices are only going to increase, our boiler will need replacing soon so I’m thinking ahead about a renewable alternative.

A couple of initial queries you may be able to help with:
– the size (power) of unit required. Our gas boiler is rated at 18kW but some websites indicate a 4 bed house needs just an 8kW unit.
– whether the heat pump can be a straight swap for our boiler, or whether a new cylinder is also needed. Some manufacturers imply that the cylinder must be replaced, but in other places they say it can be a straight swap. Your write-up seems not to mention the cylinder.
– running noise. The main components are a big fan and a compressor. Although we are in an urban neighbourhood we want to keep the noise levels down. Your house seems fairly rural, do you have a sound recording of the unit runnung?

Thanks, Ian.

Desiree White
Desiree White
1 year ago

Have recently had a ashy installed to replace an old gas boiler. Although it heats the house up well am worried about the running costs. Listening to your video would it be better to keep the temperature constant all day. Have a Nest thermostat and use this to control the temperature. At moment I have the heating set to 15.5 at night and 18 during the day but wonder if it would be better set at constant 18.

Yvonne Warman
1 year ago

We live in a detached house of about 100sq Mtrs. Correctly our newish economy 7 storage radiators plus hot water costs about £1600 a year. Would an ashp save me money?

Rosie
Rosie
1 year ago

Hi, we currently have a gas warm air central heating system in our 5 bed house and given we are considering replacing the majority of the floor downstairs and likely with underfloor heating, we want to look at ashp. Possibly alongside pv solar panels. Current heating just has a dual which has to be turned to alter heat levels which means it’s hard to control temperature. Is ashp likely to save us money? As well as green incentive.
We are detached but very close to neighbours, is the noise likely to cause us all issues?
Thanks

Rosie
Rosie
Reply to  Mars
1 year ago

Thank you, that’s what I’ve been reading. We plan to be in the house at least 30 years, so whilst we are replacing the floor, feel like we should consider underfloor heating and therefore ashp, especially considering the future of gas. But don’t want to do this at increased ongoing financial cost.
How would we estimate the potential annual cost?

Samantha Waby
Samantha Waby
Reply to  Rosie
1 year ago

Hi Rosie,
Apologies to Home Farm who I know are great supporters of heat pumps;however, I would personally ask you to think extremely carefully before proceeding.

We purchased a £700,000 eco house in September which has underfloor heating powered by a pump. 3 months later we will we could sell up and walk away. The noise from the pump is horrendous and can be heard over the tv, and I haven’t been able to sleep without earplugs or tablets – and even then am disturbed by the noise.

The house is never warm. We have given up on heating 4 bedrooms and struggle to get others above 17 degrees.

And all this for bills of nearly £300/ month. I accept this is simply our experience, but as I dearly wish I’d never bought a property with this technology, I wish someone had shared these possible issues with me.

Good luck,
Sam

Rosie
Rosie
Reply to  Mars
1 year ago

Thanks. Other than the unit, what physical alterations are needed to heat a property by ashp?
I am assuming underfloor heating is a wet system so would be costly to dig up the floor to install?
We have a warm air heating unit but no ducting. And the ashp would probably need to be on the rear of the property and I’m worried the front of the house would be cold?
Thanks

Brian Mallalieu
Brian Mallalieu
Reply to  Rosie
1 year ago

Rosie, do you have good all round insulation to the rooms being considered for u/floor heating? If so, have you considered DIY elecric heating e.g. Warmup?

Sue Fawn
Sue Fawn
1 year ago

New user of ASHP

Susan Fawn
Susan Fawn
Reply to  Mars
1 year ago

It was installed by our developer in 4 new homes on Welsh border. A Grant system.

Susan Fawn
Susan Fawn
Reply to  Mars
1 year ago

Hi Mars
Only about 5 weeks since we moved in. We have sophisticated digital room sensors in each ground floor room underfloor heating and rads on first floor. There are week and weekend settings and one on first floor setting the temp for all bedrooms. Most are set at 20.5 with bedrooms at 19, nd the house remains warm 24/7.
We have used 1100 kws in about 30 days incl appliances etc.
I will be applying for the Renewable energy incentive scheme.

Will be interesting to see the net cost over 12 months. We have moved from the sunny south coast with south facing gardens to a wetter climate and rural setting but well worth it for the peace/hills around us and views to die for!

Sue

Dv
Dv
1 year ago

Been looking at ASHP for our cottage and very pleased I found this site, while not decided on a brand I’ve found installers have their favourites, I would be keen to hear of noise levels for Nibe and Valiant if anyone’s got experience of them

TD
TD
1 year ago

Thanks for putting the video together Mars. Very informative and interesting.

We also live in a converted farmhouse (Yorkshire) and have no mains gas, so our primary heat source for central heating and hot water is oil. The boiler is now close to 30 years old and I am sure it won’t be long before it fails beyond economic repair. We only rum the boiler through the winter and only in the evenings. It’s a five bedroomed property with around 240sq M floorspace. We only have radiators, so no underfloor heating. Through the summer and in the winter we also run an immersion heater on Economy 7 to provide, or boost the hot water.

I am in discussion with an ASHP installer about converting our system, including upgrading the radiators and installing a new heat store tank.

Would you mind telling me roughly what your floorspace is and what was the output of your old oil boiler that the 16kW ASHP replaced. How many rooms are there in your farmhouse?

We like the idea of 24/7 background heat and if we went with a well set up ASHP we would be able to eliminate the estimated £500 per annum immersion heater cost , as well as the 2400 litres of oil we use.

Do you know how many kW your ASHP has used over the period of a full year.

It would be great if I could get an idea of how your property compares to ours and how much electricity you have used to drive the ASHP. Whilst I understand the theory and the sales pitch being given to me by the installer, it would make sense to sense check their projections against a similar property. They are proposing a 17kW unit.

Thanks in advance for any insight.

TD
TD
Reply to  Mars
1 year ago

Thanks for the quick reply Mars.
Unfortunately the installers have come back to me this afternoon and told me that it doesn’t look cost effective. Mainly due to the location, layout and age of the property.
Their calculations indicate that we would need 2 x 12kW ASHP units to guarantee sufficient output. And we would need a 3 phase electricity supply to handle the start up surge current requirements of both units (even though the units are DC inverter based). They were proposing units manufactured by Grant.
They did suggest that a hybrid type system could be an option, utilising a smaller oil boiler to supplement the ASHP, but they recognised that again this wasn’t a cost effective solution, due to the initial capital cost.

I may get a second opinion. But as they were so thorough in their evaluation and honest enough to advise against it, I am not sure that a second opinion will tell me a great deal more.

I’m going to update the boiler controls so we can trial running the boiler for longer periods, but with a lower room temperature setting overnight. Doing this should eliminate the need for the immersion heater. Also, I will balance all the radiator flows and adjust the circulation pump speed so I can optimise the delta between the flow and return temperatures.

Then I’ll start investigating more efficient oil boilers, as sooner or later our old one is going to pack up completely and be too expensive to repair.

Never a dull moment!!
Thanks again for your reply

TD
TD
Reply to  Mars
1 year ago

Second installer has looked at the house and they have also concluded that we would need 26KW ASHP and most of the radiators changing for it to work satisfactorily.

So now working on plan B which is a more efficient condensing oil boiler which we will locate externally to reduce noise and free up space in the kitchen. Awaiting two quotations. Part of the work will involve converting the hot water and central heating circuits to valved control which I am told helps efficiency as well. I have also installed a Hive control system myself which is giving us better control over the times and temperatures for the central heating.

Since we are now running the boiler more often I have been able to switch off the electrical immersion heater which ran on Economy 7 overnight with a 2 hour boost around tea time.
We don’t have a smart meter, but I have been monitoring the E7 consumption for close to a month now and it has dropped by an average 4.5KwH per night over the past 30 days. I’m not sure exactly how much we have saved by not running the immersion heater through the day, but we have also not needed to put on any electric heaters during the day. Looking at the average daily consumption from historic bills for winter last year, compared to the last 30 days, I think we are saving around 4.6KwH on the day rate as well. On our current tariff from E.ON the combined day and night savings equate to circa £335 a year.

It’s early days and I don’t yet know how much extra oil we are putting through the old boiler, but the £335 electricity saving will buy us close to 850 litres of oil to offset against the extra boiler use.

Hoping that a new condensing boiler with a claimed efficiency of +/- 94% and a more efficient valved flow control system will help to reduce our oil consumption significantly compared to the old boiler which has a published efficiency of 70%. (and that assumes it is running as well as possible!!)

At 94% efficiency I think it should also be more economical to heat the hot water only through the summer than using Economy 7. If I’ve got my maths correct. then our current Eco7 cost per unit is £0.066 (and likely to increase when the current contract expires in April). 1 litre of kerosene is £0.35 which works out at around £0.037 per unit at a 94% efficiency.

I guess time will tell !!

Nigel
Nigel
Reply to  TD
1 year ago

TD, I’m looking for a reputable ASHP Installer in Yorkshire, would you mind saying which companies advised you on your system?

Susan Fawn
Susan Fawn
Reply to  Mars
1 year ago

I have been reading your comments about lowest tariffs for electricity. We can’t seem to find anything much under 17p per kw. and 20p per day standing charge.Even getting a supplier to respond in offering a contract is proving difficult in this climate. We have been in our new build home since 30 Nov and still waiting for a welcome pack.

Iain
Iain
Reply to  Susan Fawn
1 year ago

My wife recommends Flipper whom she has used for years for a house she managed. For a small annual fee they will monitor electricity prices and will suggest that you switch to keep in the best available deal. They ask you if you would like to switch then do it for you if you say yes. She swears by them.

Julian C
Julian C
1 year ago

Very useful site – thank you. We live in a 2700sqft 20 year old bungalow. We have triple glazed, doubled the loft insulation to 300mm, blocked up drafts, a new A Rated oil boiler 6 years ago, 4kW of Solar PV and an electric diverter that uses spare electric to heat hot water. An electric car too 🙂 We currently use about 1200-1500L of oil per year and about £45 of electric / month. Our home has an EPC rating of B and energy demand of 20,000kWh.
I continue to be keen to drive down our CO2 output, so was investigating an ASHP solution. Mrs C has said “NO” to underfloor heating or radiator enlargement (note: we already have quite a lot and large radiators).
I have been investigating an Hybrid ASHP system – an 8kW Samsung unit would be added to our existing oil boiler to cover “80%” of our heating needs, the remaining 20% the oil boiler would kick in. It would be funded through RHI – they system would be cost neutral, only having to pay for electricity.
So my questions would be: your thoughts on an Hybrid System? I note you kept your old boiler – how often does it kick in? Where did you find an energy supplier at 10p/kWh? I pay 14.5p and 5p for 4hrs at night to charge the EV. Any advice or wisdom gratefully received

Julian C
Julian C
Reply to  Mars
1 year ago

Evening Mars. Thanks for the continued ASHP discussion on this site. I think I’m moving away from the idea of an hybrid system, keeping our oil boiler & adding an 8kW ASHP. Instead I’m pursuing the idea of a Daikin Altherma 3H HT 16kW system. HT = high temperature. It’s also super quiet. Calcs show an electric demand of 7300kWh to deliver the 20000kW of heat. Daikin has a 10 year fixed price service package which I like. But their monitoring and links to agile tariffs is missing. I’m also looking at the mixergy hot water tank.

LJA
LJA
1 year ago

Hi Mars,
Thank you for sharing your data and experiences, all very interesting. Currently planning a new build in the North of Scotland and hoping to install a 7kW Panasonic ASHP. House is a single storey, 110m2 with wet under floor heating throughout. The ASHP must also provide hot water (2 sinks and a shower) for 2 adults, and a heated towel rail in the bathroom. We have had guidance on selecting the heat pump and tanks, and we are happy with the size. The house will be very well insulated with triple glazing, although not quite passivhaus standard. We were advised around 3kW to heat the home. We therefore hope that the ASHP will rarely need to be running at 7kW, and mostly be using much less power.
I just wanted to ask, from your experience, how does the ASHP usage vary over the day – how often does your system draw the full 18.8kW?

Andrew Scott
Andrew Scott
Reply to  Mars
1 year ago

Regarding the ratings of heat pumps, what is classed as an 18 kW heat pump has a maximum ‘theoretical’ output of 18 kW of heat. Obviously in optimum conditions, and due to the COP, the input energy will be much lower. We have a groundsource heat pump rated at 6.5kW, and the compressor motor which is the majority of the load is a 2.2kW, drawing approximately 1.5 kW in operation.

LJA
LJA
1 year ago

Thank you both 🙂
That’s really helped to clear that up for me!

Julian C
Julian C
1 year ago

Links to note on 8th Jan. Thank you. I have since been talking to a different ASHP supplier / installer. Having done the demand and loss calcs he is proposing removing the oil boiler completely and installing a 16kW Daikin HT system and a new h/w tank. Higher price (but only by £3k) but I like the idea of no oil. Also no radiator changes which my wife very much prefers. Keep up the information and good work. I am only upset by how tidy your place is compared to mine 🙂

Paul Coathup
1 year ago

Hi,
I am in the process of designing a new house approximately 300m2.
My preference is to install a ground source heat pump with a surface array but unfortunately I don’t have sufficient adjacent land available and vertical bore holes are looking prohibitively expensive.
Does anyone know if it is possible to combine an air source heat system with a ground source system to provide the warm supply water to the compression heating system. ?
I hope this question makes sense to someone.
Thanks Paul C.

Andrew+Scott
Andrew+Scott
Reply to  Paul Coathup
1 year ago

Hi Paul,
We have a GSHP, and despite not having sufficient land for a ground array were fortunate to have a small stream which we abstract from to provide our heat source. I am struggling to understand why you would consider combining an ASHP and GSHP. Both can provide the source of heat for underfloor / wet systems, unless you mean to have both systems with the ASHP assisting the GSHP due to limited ground array?

Paul Coathup
Reply to  Andrew+Scott
1 year ago

Hi Andrew,
Yes, you have the gist of my question.
Is it feasible and realistic to combine an undersized ground array with an air source system ?

Andrew+Scott
Andrew+Scott
Reply to  Mars
1 year ago

Having worked in process engineering for many years, there is, in theory no reason why you cannot use both a GSHP and ASHP on the same heating system. The issue will be finding a supplier to design and commission a suitable control system. In essence, you have a warm water heating circuit on which your building is imposing a heat load or demand. This requires a heat input to maintain a temperature set-point. A control system with temperature transmitters on both the heat source inlet and outlet connections will determine if the boiler is increasing the circuit temperature at a pre-determined rate. If the programmed conditions are not satisfied, i.e. inadequate heat input, then it will demand a second heat source to assist. This will be the case for commercial properties with boilers, but my experience in this sector is very limited. To a control system designer would be a simple process but really you need to find a standard heating control system on the market, as bespoke control systems will most likely be prohibitively expensive. I will do a bit of research, and post a comment.

Andrew+Scott
Andrew+Scott
Reply to  Mars
1 year ago

This article is worth a read on cascade boiler control systems. More for commercial systems, but the principle is commonly used.
https://modbs.co.uk/news/archivestory.php/aid/12710/Cascading_control__.html

Andrew+Scott
Andrew+Scott
1 year ago

Here we are. This is an off-the-shelf solution, but the system design will need careful consideration. It will need a heating engineer rather than a plumber!
https://www.vaillant.co.uk/commercial/products/vrc-630-boiler-management-control-37568.html

Andrew+Scott
Andrew+Scott
1 year ago