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My sister’s new ASHP install was costing her a tenner a day this last week.
Easily done! I turned ours on during the cold spell last week and it was closer to £13 for a days electric.
Don't make such big changes, go for a couple of degrees and leave it for a few days, ideally in cold weather.
For those of you who've had an ASHP fitted, did they make much mess? Also how many fitters were on the job?
Sorry I haven't read the whole thread.
We had 4 fitters (4 vans) on site for 4 days then 2 for 2 days. They had messed up during their survey day so basically replumbed the whole house. They expected 5 days max. Weren't too messy although I had to take up carpets later to improve the way they had refitted the boards and I have to patch some walls where they channeled out to fit additional rads, that was expected so no complaints. Our house was almost all 8mm microbore so had to be ripped out, we expected the inconvenience so no problem. If you have larger bore piping it may not be necessary but you may need additional radiators after the heat loss calcs are done.
It all depends on who is fitting it. If I was doing it, there’d be little mess, and what there was would be cleaned up every day. I work on my own, so take longer fitting it, changing from a gas boiler to a ASHP would take me, typically, 5 days, with a few rads changed too. If its a full pipework change, easily 10 days work.
I’ve read reports of others doing it in 2 days.
Octopus are now offering in our area. It gave me a flat rate of £3000 after the grant, regardless of what extra work needs doing.
On the one hand this is great, but I am planning to change the rads myself and I'm fairly sure I won't need anything else. I'd that's the case I don't want to pay the flat rate. I think I'll contact some local installers. I want to get it to come in under the £7500.
Just starting my third winter with an ASHP, still like it 🙂
I've been planning to replace rads, I did the central areas of the house last year, now I want to do the living spaces. I've been working on making them slightly wider and double panel which will roughly double the area. This will make the current boiler much more effective and efficient. However the rule of thumb seems to be that for a heat pump you want 2.5x the area.
However, I think that the original rads were oversized when run at 80C, because the house was really warm. Even as they are I can run the boiler at 55C or even 50C when it's mild and 60C when it's cold. That's a dT of around 40C. If I halved that, that would mean a flow temp of 40C in the coldest conditions we see would be enough to heat the house - therefore suitable for a heat pump. However there's a couple of caveats to that calculation. The radiator isn't the same temperature all the way across, so by doubling the area you're not really doubling the heat output. However I'm more than doubling the area, but how much heat is output depends on the flow rate, so I'm not really sure how much extra heat I'll be able to get.
The other thing to consider is that even at 55C in mild conditions the heating warms the house in say, 30 mins, and then stops for an hour or so. So in theory a heat pump could run at even lower temps for longer or even continuously, and still heat the house. And at the lower temps it could be very efficient and therefore cost less than gas (which is what I want).
I don't want to replace these rads and then have to do it again for a heat pump install in the future. But the rads I am choosing now are the biggest I think I can fit in the spaces we have so.. dunno.
Coincidentally Octopus just called me back to follow up on the quote I requested. She said that they would come and do a survey to verify what you actually need, and if rads didn't need changing that would knock the price down. She also said I could send photos of possible locations for it.
This is great service from Octopus, they have an actual knowledgable person contact you and provide follow-up through the process rather than a call centre drone. You don't have to commit after the survey which is great.
Octopus have come back with £2,400 after the grant, given that we don't need any radiators.
My sister’s new ASHP install was costing her a tenner a day this last week.
I visited my dad on Sunday and that was the cost per hour showing on the IHD for his electric panel radiators! He pooh-poohed the ASHP suggestion saying it was too expensive! It wasn't that cold in Peterborough on Sunday hopefully there won't be a fierce winter this year.
Hmm, that quote does not include £800 worth of scaffolding 🙁
Hmm, that quote does not include £800 worth of scaffolding ?
Weird, it was included in mine.
They just called me back to say that they'd waive it...
We had a heat geek survey on Monday and tomorrow have the octopus one. Fairly certain we won't be using octopus as I don't want the rads they will supply (unless I did these first). HG losses were calculated at just over 10kW at -1 (south coast, 21deg room temp). That needed 2 rad changes as apparently the modern column radiators we have are quite beefy.
Hmmm Octopus came up with a massively different 15kW loss (though the surveyor could not tell me at what internal/external temps that value is for)! Definitely no HP from octopus as they don't offer a model with a large enough output.
got a lass at work who's just bought a 3 bed semi and needs a full new GCH instal.
shes been quoted £10,000 for the boiler and rads.
shes also been quoted £9,500 for heat source instal (after the grant).
she doesnt know anything at all about them, efficiency, longevity, reliability etc, so is there a rule of thumb to work to here?
if its a total new instal would she always be better going for heat source over GCH?
are the monthly running costs going to be slightly better for the heat source pump?
another consideration is that if she had this done then she could cap her gas off which would save monthly standing charges.
she has had the loft done with decent insulation and is having new windows and doors so the insulation should be pretty decent.
cheers
If she needs a whole new system seems like an ideal time to look at a heat pump.
End of our first winter with an ASHP. 4 bed detached. Really happy. Run the house at 18c and allow up to a 2c drop overnight. House is always warm (assuming you feel warm at 18c, which we do) loads of hot water and bills over the winter lower than last winter (of course every winter is not the same) our boiler was very old so probably less efficient than a modern one.We also have PV and a battery so use Octopus Cosy tariff.
If she needs a whole new system seems like an ideal time to look at a heat pump.
agreed, thats where shes at now, looking into it.
i know theres a few of you on here that are pretty savvy about them so thought id ask about considerations that she may be unaware of.
so theyre pretty decent economy wise then and reliable. she realises that she'll need a water tank too, and ill pass on the info about the octopus tariff.
thanks
just thinking, as its looking like a good idea to press ahead with it, is there actually a situation where its not a good idea when starting from scratch?
3 bed semi
Same here - be interested to know what Octopus say. I had no room for the bloody water tank!
Mine goes in next week. I feel faintly sorry for the oil boiler which after 15 years of nearly faultless service is now running on an interesting mixture of sludge, water, leaves, kerosene, and used cooking oil. One end of the tank is propped up on bricks to get the last bit of oil out.
Mine goes in next week
@Flaperon so will you be on a specific tariff for heat source? octopus cosy for instance?
Run the house at 18c and allow up to a 2c drop overnight. House is always warm (assuming you feel warm at 18c, which we do) loads of hot water and bills over the winter lower than last winter (of course every winter is not the same) our boiler was very old so probably less efficient than a modern one.We also have PV and a battery so use Octopus Cosy tariff.
I'll chop and change, I think. I have solar and 10kWh of batteries, but generation from late November through to early February is close to zero (east/west facing). So when there's no generation probably Cosy Octopus, and for the rest of the year Intelligent Octopus Go (this means I can do hot water cheaply and the heat pump should be able to run off solar and battery combined.
Almost certainly it'll cost more than oil, but I didn't go down the heat pump route for cost saving.
I've been looking into heat pumps.
From what I can tell air-to-air heat pumps maybe a better idea, even without the grant (due to ability to run as air-con in the summer) as they don't require replacing all the plumbing and radiators.
Has anyone got any experience with them?
You'll still need something for hot water, and each indoor unit will need two pipes + cable running to it or a pretty large air duct. Sitting under a room temperature draft is also quite unpleasant if you have wall-mounted units.
I've been looking into heat pumps.
From what I can tell air-to-air heat pumps maybe a better idea, even without the grant (due to ability to run as air-con in the summer) as they don't require replacing all the plumbing and radiators.
Has anyone got any experience with them?
They are a better idea in only a small subset of properties.
A typical house needs hot water, A-A doesnt, typically, do that (there may be some units available that do, I only deal with 3 makes of HP). A-A is instant heat, well, less than 10 minutes, whereas A-W takes longer. A-A needs a ~1 meter x 400mmx400mm unit attached in each room you need heat in. A-A does need piping fitted from the outdoor unit to each cassette unit in the property for the refrigerant liquid..
Small 2/3 room houses could be suitable for A-A, as well as areas with intermittent heating, such as village halls, churches etc, but a typical 3 bedroom 6 room+ house would not be the best use for A-A, add in the water heating requirements, and a standard A-W HP would be a better solution. If you need cooling, then a split unit A-W HP could be suitable, but you’d need to fit non-standard radiators to allow the cooling fucntion to work, and it wont really work with UFH, as the cooling causes the floors to get wet with condensation.
is there actually a situation where itsnot a good idea when starting from scratch?
I have a 3 bed semi, 1930's ish. I fitted a fujitsu multi split heat pump with three ceiling units in the upstairs rooms. Mainly for the air con to help sleep on the two night summer we have every year. Two of the three rooms are occupied. I also knew I could use them for heating so trialled them this year. I kept the wet combi system running downstairs and only used the a2a upstairs. I like it that much I'm ripping up my suspended floor in the living room and insulating properly and fitting 3 consoles downstairs off another multi split, most likely Toshiba this time. Running costs are comparable with gas boiler as far as I can tell at this stage. Gutted that I had to repair the PBC in my 25 year old Baxi 105e last week, I was hoping to throw it in the bin this year. I'll likely fir a mixergy tank with heat pump next year now too.
For context I also have 20kwh of battery storage, 3.6kw E/W solar on the roof and use a Kia EV6 and a SEAT Mii, both electric. I also make use of Octopus Intelligent Go.
EDIT to mention that good placement of the units is important, they were all sited so no direct movement of air was can be felt.
The level of insulation doesn’t matter as it is the same for any heat source. How you deliver the heat is more important. A poorly insulated house will require more heat input, a kW delivered by a gas boiler is no different from one delivered by a heat pump. What is different is the size of the radiator required to deliver that kW to the room.
You also don’t need a split unit to deliver cooling.
I like it that much
Yep, it was a winter with a tiny split-system air to air heat pump upstairs that convinced me that the oil boiler could finally go.
The level of insulation doesn’t matter as it is the same for any heat source. How you deliver the heat is more important. A poorly insulated house will require more heat input, a kW delivered by a gas boiler is no different from one delivered by a heat pump
Mm no I don't think this is true. Your gas boiler is burning gas to heat water which flows through your radiators. The hotter the water, the more heat comes from them. The more heat that comes from the rads faster your house heats up. If you put in twice as much gas, you put in twice as much heat to that water and your house heats up nearly twice as quickly - the efficiency drops a bit, say 10%
This is totally not the case for heat pumps. The heat doesn't come from the electricity, it comes from the air outside. The less heat outside, the more electricity required to bring the same amount of heat inside. The hotter you want the water, the more energy is required to move more heat inside into the water. However, to move twice as much heat doesn't require twice the electricity, it might require four or five times the electricity. So if you want your house to heat up twice as quickly you might use up 5x as much power. Conversely, if you run the water half the temperature , you can heat your house half as quickly but you might use a fifth the power. Therefore, if you let your heating run twice as long at a cooler temperature, you save huge amounts of money. This is not true for gas.
So lets say your house leaks 10kW of heat on a cold day. You can put in 10kW and it stays the same temperature. Some gas boilers can run that low on a continuous basis, but most can't. So we are used to having our boiler come on, put in 20kW of heat until the place warms up and then turn off again. This is fine for gas, but for a heat pump we want to run as cool as possible so we are only putting in 10kW. With gas, if we insulate so that our house only leaks 5kW, we will run at 20kW to get the house up to temperature, but you will halve your cost because you will go twice as long between burns.
With a heat pump, pre-insulation you would run at 10kW output all the time to keep your house warm, this would take maybe 5kW of energy. If you then insulate, you would run at 5kW output which might only take 1kW of electrical power, so your costs would drop to a fifth of their previous number.
Heat pumps run hot can be 200% efficient, run cool they could be 500% efficient. Meanwhile a gas boiler is at best 100% efficient. The key point is that in the UK electricity is about 3x the cost of gas, therefore you need to hit that 300% number if you want your heat pump to be cheaper than gas.
I think you completely missed the point molgrips.
If you put in twice as much gas, you put in twice as much heat to that water and your house heats up nearly twice as quickly - the efficiency drops a bit, say 10%
This statement is a contradiction. You don't put heat in you put energy in. If the efficiency drops then your not putting the same amount of energy into the water per unit of input energy, therefore twice as much gas != twice as much energy in the water.
No one said anything about running the HP hotter. If there is sufficient emitter output then the heat pump could still operate at the cooler higher efficiency and output the required 10kw of heat. Would it be better with more insulation, undoubtedly but that's was not what bear was saying.
You don't put heat in you put energy in
You put heat into the water that circulates around your house through the rads. That heat either comes from burning gas or using electricity to suck it in from outside.
There is a finite practical size for radiators. Once you hit that, the temperature you need to run at (and hence the efficiency of your system) depends on the insulation of your house. And whilst this has a small effect on the efficiency of your gas boiler, it has a huge effect on the efficiency of your heat pump.
If the efficiency drops then your not putting the same amount of energy into the water per unit of input energy, therefore twice as much gas != twice as much energy in the water.
Yes but the efficiency of a gas boiler doesn't change that much if you run it at hotter temps - you might go from 100% to 90%. That number may be different for different boilers, but heat pumps could be half as efficient or worse when run hotter. Crucially, they could be on the wrong side of that 300% number which is the break-even point where you start to save money. It's crucial because most people don't care how their house is heated but if you persuade them to install a heat pump for the sake of the environment* then they don't want to be paying any more than they currently do.
* Even when run inefficiently the annual CO2 output of a heat pump is much less due to the amount of renewable energy in the mix.
a typical 3 bedroom 6 room+ house would not be the best use for A-A, add in the water heating requirements, and a standard A-W HP would be a better solution
Interesting @alanl - can I ask why? The reason I'm enquiring is that my house uses gas powered blown warm air heating (Johnson and Starley), a system we're very happy with unlike most who've experienced this sort of thing but it has 2 pilot lights, is non-condensing and as a result is fairly inefficient. It also means we have no radiators at all in the house and certainly no plumbing.
I'm looking at replacement in the next few years and came to the conclusion the best replacement was Air-to-Air:
- There's air ducts all over the house that would be useful for A/C piping, so access for lines to the internal units should be relatively easy as there won't be the need for cutting floorboards
- No need to find space for radiators
- Added luxury of being able to cool as well as heat
Downside - no hot water heating, but then I have Solar Thermal and an immersion heater (and EVs so could heat water overnight cheaply) so that's a secondary issue for the moment.
Molgrips - your heat pump doesn't use 10kW worth of electricity, if it did it would be outputting between 30 - 40kW.
And you are totally missing the weather compensation aspect of heat pumps.
A kW is a kW per hour regardless. Improve the insulation it will be the same for all fuels, you may argue it would be more beneficial for a heat pump as you will be able to run lower flow temps thus increasing the efficiency over a gas boiler more, but to say they don't work in older properties or uninsulated properties is one of the big myths of heat pumps.
Fridges still work in the simmer after all......
a typical 3 bedroom 6 room+ house would not be the best use for A-A, add in the water heating requirements, and a standard A-W HP would be a better solution
Interesting @alanl - can I ask why? The reason I'm enquiring is that my house uses gas powered blown warm air heating (Johnson and Starley), a system we're very happy with unlike most who've experienced this sort of thing but it has 2 pilot lights, is non-condensing and as a result is fairly inefficient. It also means we have no radiators at all in the house and certainly no plumbing.
Yours is not a typical house! If you have a way of getting the piping to the indoor units, it could be fine, and an easy install. I dont know of any AC units that use your existing ducting to blow the air through, but there may be one available, it isnt something I’ve ever looked at for long, as blown air heating is very rare in the UK, in fact I’ve only ever worked on one in the last 20 years.
Afaik in the USA they use the same ducts for heating and cooling, many of which are old, even Victorian.
Molgrips - your heat pump doesn't use 10kW worth of electricity, if it did it would be outputting between 30 - 40kW.
Yes this is the entire point of my post - the 10kW figure refers to output.
With a heat pump, pre-insulation you would run at 10kW output all the time to keep your house warm, this would take maybe 5kW of energy
Also
A kW is a kW per hour regardless
Do you mean input or output? They aren't the same for all fuels because the efficiency is different. 10kWh of gas used to heat your home might make it warm, 10kWh of electricity used to heat the same home via a heat pump would make it absolutely roasting, so clearly not the same result! You know how they work, I know how they work, not sure what we're arguing about.
to say they don't work in older properties or uninsulated properties is one of the big myths of heat pumps.
They will certainly heat your house, but the big question is that of cost. Most customers don't want to pay twice as much for their heating, and a badly planned installation could work out much more expensive than gas for the reasons I outlined above. That's why insulation and larger emitters are crucial to the main question of whether or not it's cheaper than gas.
We have A to A in our 3 bed semi. All the ducting is in the loft and its linked to MVHR system (Mitsubishi Losnay) for heat recovery and air filtering.
We mostly use this for cooling in the summer (our house gets proper mafting due to big windows).
It also does heating, but as the vents are upstairs (in all the bedrooms) any heat produced tends to heat upstairs but not downstairs. When used for cooling its fine as the cool air sinks and cools the whole house. Ours was installed by Cactus Mechanical in Leeds (they also did Brudnell social clubs heating system).
Using 20kW of gas that heats your house in half the time is the same as using 10kW for double the time. It should be kW/hr.
Heat is energy.
And that is the whole point of a heat pump, designed correctly it will be as cheap if not cheaper than a gas boiler for nearly every property.
My heat pump installation has been cancelled two days before the start date after the electrician decided that you can't have a heat pump together with a solar PV / battery setup and car charger.
80A fuse not sufficient, apparently. Considering they did a load test six months ago and didn't think it was a problem then I'm not impressed.
Garage full of heat pump equipment to be collected and I need to repair all the holes I was asked to cut exposing pipework. At least I didn't do as they asked and pull the oil boiler out prior to the installation.
And that is the whole point of a heat pump, designed correctly it will be as cheap if not cheaper than a gas boiler for nearly every property.
That's exactly what I've been saying this whole time.
See my post above. Most homes will need to keep their gas connection, you can't have any other significant loads in the house.
Heat pump: 30A
Immersion heater: 16A
Hob: 32A
Oven: 13A
Total 91A. This is the maths Northern Powergrid used to refuse my heat pump application.
So you need to keep gas in order to cook. I'd have said that this argument was utter bollocks until I found out the hard way yesterday.
That's really strange as I gave a heat pump, solar, inverter, car charger, two ovens, induction hob, and an immersion heater for my hot water tank. It all works fine. I do have more distribution boards than I know what to do with (5 at last count), but no indication that the system couldn't be installed. It has been running for coming on a year now and has saved me about 150 a month on average. That's 40 more than my 12 year interest free loan to get it all installed. Instant payback in my head.
We cut off our gas supply too.
By the way, my ashp is a propane based unit and I never got a COP of less than 4.2 throughout the winter when it has been darned cold here in Scotland. House is warmer than I had it with gas central heating and zones, but still saving money all year round. I picked propane as I am an engineer and did my sums before buying. I'd need to be down to something like -15C for extended periods (days) for the ashp to cost more to run on those days than my previous gas ch. That isn't likely even here in Scotland. Even then, I'd be saving every other day of the year. Yes the propane unit cost about 1k more than an r32 unit, but I reckon that will pay back within the 1st 2 years.
All units are due to become R290 soon.
all new heating systems MUST be designed with a maximum flow temperature of 55 deg. C.
What will ruin it is companies who do poor installs or the likes of Octopus who pick the low hanging fruit as I suspect most of their installs are run at cost at best, but the sell energy.
We got our gas meter removed this week.
Interesting chatting to the Octopus engineer, they recruited like hell in 2024 but have since laid off some folk due to economy/market conditions.
We are chuffed with our Daikin. Savings depend very much on tariff and in our case solar pV and 12kWh batteries helps massively on cost saving.
Octopus started on Monday with the install, they're mostly done. All the crappy old pipes and noisy valves have been replaced and the new install looks far higher quality. There's going to be all sorts of new gadgets and digital readouts for me to pore over, which is good. The new HW cylinder is only slightly bigger than the old one but they've installed it at the back of the airing cupboard rather than the front, which is good as it releases plenty of space.
There are two more consumer unit type boxes on the side of the house - no idea why. But it's looking good so far. I'd recommend having the install done in summer - they originally wanted to do it in Feb which would have made no sense as the heating and HW have been off for three days and the doors are all open where they come and go.
I'm not having the meter removed yet as the hob I want is another £500 on top of the heat pump cost, so it'll wait.
Had my gas meter removed last year. It was removed by Octopus, then had Centrica come round and check that it had been capped off ok. Then a few months later they came and dug up the road outside my house and capped the supply to the house off. A bit overkill, but they insisted they have to do it by law. Didn't cost me anything, though.
Ah, good. I was worried that I'd have to pay if I didn't have it done at the same time as the HP.
Some energy companies charge to remove your gas meter. Octopus don't, or didn't when i had it done.
We've just had our gas capped off. The new induction hob was fitted (got an ex kitchen showroom which saved a lot of money).
Next is to save up for solar.
There have been some unexpected costs eg having to buy induction hob compatible pans, but it'll be worth it to feel I'm helping the environment.
I'll do the hob in a few months probably.
The heat pump has been spun up but it needs proper commissioning tomorrow. It ran for a while and a fun side effect is that it blows loads of nice cold air out of the front of the unit so you can stand there and get cool on a hot day.
I'll do the hob in a few months probably.
The heat pump has been spun up but it needs proper commissioning tomorrow. It ran for a while and a fun side effect is that it blows loads of nice cold air out of the front of the unit so you can stand there and get cool on a hot day.
On a hot day, can't you run the heat pump the other way, and pump cold water through the radiators to cool the house?
Yes, but radiators aren't designed to cool air, so not very efficient.
There have been some unexpected costs eg having to buy induction hob compatible pans, but it'll be worth it to feel I'm helping the environment
No heat pump here yet, on the to do list, but we swapped out our gas hob for induction some years back. I cannot imagine cooking on gas now.
1 so much easier to clean.
2 so much control of temperature.
3 really fast to boil a pan of water.
4 so much less moisture in the kitchen without gas combustion, really.
5 yes, much nicer to be able to use renewables either from the grid (yes, I know it is a mixture) or from our own solar/battery set up.
On a hot day, can't you run the heat pump the other way, and pump cold water through the radiators to cool the house?
Yes, and some units support this, but as said radiators don't really work well for this. You'd get loads of condensation on them. But it did occur to me that you could have a blower unit fitted, and some automatic valves that divert the flow to them instead of the rads whenever you want cooling rather than heating.
EDIT I can't help myself. What you need is a water-to-air heat exchanger. In my case, the pipes from the ASHP go up the wall into the loft before coming down into the airing cupboard. If I could find a suitable heat exchanger I'd divert the flow from the ASHP into the heat exchanger then I could run normal AC ducts down to the rooms. I'd consider it except that my ASHP does not do cooling - good thing, really 🙂
EDIT 2: Daikin have you covered: https://www.daikin.co.uk/en_gb/residential/products-and-advice/product-categories/emitters/heat-pump-convector.html
If you really want air conditioning, an air to air heat pump works, but you need to put ducting in your house for the air. Tim and Kat's Green Walk on youtube explains it:
Heating with A2A - my A2A heat pump tips
I think ducting could be pretty easy, it could go between the ceiling and floor, and in the risers that the toilet pipes go down. Might have to expand them a bit but ours are already quite large.
Today the HP came on to top up the hot water at 3pm. The current electricity generating mix is only 5.7% gas, and I'm using about 1/5 as much electricity as gas so there's an almost 99% reduction in the amount of CO2 generated. That's not bad, although it won't stay like that of course. Today is very sunny and quite breezy.
Well the heating has been on - possibly didn't really need it but I wanted to try it out. Given it's not particularly cold, the software has compensated for that and runs the HP at super low flows and temperatures. Basically the rads are just about lukewarm at the top - but the house is still fine even in the mornings, because it's got the timing right. In fact, the house is 20C or thereabouts all day, and we haven't been able to even tell what it's doing unless I actually go in and check. I'm highly impressed. It's using maybe 3-500W when running as far as I can tell from the home consumption, and currently about 2kWh a day or 50p