Air-source heat pumps - are they good/crap?
Discussion
Snow and Rocks said:
I always find it amusing when people say that an ASHP will be perfectly economical if you have a really well insulated house - feels a bit like saying a Range Rover V8 is affordable to run if you buy a house next door to your office.
Yes an ASHP might be viable in a really well insulated house but what would it cost to heat that same insulated house with a gas boiler? I'd put money on it being cheaper overall and you wouldn't have to deal with the inflexibility of the heat pump.
This 100% agree.Yes an ASHP might be viable in a really well insulated house but what would it cost to heat that same insulated house with a gas boiler? I'd put money on it being cheaper overall and you wouldn't have to deal with the inflexibility of the heat pump.
Pointless thread is pointless; it took no time at all to descend into "my ASHP flings s
te at the moon" "No, ASHP is st" The only way to find out is to ask the vendor what the monthly costs are. ASHP works fine if it's installed and set up properly in an adequately insulated dwelling. If not it can be terrible.
te at the moon" "No, ASHP is st" The only way to find out is to ask the vendor what the monthly costs are. ASHP works fine if it's installed and set up properly in an adequately insulated dwelling. If not it can be terrible.Snow and Rocks said:
I always find it amusing when people say that an ASHP will be perfectly economical if you have a really well insulated house - feels a bit like saying a Range Rover V8 is affordable to run if you buy a house next door to your office.
Yes an ASHP might be viable in a really well insulated house but what would it cost to heat that same insulated house with a gas boiler? I'd put money on it being cheaper overall and you wouldn't have to deal with the inflexibility of the heat pump.
It's not difficult to do the maths but the question is what variables?Yes an ASHP might be viable in a really well insulated house but what would it cost to heat that same insulated house with a gas boiler? I'd put money on it being cheaper overall and you wouldn't have to deal with the inflexibility of the heat pump.
Gas is circa 7p/kWh and let's say 80% efficient typically.
Heat pump running on 28p/kWh electricity is anything from 2.5-4.5 coefficient of performance.
So then you have loads of variables on the desire to maintain temperature and the cost of your electricity (be it solar, battery, off-peak etc).
There are loads of bad heat pump installations. Air to air typically has fewer causes of error, but if you poorly locate the external you will still have issues.
Evanivitch said:
It's not difficult to do the maths but the question is what variables?
Gas is circa 7p/kWh and let's say 80% efficient typically.
Heat pump running on 28p/kWh electricity is anything from 2.5-4.5 coefficient of performance.
So then you have loads of variables on the desire to maintain temperature and the cost of your electricity (be it solar, battery, off-peak etc).
There are loads of bad heat pump installations. Air to air typically has fewer causes of error, but if you poorly locate the external you will still have issues.
Yep, on paper, you can just about, if you squint a bit, make the numbers work using a high COP. Gas is circa 7p/kWh and let's say 80% efficient typically.
Heat pump running on 28p/kWh electricity is anything from 2.5-4.5 coefficient of performance.
So then you have loads of variables on the desire to maintain temperature and the cost of your electricity (be it solar, battery, off-peak etc).
There are loads of bad heat pump installations. Air to air typically has fewer causes of error, but if you poorly locate the external you will still have issues.
Once you include the much greater install cost, the tales of woe from poorly installed or specced systems and the apparent need to heat the place constantly rather than just when you actually need it then it becomes pretty obvious which is the more sensible option.
Notsofastfrank said:
I don’t see how I have, quite the opposite but I expect like most experts, you’ll be sure to have the last word. Have you actually had an ASHP in your home or are you just regurgitating sensationalist You Tubers?
I have lived in properties with them and also have enough family members and friends with them to know without any doubt that they are absolute garbage. They're basically an extremely convulted, noisy and expensive electric radiator heating system. Save yourself all the aggro and just get yourself down to Argos and buy a bunch a oil-filled electric rads. They'll be about 100x cheaper to buy and the actual running costs will be the same, without needing to remortgage your house to get your crappy heat pump install fixed when it inevitably breaks.Or just install GCH like any normal person, if you can get it where you live.
Notsofastfrank said:
The house is 3000 square feet and we pay £110 pm with the assistance of 7kw of solar panels and a 5kwh battery, without the solar/battery the cost would be about £225 a month. .
I found this an interesting number. I have an 11,000 sq ft new self build. Gas boiler ( very small ) underfloor heating and well insulated ( building regs give you no choice). The Sap calcs last week gave it epc B so very good but not a passivhaus ( which we never set out to do ).
Our gas bill is £350 per month. The house is set to 22 degrees for the day and 18 at night but never drops more than about 1.5 degrees over night and that is only if really cold.
The ground floor heating is on. The first floor only in the bedrooms in use and the top floor is all off as it does not need it on and would overheat if it did.
We looked at ground source heat pump - they wanted £90k!!! I did not look at air source as a friend has one he described as being like a jet engine when running. The cost I imagine would have been £20k plus.
Our boiler is an Atag i 140r which is £1200. Gas if you have it is a no brainer.
caziques said:
This is the issue, correct installation.
Unlike a boiler, which can basically be chucked in and it will work OK, other factors such as water flow. controls, sizing, defrosting cycles, pipe sizing, radiator sizing and buffer tanks must be considered when a heat pump is fitted.
It would be very unlikely that a heat pump will perform OK simply by replacing a gas boiler.
Essentially this. A Heat Pump requires a heating engineer to do the work on calculating heat loss and then fully designing the system like you say, especially when it comes down to pipe sizing, flow rates, rads etc. Unlike a boiler, which can basically be chucked in and it will work OK, other factors such as water flow. controls, sizing, defrosting cycles, pipe sizing, radiator sizing and buffer tanks must be considered when a heat pump is fitted.
It would be very unlikely that a heat pump will perform OK simply by replacing a gas boiler.
I don't understand why people bang the insulation drum soo much, a house with a gas boiler will still have the same heat loss if you put in an ASHP. Doesn't matter if your place loses 15kW at DOT or 5kW, gas or ASHP still have to work with the same fabric and heat loss.
I'm researching and considering one at some point, but it would be with a pucker company and I'd do all the calcs first to be sure I can check their work and design. But a good one will charge more, especially if you go for Heat Geek assured.
But last year I added the wireless outdoor temp sensor, now the gas boiler works with weather compensation, plus I will add UFH pipes under the suspended timber floor and hook the new zone valve up to the second zone input on the wiring centre and just use the whole ground floor as an additional single zone emitter (no need to upsize rads), so I can drop the flow temp further and ensure the boiler is even higher in the condensing zone. I've range rated the boiler down to circa 15-18kW (from 35kW), am about to put in a smart switch to control the HW tank immersion when I get cheap 7.5p/kWh electricity and the job is jobbed.
The boiler only modulates down to 9kW, but better to live with that and tweak the insulation and any ventilation losses first (with help from thermal camera) than throw money away installing an expensive viessemann W-200 and unvented tank for £5-6k.
Edited by -Ad- on Monday 5th February 08:33
caziques said:
This is the issue, correct installation.
Nope.The issue is that here in the UK (Caziques is from New Zealand: different climate, different economy; different construction techniques), even when they are correctly installed and operating efficiently, running costs are not significantly different from a mains gas boiler, and the mains gas boiler is more flexible.
You might speculate that the price of mains gas will rise in the future - either as a result of supply-and-demand, or because the Government increases taxes upon it - but until that happens there is no practical, economic case in favour of heat pumps if you have access to mains gas supply.
If you don't have access to mains gas supply, it comes down to what values you place on the balance between running costs versus flexibility.
Equus said:
If you don't have access to mains gas supply, it comes down to what values you place on the balance between running costs versus flexibility.
Even without a mains gas supply, oil is reasonably priced, averaging out at about ~7p per kwh and the boilers are generally simple and long lasting. The lack of any standing charge also more than covers the cost of the replacing the tank every few decades. Equus said:
The issue is that here in the UK (Caziques is from New Zealand: different climate, different economy; different construction techniques), even when they are correctly installed and operating efficiently, running costs are not significantly different from a mains gas boiler, and the mains gas boiler is more flexible.
Running costs not significantly different and running largely on renewables rather than 100% fossil would be sufficient to entirely justify the government stance on them.Snow and Rocks said:
Even without a mains gas supply, oil is reasonably priced, averaging out at about ~7p per kwh...
Yes, it is, but at that cost (and assuming a boiler efficiency of 80%) it would be about 13% more expensive than an ASHP, if you can manage to make the heat pump run at an SCOP of 3.5 (which is not impossible from a well-optimised system).My own heating system runs on oil, and that's an informed decision I've made on the basis that I'm willing to pay a slight premium for the flexibility... I live in a high thermal mass property (thermal mass being entirely different to insulation, by the way) and even at this time of year I sleep with the bedroom window open because I prefer it to be cool when I'm in bed... but I work from home and want the temperature to be ~20C within half an hour of me getting up in the morning. A heat pump would have an absolute dicky-fit if I expected it to function under such a regime, and I'm willing to pay a premium to have a heating system that's controlled by me, rather than the other way around.
otolith said:
Running costs not significantly different and running largely on renewables rather than 100% fossil would be sufficient to entirely justify the government stance on them.
The government stance is a matter for the government, of course. They could shift the economics (by taxing fossil fuels more), but for political reasons they choose not to do so.Until they do, we're left with a situation where, as you say, running costs are not significantly different (at least if you're a PistonHeads PBD, rather than living on a tight budget), but fossil fuel boilers are significantly more flexible.
Assuming I don't buy into the idea that climate change is my personal fault, why would I want to install a system that is less flexible than it could be?
-Ad- said:
I can imagine you either living in some uber contemporary box with concrete floors, stairs and dining table..... Or a cottage with bunker sized walls.
I suffer from a fairly extreme case of Cobbler's Son syndrome, I'm afraid: I DGAF about the property I live in myself - never have. Equus said:
otolith said:
Running costs not significantly different and running largely on renewables rather than 100% fossil would be sufficient to entirely justify the government stance on them.
The government stance is a matter for the government, of course. They could shift the economics (by taxing fossil fuels more), but for political reasons they choose not to do so.Until they do, we're left with a situation where, as you say, running costs are not significantly different (at least if you're a PistonHeads PBD, rather than living on a tight budget), but fossil fuel boilers are significantly more flexible.
Assuming I don't buy into the idea that climate change is my personal fault, why would I want to install a system that is less flexible than it could be?
Equus said:
My own heating system runs on oil, and that's an informed decision I've made on the basis that I'm willing to pay a slight premium for the flexibility... I live in a high thermal mass property (thermal mass being entirely different to insulation, by the way) and even at this time of year I sleep with the bedroom window open because I prefer it to be cool when I'm in bed... but I work from home and want the temperature to be ~20C within half an hour of me getting up in the morning. A heat pump would have an absolute dicky-fit if I expected it to function under such a regime, and I'm willing to pay a premium to have a heating system that's controlled by me, rather than the other way around.
We also sleep with bedroom winter open. But we close bedroom door and close bedroom window when we wake. The warmth from rest of house flows in. We don't have a heatpump but I'm trying to work the boiler as close to one as I can. However it's likely we'll get a Air to Air system in the next hear or so instead of a Air to water system..otolith said:
Indeed, the usual mechanism is to use regulatory and fiscal powers to align the individual's options to policy objectives. If, acting rationally, you don't act as they would wish, that's really their fault. Not that everyone sees it that way when that is actually done and the option they prefer is made unattractive or unavailable.
It depends whether we are talking about 'now' or 'in future'.I think we've been given fair warning what the future holds.
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff