Talk Morgan Forums Community Vehicle Talk (non-Morgan) Air Source Heat Pumps

It looks as though we might be building another house..........🤷🏻‍♂️
We are being pushed towards an air source heat pump over a gas boiler.
I know the green argument is that we must for the sake of the planet, but I don't really think that my little house will have a great deal of impact on the fate of the planet.
I'm much more concerned about cost and the heat they produce.
Gas is cheaper than electric, boilers are cheaper than ASHP's. PV's and batteries are expensive.
It looks as though under floor heating is the way forward, but I'm not really a big fan of that either, but it'll probably have to be the solution for down stairs.

So.... Has anyone got an ASHP and if you have, what do you think..........?
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Like anything you ask on t'internet you'll get a lot of polarised anecdotal answers (often reflecting the poster's opinions and prejudices) ... don't have one myself as I prefer dead basic tech of wood fired Rayburn and stove (though we did see this coming down the road 30+ years ago and moved well out to somewhere with our own woods so not really typical) ... with a new build you'll be subject legislative restrictions I presume. All I can add is that a couple over the back of us built new and were required to fit one .. year down the line took it out (no doubt at some expense) and put in a boiler ... yet another anecdote, but real and reflecting an experience of living with one.

K

I have not fitted a heat pump yet. I have, however researched them. Here are some of the things I have found out:
1) They work well in a new-build - you will be able to design the house, its insulation and radiators / underfloor heating to suit the lower flow temperature of a heat pump.
2) Before selecting a system, do some due diligence on repairability and parts supply. They have one at the stables where we keep our horses in one of their rental houses that has been offline for nearly a year waiting parts making the house unlettable. They are seriously considering ripping it out and fitting a new replacement - at substantial expense - because they cannot get parts for the broken one.
3) There are high flow temperature heat pumps available now - but I haven't found one that quotes efficiency at the higher flow temperature.
4) You will have to get used to a different way of working compared to gas boilers. Most people run the gas boiler when they want heat and have it turned off for big chunks of the day/ night when not needed. Heat Pumps are more effective when run almost continuously.
5) People I have spoken to who have fitted them as part of a planned upgrade including insulation and other elements won't go back to gas.
6) My brother has researched heat pumps as a replacement for an elderly oil fired boiler and concluded that the cost of upgrading insulation and pipework in his 60 year old house combined with the cost of a heat pump makes it untenable for him.
7) When I did my research, ASHPs were 300% to 500% efficient compared to 90% for a typical gas boiler. At our current rates (Octopus), we pay 22.6p/kWh for Electricity and 5.62p/kWh for gas. That means that an ASHP needs to be at least 360% efficient to break even on our tariffs.
8) Average flow temperature ups 37.5oC compared with 70oC for a gas boiler.

Well we have one and pleased with it so clearly biased It came fitted to the new build three bedroom bungalow we moved into 3 years ago and is coupled to underfloor heating with individual thermostats in each room plus a tall 167 litre hot water tank. Quiet in operation with worst case current draw around 2.5kW mid winter. Pump output temperature is lower than a gas boiler but offset by increased flow controlled by intelligent circulating pump. This also means that immersion heater is needed as top up during the winter but for barely an hour each day and mainly to ward off Legionnaires disease. We have 3kW of solar as well with FIT and have electricity (only energy source) bills between £15 and £30 during summer months.

You need the most insulated house you can get due to the low temp differential of the ASHP hot water vs the room temp.

I have a friend in Sweden with one on his small summer house that works well, but is insulated to Nordic standards.
The outside units can be loud , they are effectively the same as those split AC units you see on building with a fan etc.

Ground source heat pump will work better if you have the land to bury the pipes. I guess on new build you have that chance.

I know Octopus do a special tarriff. Called Cosy Octopus
Day rate:

25.25p / kWh
Cosy rate (04:00 - 07:00 & 13:00 - 16:00):

12.37p / kWh
Peak rate (16:00 - 19:00):

36.62p / kWh
Standing charge:

47.85p / day

I would get the help of a specialist installer to tell you what makes sense. I'm keeping gas for as long as possible. Lets us know the conclusions.

My PV & battery set up is running at a 7 year pay back & that should reduce to 6 or less when I move to a smart tarriff. Cost was under 8k for a 3.6kWh array & 4.2kWh batteries. We have generated 80kW in April & imported 10.6 kW & we exported 8.9 kW.

Check out www.heatgeek.com for informed information these guys have been trying to get the UK installers up to spec on heatpump installations, rather than just a jobbing plumber having a stab at it and likely making a balls up of it.

Whatever heat source you choose Julian aim for greatest insulation on your new build. I think the current minima is for 5½" cavity, we have 8".

I suspect that the old style heating systems compared to the new may come close to matching the comparison of old style ICE Vs EV in terms of cost to benefit analysis..? Also the increase of complexity in the modern systems compared to the old, as Paul points out in his post, there can be reliability issues with cost implications relative to that additional complexity.

additional complexity..? From what little I know of modern systems your average plumber`s knowledge of such systems may also be similar to the average mechanic skilled enough to work on a Trad, then being faced with resolving digital related issues on an EV...? It seems that the KISS principal has been lost to the sands of time..?

I suspect insulation is the primary factor in any build relative to the long term heating costs, pity the govt ditched the grants, leaving it to those who could afford to modernise, be that home heating or motor transport related....Hmm..?.

All just part of the evolutionary processes and govt priorities..?

Basic thermodynamics says that the efficiency of a heat pump falls as the temperature difference between input and output increases. So its less efficient in winter than in summer. As Paul F points out, a min efficiency ( in his case 3.6) is necessary to make a heat pump cheaper than simply having electric radiators.

I doubt the complexity argument. Basically a heat pump is simply a fridge turned inside out ( ie the hot bit at the back of the fridge is inside your house and the cold bit of the fridge is outside trying to cool the atmosphere) which is well established technology. I dont see why it would have any fancier control systems than a modern condensing boiler.

As the erudite Luddite suggests, insulation is the real key. A human being generates roughly 2kwh per 24 hours which is why some modern offices dont have heating systems but rely on the occupants. So start off by insulating to such a level that you keep that heat inside. Plus the heat of cooking etc. Even the dog!. No draughts. Small windows.

I would give serious consideration to pure electric heating - the likely extra running cost could well be less than the repair/ mainetnance / installation cost of a warm water system whether gas or heat pump. They dont need moving parts

Dont get advice from a plumber. Chose an engineer ( proper degree type not an uprated plumber) to understand the nackground

Howard it is also why ground source heat pumps are better that ASHP as the ground temp is constant.