Air Source Heat Pumps / systems - any real world experience?
Discussion
Hello all,
We are considering an Air Source heat pump and heating system upgrade to our house. The reasons behind this are
1 - Current boiler is original fit for the house (20 years old). Although not showing any issues is getting on a bit
2 - we are doing some extension works to our house and part of this is to add underfloor heating to the kitchen. current system is not capable of this.
3 - there is a nice £5k grant off the whole job.
Our house is fairly modern (built around 2000) and is pretty well insulated, but realistically are air source heat pumps actually any good.
I have been running the numbers and it doesn't seem that it will be much cheaper (if at all), but the theory is that gas will get more expensive so energy bills should go up less than if we stay with Gas
Question is, do they actually heat a house sufficiently well to justify the change, or should i just look at a new boiler when the current one gets iffy and just put an electric element under floor heating system into the kitchen?
We are considering an Air Source heat pump and heating system upgrade to our house. The reasons behind this are
1 - Current boiler is original fit for the house (20 years old). Although not showing any issues is getting on a bit
2 - we are doing some extension works to our house and part of this is to add underfloor heating to the kitchen. current system is not capable of this.
3 - there is a nice £5k grant off the whole job.
Our house is fairly modern (built around 2000) and is pretty well insulated, but realistically are air source heat pumps actually any good.
I have been running the numbers and it doesn't seem that it will be much cheaper (if at all), but the theory is that gas will get more expensive so energy bills should go up less than if we stay with Gas
Question is, do they actually heat a house sufficiently well to justify the change, or should i just look at a new boiler when the current one gets iffy and just put an electric element under floor heating system into the kitchen?
XJSJohn said:
Hello all,
We are considering an Air Source heat pump and heating system upgrade to our house. The reasons behind this are
1 - Current boiler is original fit for the house (20 years old). Although not showing any issues is getting on a bit
2 - we are doing some extension works to our house and part of this is to add underfloor heating to the kitchen. current system is not capable of this.
3 - there is a nice £5k grant off the whole job.
Our house is fairly modern (built around 2000) and is pretty well insulated, but realistically are air source heat pumps actually any good.
I have been running the numbers and it doesn't seem that it will be much cheaper (if at all), but the theory is that gas will get more expensive so energy bills should go up less than if we stay with Gas
Question is, do they actually heat a house sufficiently well to justify the change, or should i just look at a new boiler when the current one gets iffy and just put an electric element under floor heating system into the kitchen?
Unless you're going to fit wet underfloor heating throughout your property (£££), you'll need new radiators which are twice the size of your current ones.We are considering an Air Source heat pump and heating system upgrade to our house. The reasons behind this are
1 - Current boiler is original fit for the house (20 years old). Although not showing any issues is getting on a bit
2 - we are doing some extension works to our house and part of this is to add underfloor heating to the kitchen. current system is not capable of this.
3 - there is a nice £5k grant off the whole job.
Our house is fairly modern (built around 2000) and is pretty well insulated, but realistically are air source heat pumps actually any good.
I have been running the numbers and it doesn't seem that it will be much cheaper (if at all), but the theory is that gas will get more expensive so energy bills should go up less than if we stay with Gas
Question is, do they actually heat a house sufficiently well to justify the change, or should i just look at a new boiler when the current one gets iffy and just put an electric element under floor heating system into the kitchen?
If your current boiler is a combination boiler, you'll need a hot water cylinder installed.
Heat pumps are much slower to heat these new giant radiators than your boiler was at heating your smaller radiators, so factor in that you'll need to keep it on more to maintain a constant temperature.
They still use electricity, a fair chunk of it. It will cost more to run than a boiler by a good margin unless you thermally wrap your house. Electricity will only increase in price as will gas, but gas is 6? times cheaper than electricity for heating.
Unless you're a dreadlocked warrior who wanted to live on a narrowboat but you're settling on a heat pump, or you're doing a new build, I'd stick with the boiler.
I quite often see discussions about heat pumps only being viable if you spend a lot of time/effort insulating your house first but it doesn’t seem to be comparing like for like.
Presumably, on a cost basis it would be:
Draughty house + gas boiler > Insulated house + heat pump > Insulated house + gas…
Basically, once the house is properly insulated, isn’t gas still cheaper than a heat pump?
Similarly, what would the comparison be if you fitted big radiators/underfloor heating but then just run a gas system at a lower temperature?
Presumably, on a cost basis it would be:
Draughty house + gas boiler > Insulated house + heat pump > Insulated house + gas…
Basically, once the house is properly insulated, isn’t gas still cheaper than a heat pump?
Similarly, what would the comparison be if you fitted big radiators/underfloor heating but then just run a gas system at a lower temperature?
both your comments above are where i am starting to come around to thinking too ....
It seems to be the new version of an economy 7 storage heater, and they were crap.
to make it work, the house has to be built to such a thermal efficiency, and although my house is pretty new, i am 100% sure that its not at that efficiency.
yet, if i were to get it to that level of efficiency, then again, as mentioned, surely the gas heating would also still be that much cheaper.
the only place that it unravels is if a KWh of gas eventually costs more than a KWh of electricity, and i assume we are a long way from that, and when we are at that point, there will be significantly better solutions on the market,
I think that the air source plan is in the bin for now, i will stick a few grand aside as a sinking fund should the boiler s
t itself.
It seems to be the new version of an economy 7 storage heater, and they were crap.
to make it work, the house has to be built to such a thermal efficiency, and although my house is pretty new, i am 100% sure that its not at that efficiency.
yet, if i were to get it to that level of efficiency, then again, as mentioned, surely the gas heating would also still be that much cheaper.
the only place that it unravels is if a KWh of gas eventually costs more than a KWh of electricity, and i assume we are a long way from that, and when we are at that point, there will be significantly better solutions on the market,
I think that the air source plan is in the bin for now, i will stick a few grand aside as a sinking fund should the boiler s
t itself. Here's something I've been pondering and would appreciate people's thoughts.
At request of She Who Must Be Obeyed I've been investigating some air conditioning kit, not that intensely must admit.
Anyway have discounted the ones which require pipes to be hung out if windows or some other venting arrangements and quickly started looking at split wall systems.
Also quickly looked at those which aren't the things you sometimes get in cheap hotels but the devices where there are wall mounted output units and an outside unit, which of course are in reality air to air heat pumps.
To change our current boiler and central heating system would be a major job, although house is well insulated, probably could do a bit more in the roof space, radiators need changing and all the microbore pipework would need upgrading. Major upheaval and redecorating job all round probably. Not cheap.
Now we have a reasonably up to date Vaillant boiler, and such is the setup that even in the coldest weather the boiler rapidly modulates to its minimum output of 5kw. Even when it's significant minus degrees outside, at least significant for UK, it just sits there on min output having got the place up to temp fairly quickly.
Hence my thought is the possibility to install a multi split air to air heat pump, say a couple of 9,000 or 12,000 btu wall mounted output units strategically placed, can heat or cool.
Thoughts? Pitfalls? Clearly has to be installed by approved fitters and fitting cost would depend on getting from the heat pump to strategic locations for wall units. But that's another question not for Internet really.
I have experience of an ASHP single outlet in Sweden heating a large hall and open stairway to upstairs, and the Mitsubishi unit kicked out some fair heat even in a Swedish winter.
At request of She Who Must Be Obeyed I've been investigating some air conditioning kit, not that intensely must admit.
Anyway have discounted the ones which require pipes to be hung out if windows or some other venting arrangements and quickly started looking at split wall systems.
Also quickly looked at those which aren't the things you sometimes get in cheap hotels but the devices where there are wall mounted output units and an outside unit, which of course are in reality air to air heat pumps.
To change our current boiler and central heating system would be a major job, although house is well insulated, probably could do a bit more in the roof space, radiators need changing and all the microbore pipework would need upgrading. Major upheaval and redecorating job all round probably. Not cheap.
Now we have a reasonably up to date Vaillant boiler, and such is the setup that even in the coldest weather the boiler rapidly modulates to its minimum output of 5kw. Even when it's significant minus degrees outside, at least significant for UK, it just sits there on min output having got the place up to temp fairly quickly.
Hence my thought is the possibility to install a multi split air to air heat pump, say a couple of 9,000 or 12,000 btu wall mounted output units strategically placed, can heat or cool.
Thoughts? Pitfalls? Clearly has to be installed by approved fitters and fitting cost would depend on getting from the heat pump to strategic locations for wall units. But that's another question not for Internet really.
I have experience of an ASHP single outlet in Sweden heating a large hall and open stairway to upstairs, and the Mitsubishi unit kicked out some fair heat even in a Swedish winter.
@FiF, go over to this thread for Air Con advice https://www.pistonheads.com/gassing/topic.asp?h=0&...
miniman said:
At our village hall, once the outside temperature gets below 3 or 4 degrees the ASHP stops generating heat. I consider this to be a flaw.
I read something on this, but there seemed to be a lot of deflection (which is one of the areas that made me suspicious of the whole system), because we have a broad temp range and a relatively low average it's quite hard to get the right gas to generate enough of a thermal difference across the temp range that we would need heating on. HappyMidget said:
@FiF, go over to this thread for Air Con advice https://www.pistonheads.com/gassing/topic.asp?h=0&...
Thanks for pointing me in that direction, not seen that thread. Will do, though the topic is in a way across both subjects, heating and cooling, but will cross post. Probably get banned for cross posting now.
Edited to say, ended up deleting my post over there as the thread is most informative, best seen in a long while.
Edited by FiF on Wednesday 27th July 20:08
Quite freakily, OP, I’m in a very similar situation to you. Moving into a 20ish year old house with original boiler. We do have partial underfloor heating already which went into a kitchen and its extension.
Are you in Scotland? I am and we can’t get a grant til 12 months into home ownership.
I’m thinking we’ll replace boiler and insulate if required but I’m open to an alternative heat source, eg air pump.
Are you in Scotland? I am and we can’t get a grant til 12 months into home ownership.
I’m thinking we’ll replace boiler and insulate if required but I’m open to an alternative heat source, eg air pump.
Scotland: we bought a 1999 built bungalow with 20 year old storage heaters which are expensive to run even on Economy whatever, totally uncontrollable, take a day to warm up or cool down by which time the weather has changed.
We went for ASHP with new water rads throughout and new tank etc. Cost to install was circa £15K, we got a grant for £10K which we have to pay back over 7 years but we get a payment every three months that covers the repayments o the entire set up amounts to £5k. It was going to cost £10K for new style storage heaters. Rural so no gas available except "calor" or similar. Oil required a full boiler, oil tank and wet rads with no grants etc.
Electricity costs have gone up rather a lot of late (but so has Gas and Oil which aren't available). More than happy with the ASHP.
We went for ASHP with new water rads throughout and new tank etc. Cost to install was circa £15K, we got a grant for £10K which we have to pay back over 7 years but we get a payment every three months that covers the repayments o the entire set up amounts to £5k. It was going to cost £10K for new style storage heaters. Rural so no gas available except "calor" or similar. Oil required a full boiler, oil tank and wet rads with no grants etc.
Electricity costs have gone up rather a lot of late (but so has Gas and Oil which aren't available). More than happy with the ASHP.
If your EPC is C or better, and you want your house warmer then not over the course of the day (ie you don't only heat the house for the evening only) then an ASHP would work fine, if less then a C and you only need heat for a few hours when home from work, stick to gas. Having solar/PV enhances this
Over the next 10 years the government will load gas up, and encourage electricity utilisation, so worth considering it long term as well.
Its not rocket science.
Over the next 10 years the government will load gas up, and encourage electricity utilisation, so worth considering it long term as well.
Its not rocket science.
1400 sq ft house. Two of these, one in the bedroom and one in the living room keeps the house cool or warm all year round and are almost silent. 
https://www.pioneerminisplit.com/collections/wys/p...
https://www.pioneerminisplit.com/collections/wys/p...
NMNeil said:
1400 sq ft house. Two of these, one in the bedroom and one in the living room keeps the house cool or warm all year round and are almost silent.
https://www.pioneerminisplit.com/collections/wys/p...
This was something I was pondering too. What do they cost to run?https://www.pioneerminisplit.com/collections/wys/p...
Much of the heat pump negativity seems to be based on a high proportion of bad installations caused by a lack of technical knowledge in the heating industry rather than heat pumps being inherently bad per-se. Gas boilers are more often than not massively over specced for the amount of heat the house actually needs. Most normal 3-4 bed houses, even averagely insulated ones nowhere close to current building regs only need single digit Kw heat input yet most of us have gas boilers that can pump out 3x that, so a badly designed / controlled system gets hidden by simply running the boiler a bit longer or a bit hotter. Heat pumps on the other hand seem to be a finer balance, you can't run them 10% hotter and be only 10% less efficient, they need to be sized correctly and run at cooler flow temperatures to get good efficiency but if the heat pump is just installed as a direct replacement for an oversized gas boiler connected to the same 30 year old design of heating system then its never going to work well.
There's some good videos on how heat pumps can work well without insulating to within an inch of your life on the Heat Geek channel, they're obviously pro heat pump/renewables but it comes from knowledge of low temperature heating design designing systems that allow heat pumps to run efficiently and heat the house correctly rather than blind faith or sales pitches that many installers rely on https://www.youtube.com/c/HeatGeek/videos
There's some good videos on how heat pumps can work well without insulating to within an inch of your life on the Heat Geek channel, they're obviously pro heat pump/renewables but it comes from knowledge of low temperature heating design designing systems that allow heat pumps to run efficiently and heat the house correctly rather than blind faith or sales pitches that many installers rely on https://www.youtube.com/c/HeatGeek/videos
XJSJohn said:
This was something I was pondering too. What do they cost to run?
Can't help you I'm afraid, as my house is on solar. But the estimated annual running cost from the blurb is:
Cooling: $79.00 (65 quid)
Heating: $242.00 (200 quid)
Of course that depends on the cost of your power and the climate you live in, so it's more of a best guess really.
Other PH members have them so they may be able to give you more realistic numbers.
We have an ASHP and I have very mixed feelings about it.
The idea is great and has low/zero emission, something that is to be applauded. But the acid test is does it work?
I think that the answer to that question is unfortunately “it depends”.
We live in the Scottish Highlands in a traditional stone built farmhouse from around 1900. It has suspended floors, no wall insulation and very little loft insulation because of the shape of the roof (coombs). All of this means that the house is poorly insulated and all of this conspires to mean that the ASHP can not keep the house warm in very low winter temperatures, particularly below about -4c.
Also it can not run the heating and reheat a tank of hot water at the same time, so if you run a bath it can cause the heating to go off while it reheats the water. You can use different settings to solve this.
It is slow to react, unlike gas and oil, and gives a gentle heat unlike the fierce heat from those others. The radiators only get warm and not hot. I think the flow temperature is about 50c compared to around 70c for oil and gas.
The sales blurb will tell you that you will get a 3 to 1 power out to power in ratio or better, ours is delivering just over 2 to 1, and with recent electricity price rises this can make it expensive to run.
There is a reason that so many Scottish houses with ASHP still have open fires or log burners for supplemental heating in the house.
So I think that the installation of ours (by the previous owner) was a poor choice.
However we are renovating the house, so have just had all of the windows replaced and are about to have the walls and roof insulated. Then we will deal with the floor too.
Once done, the heating engineers will come back and recalculate the radiator needs and we will them give it another winter with a fair crack of the whip.
TLDR: in a well insulated house I think it could work, in an old non insulated house in the Highlands it doesn’t work.
The idea is great and has low/zero emission, something that is to be applauded. But the acid test is does it work?
I think that the answer to that question is unfortunately “it depends”.
We live in the Scottish Highlands in a traditional stone built farmhouse from around 1900. It has suspended floors, no wall insulation and very little loft insulation because of the shape of the roof (coombs). All of this means that the house is poorly insulated and all of this conspires to mean that the ASHP can not keep the house warm in very low winter temperatures, particularly below about -4c.
Also it can not run the heating and reheat a tank of hot water at the same time, so if you run a bath it can cause the heating to go off while it reheats the water. You can use different settings to solve this.
It is slow to react, unlike gas and oil, and gives a gentle heat unlike the fierce heat from those others. The radiators only get warm and not hot. I think the flow temperature is about 50c compared to around 70c for oil and gas.
The sales blurb will tell you that you will get a 3 to 1 power out to power in ratio or better, ours is delivering just over 2 to 1, and with recent electricity price rises this can make it expensive to run.
There is a reason that so many Scottish houses with ASHP still have open fires or log burners for supplemental heating in the house.
So I think that the installation of ours (by the previous owner) was a poor choice.
However we are renovating the house, so have just had all of the windows replaced and are about to have the walls and roof insulated. Then we will deal with the floor too.
Once done, the heating engineers will come back and recalculate the radiator needs and we will them give it another winter with a fair crack of the whip.
TLDR: in a well insulated house I think it could work, in an old non insulated house in the Highlands it doesn’t work.
NMNeil said:
XJSJohn said:
This was something I was pondering too. What do they cost to run?
Can't help you I'm afraid, as my house is on solar. But the estimated annual running cost from the blurb is:
Cooling: $79.00 (65 quid)
Heating: $242.00 (200 quid)
Of course that depends on the cost of your power and the climate you live in, so it's more of a best guess really.
Other PH members have them so they may be able to give you more realistic numbers.
As a really simple rule of thumb - you can get your typical heating kWh from your Epc (or your gas bill)
Divide it by 2.5 (as an average CoP) and then multiply it by your electricity rate - there is the cost of running an ASHP
The technology works pretty well and can operate with normal rads (especially if you get a high temp heat pump)
Divide it by 2.5 (as an average CoP) and then multiply it by your electricity rate - there is the cost of running an ASHP
The technology works pretty well and can operate with normal rads (especially if you get a high temp heat pump)
We’ve gone from a 4 bed 5 year old new build on gas to a brand new build in a village with no gas so it’s ASHP.
So with that in mind our house is Uber insulated. Wet underfloor downstairs etc.
It does work. But I wouldn’t say it’s brilliant. We have a log burner to help on real cold nights/days.
The problem is it’s not quick to react. And the temperature of the rads only gets to 40 max. So it absolutely works in our house. But you can’t open doors and windows to long on dark cold days. As if you lose that air temperature to quickly it takes an age to get back.
I would not entertain the idea if you don’t have wet underfloor, loads and loads of insulation and new windows doors.
We have used about 5,500 kWh units in a year just on the ASHP. So at 30p a unit. It’s not cheap. Also used 3 tonne of logs!!
So with that in mind our house is Uber insulated. Wet underfloor downstairs etc.
It does work. But I wouldn’t say it’s brilliant. We have a log burner to help on real cold nights/days.
The problem is it’s not quick to react. And the temperature of the rads only gets to 40 max. So it absolutely works in our house. But you can’t open doors and windows to long on dark cold days. As if you lose that air temperature to quickly it takes an age to get back.
I would not entertain the idea if you don’t have wet underfloor, loads and loads of insulation and new windows doors.
We have used about 5,500 kWh units in a year just on the ASHP. So at 30p a unit. It’s not cheap. Also used 3 tonne of logs!!
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