This topic has been archived, and won't accept reply postings.
Not something I'd thought of (many more pressing projects) but the wife got a cold call from a local fitter who convinced her of great savings.
Next, I'm called up to arrange a visit to assess our property for the likely benefits.
Felt a bit pushy so my inclination is to tell them to shove it.
Anyone have / considering a ground-source or air-source heat pump for heating? Some government subsidy scheme, I believe.
What's the outlay? What's in it for me? And them?
Next, I'm called up to arrange a visit to assess our property for the likely benefits.
Felt a bit pushy so my inclination is to tell them to shove it.
Anyone have / considering a ground-source or air-source heat pump for heating? Some government subsidy scheme, I believe.
What's the outlay? What's in it for me? And them?
In reply to Just Another Dave:
Plenty info online, but I'll say both work very well in the right house . A fair proportion of UK stock don't have the insulation to do the outlay justice.
Plenty info online, but I'll say both work very well in the right house . A fair proportion of UK stock don't have the insulation to do the outlay justice.
In reply to Just Another Dave:
I've considered air-sourced heat pumps. Technically a nice solution but unjustifiable for me at the moment for a variety of reasons. No idea what subsidies are available, they're constantly changing anyway. Upside is it's efficient and can be run on renewable energy. Downside is it's not a like for like swap with a gas boiler if you want to really see the efficiency benefits it needs to be part of a broader system upgrade. They're not cheap, they need space and the air-source units aren't silent. Ground-source will necessitate some trenching or drilling.
There's a section in Without Hot Air on the relative technical merits of different heating systems, I think it's this chapter but you might have to look a round a bit http://www.withouthotair.com/c21/page_140.shtml
jk
I've considered air-sourced heat pumps. Technically a nice solution but unjustifiable for me at the moment for a variety of reasons. No idea what subsidies are available, they're constantly changing anyway. Upside is it's efficient and can be run on renewable energy. Downside is it's not a like for like swap with a gas boiler if you want to really see the efficiency benefits it needs to be part of a broader system upgrade. They're not cheap, they need space and the air-source units aren't silent. Ground-source will necessitate some trenching or drilling.
There's a section in Without Hot Air on the relative technical merits of different heating systems, I think it's this chapter but you might have to look a round a bit http://www.withouthotair.com/c21/page_140.shtml
jk
In reply to jkarran:
Thanks jk, that website is just the kind of info I need more of.
Still really not sure....
Thanks jk, that website is just the kind of info I need more of.
Still really not sure....
1
In reply to Just Another Dave:
I think you need to be really careful with this. In theory there are energy savings to be made, so a payback period can be calculated. However, it seems that it's not guaranteed to work out this way. My Dad had an air source heat pump installed a few years ago. IIRC all it did was provide hot water, and it struggled to do that at all effectively: one decent bath would leave the house with no hot water for at least an hour afterwards. What jkarran says about it not being a simple plug-in solution probably goes a fair way to explaining this. I suspect that if the installer is just after the work, and trying to tempt the householder with subsidies (which aren't by any means secure) then it's a bit of a lottery as to whether they'll actually do a worthwhile job.
I never buy stuff from cold-callers anyway. There are probably plenty of people in your area who would jump at the chance to sell you a heat pump: if you're really interested, speak to three or four of them to try to get a balanced view, rather than just going with the one who picked your name out of the phone book/off the electoral roll.
I think you need to be really careful with this. In theory there are energy savings to be made, so a payback period can be calculated. However, it seems that it's not guaranteed to work out this way. My Dad had an air source heat pump installed a few years ago. IIRC all it did was provide hot water, and it struggled to do that at all effectively: one decent bath would leave the house with no hot water for at least an hour afterwards. What jkarran says about it not being a simple plug-in solution probably goes a fair way to explaining this. I suspect that if the installer is just after the work, and trying to tempt the householder with subsidies (which aren't by any means secure) then it's a bit of a lottery as to whether they'll actually do a worthwhile job.
I never buy stuff from cold-callers anyway. There are probably plenty of people in your area who would jump at the chance to sell you a heat pump: if you're really interested, speak to three or four of them to try to get a balanced view, rather than just going with the one who picked your name out of the phone book/off the electoral roll.
2
In reply to Martin W:
That was absolutely my gut feelings too.
Just wondered if anyone had direct experience or knowledge, or if it really is well worth looking into (sometime). Still planning to tell this particular chap to fudge right off though.
That was absolutely my gut feelings too.
Just wondered if anyone had direct experience or knowledge, or if it really is well worth looking into (sometime). Still planning to tell this particular chap to fudge right off though.
1
In reply to Just Another Dave:
Mrs RR has invited sales people round to the house a couple of times and it always follows the same formula; the scare story, the price, the special reduction if we introduce a neighbour and finally the phone call to the boss who authorises a special discount if you sign up now.
Last time was Safestyle who wanted something like £5000 to replace our soffits with plastic that costs around a fiver a metre, Before that was somebody selling a Rainbow vac for an equally ridiculous sum, again thousands.
Mrs RR has invited sales people round to the house a couple of times and it always follows the same formula; the scare story, the price, the special reduction if we introduce a neighbour and finally the phone call to the boss who authorises a special discount if you sign up now.
Last time was Safestyle who wanted something like £5000 to replace our soffits with plastic that costs around a fiver a metre, Before that was somebody selling a Rainbow vac for an equally ridiculous sum, again thousands.
3
In reply to Just Another Dave:
I'd treat a cold caller selling stuff with extreme caution regardless of the product. They're almost certainly not the best people to design a system for you or to fit it. If you wanted to do it, get 3 different MCS certified installers to visit, discuss and quote.
I'm going to put an air source heat pump in in parallel with the oil boiler, but not until significant insulation works are compete. A head pump is much lower power than a comparably sized and priced boiler, so you need more time to build up temperature, which means more insulation is needed to stop the heat getting out in that time.
They cost a fair amount in electricity which has come as a shock to quite a few people who've had one fitted - miss selling by cowboy installers and/or financiers probably..
They tend to run cooler than a boiler so ideally you want underfloor heating, giant low-temperature radiators or forced airflow radiators as normal high rads won't be able to transfer the heat from the water into the room fast enough leaving the return water to hot, and the energy gains of a heat pump depend on a cold return water temperature.
I don't expect the heat pump to save me money, I'm doing it at expense to reduce our usage of oil and give us redundancy in heating. It's going to be pared with ~8kWe of solar PV with load-shifting batteries, with the heat pump taking precedence over grid export for spare solar power.
This also is not a good return on investment - the whole thing is estimated to give cost savings at ~1% ROI.
Ground source pumps - a lot of digging; air source pumps - might piss the neighbours off especially as bearings degrade over time.
Edit: the Renewable Heat Incentive may pay you for heat produced with a heat pump under the MCS. I won't claim anything under feed in tarrifs as I personally see them as a regressive tax I don't want to profit from. Also, if you don't go MCS and do it yourself you save an amount somewhat similar to the feed in revenue. Although some things are only "permitted development" in a planning sense if done to MCS guidelines...
I'd treat a cold caller selling stuff with extreme caution regardless of the product. They're almost certainly not the best people to design a system for you or to fit it. If you wanted to do it, get 3 different MCS certified installers to visit, discuss and quote.
I'm going to put an air source heat pump in in parallel with the oil boiler, but not until significant insulation works are compete. A head pump is much lower power than a comparably sized and priced boiler, so you need more time to build up temperature, which means more insulation is needed to stop the heat getting out in that time.
They cost a fair amount in electricity which has come as a shock to quite a few people who've had one fitted - miss selling by cowboy installers and/or financiers probably..
They tend to run cooler than a boiler so ideally you want underfloor heating, giant low-temperature radiators or forced airflow radiators as normal high rads won't be able to transfer the heat from the water into the room fast enough leaving the return water to hot, and the energy gains of a heat pump depend on a cold return water temperature.
I don't expect the heat pump to save me money, I'm doing it at expense to reduce our usage of oil and give us redundancy in heating. It's going to be pared with ~8kWe of solar PV with load-shifting batteries, with the heat pump taking precedence over grid export for spare solar power.
This also is not a good return on investment - the whole thing is estimated to give cost savings at ~1% ROI.
Ground source pumps - a lot of digging; air source pumps - might piss the neighbours off especially as bearings degrade over time.
Edit: the Renewable Heat Incentive may pay you for heat produced with a heat pump under the MCS. I won't claim anything under feed in tarrifs as I personally see them as a regressive tax I don't want to profit from. Also, if you don't go MCS and do it yourself you save an amount somewhat similar to the feed in revenue. Although some things are only "permitted development" in a planning sense if done to MCS guidelines...
Post edited at 13:47
In reply to Just Another Dave:
I looked into them several times when I renovated my current residence and I´ ve friends with all the different sorts as well as knowing two guys who install them.
As others have said you really do need a new-build to make any sense, the heat is low-quality so you either need under-floor or wall heating to get enough surface area, both react fairly slowly. Or you go to blown air which needs huge air ducts through the house (the air transfer is low speed so the need to be pretty large.
When it gets real cold air-based systems have to use electricity to pre-heat the air, ground thermal store you need a big garden, no shade and hopefully good weather to heat it up over the summer and your gardening will suffer if that´ s important.
Bore-hole systems are probably the best but you usually have to go much deeper than you´ d think to get high enough temperatures and the local run-off is important, I live beside a river and the water table is 2m down but it´ s cold, my neighbour had to go 13m down to get enough heat. You also need to check the local rules, sometimes like here in Germany you have to pay for the heat extracted as it belongs to the local water board.
Even though I could get it done real cheap I didn´ t bother, installing a low-temperature heating system was economically out of the question.
And don´t believe a word if they say you can also reverse-cycle in the summer to cool (except air/air) as you end up with the floor covered in condensation, a friend down the road was stupid enough to pay for this!
I looked into them several times when I renovated my current residence and I´ ve friends with all the different sorts as well as knowing two guys who install them.
As others have said you really do need a new-build to make any sense, the heat is low-quality so you either need under-floor or wall heating to get enough surface area, both react fairly slowly. Or you go to blown air which needs huge air ducts through the house (the air transfer is low speed so the need to be pretty large.
When it gets real cold air-based systems have to use electricity to pre-heat the air, ground thermal store you need a big garden, no shade and hopefully good weather to heat it up over the summer and your gardening will suffer if that´ s important.
Bore-hole systems are probably the best but you usually have to go much deeper than you´ d think to get high enough temperatures and the local run-off is important, I live beside a river and the water table is 2m down but it´ s cold, my neighbour had to go 13m down to get enough heat. You also need to check the local rules, sometimes like here in Germany you have to pay for the heat extracted as it belongs to the local water board.
Even though I could get it done real cheap I didn´ t bother, installing a low-temperature heating system was economically out of the question.
And don´t believe a word if they say you can also reverse-cycle in the summer to cool (except air/air) as you end up with the floor covered in condensation, a friend down the road was stupid enough to pay for this!
2
1
In reply to Just Another Dave:
https://www.ofgem.gov.uk/environmental-programmes/domestic-rhi
Worth having a poke on here about RHI payments. As others have said, you need a really energy efficient house for it to be worth it. Solar panels works well as a complimentary installation to cover your increased electricity costs.
https://www.ofgem.gov.uk/environmental-programmes/domestic-rhi
Worth having a poke on here about RHI payments. As others have said, you need a really energy efficient house for it to be worth it. Solar panels works well as a complimentary installation to cover your increased electricity costs.
In reply to Just Another Dave:
Well thanks all, worthwhile responses.
I've had a good read around, and think the idea would be just barmy for me. (Victorian house, high on Saddleworth Moor, on steep ground with bedrock not far below, inside National Park [tricky putting anything outside the building], mains gas Aga, wood stoves, electricity only used for lighting...)
Seller's number's getting blocked!
Well thanks all, worthwhile responses.
I've had a good read around, and think the idea would be just barmy for me. (Victorian house, high on Saddleworth Moor, on steep ground with bedrock not far below, inside National Park [tricky putting anything outside the building], mains gas Aga, wood stoves, electricity only used for lighting...)
Seller's number's getting blocked!
In reply to Just Another Dave:
If you run stoves try a stove too can powered by a seebeck generator.
If you run stoves try a stove too can powered by a seebeck generator.
In reply to summo:
Or a stove top Stirling cycle fan! We don't have the vertical clearance for this, which saved me wasting some money...
http://www.stirlingengine.co.uk/d.asp?product=VULCANSTOVEFAN
> If you run stoves try a stove top fan powered by a seebeck generator.
Or a stove top Stirling cycle fan! We don't have the vertical clearance for this, which saved me wasting some money...
http://www.stirlingengine.co.uk/d.asp?product=VULCANSTOVEFAN
1
In reply to Just Another Dave:
Great stuff from wintertree as usual.
The big issue with heat pumps is that they need to be installed by people who know what they're doing, i.e. not your typical UK cowboy builder.
They will use loads of electricity of they're not sized and chosen properly. They're used all over the nordic countries and Germany and work really well. I've got an ASHP in my flat in Helsinki and it's great - quiet, incredibly cheap and reliable.
Jimtitt - you're not trying to find geothermal for GSHP you're just using the constantly warmer temp in the ground so no you don't have to dig deep at all. A couple of degrees above zero is fine and if you have running water that's brilliant as you get quick heat transfer and don't cool off your store of thermal mass.
Great stuff from wintertree as usual.
The big issue with heat pumps is that they need to be installed by people who know what they're doing, i.e. not your typical UK cowboy builder.
They will use loads of electricity of they're not sized and chosen properly. They're used all over the nordic countries and Germany and work really well. I've got an ASHP in my flat in Helsinki and it's great - quiet, incredibly cheap and reliable.
Jimtitt - you're not trying to find geothermal for GSHP you're just using the constantly warmer temp in the ground so no you don't have to dig deep at all. A couple of degrees above zero is fine and if you have running water that's brilliant as you get quick heat transfer and don't cool off your store of thermal mass.
In reply to Rigid Raider:
We had Coldseal and Safestyle in to quote for double glazing on the same day many years ago. I felt absolutely drained and vowed never to let a double glazing salesman in the house again. They tried all the tricks you mentioned, but you missed the stalling tactic from your list. The Coldseal guy asked for a glass of water, which he took over half an hour to drink.
In the end we didn't go with either of them. Safestyle quoted £12k for the job, which was with the so called 50% discount. So their full price was in fact £24k. We only paid £70k for the whole house FFS!
> Last time was Safestyle who wanted something like £5000 to replace our soffits with plastic that costs around a fiver a metre, Before that was somebody selling a Rainbow vac for an equally ridiculous sum, again thousands.
We had Coldseal and Safestyle in to quote for double glazing on the same day many years ago. I felt absolutely drained and vowed never to let a double glazing salesman in the house again. They tried all the tricks you mentioned, but you missed the stalling tactic from your list. The Coldseal guy asked for a glass of water, which he took over half an hour to drink.
In the end we didn't go with either of them. Safestyle quoted £12k for the job, which was with the so called 50% discount. So their full price was in fact £24k. We only paid £70k for the whole house FFS!
In reply to wintertree:
Yeah, same principle of circulating air, different powering mechanism.
> Or a stove top Stirling cycle can
Yeah, same principle of circulating air, different powering mechanism.
In reply to Just Another Dave:
What Wintertree said - the output of a heat pump is normally of a lower temperature than that of a boiler, therefore you need a large 'radiator' surface area to transfer enough heat into the house. They make good sense with water underfloor heating for this reason. I have heard of a badly-specced ground-source system here that literally froze the garden. The efficiency of a properly designed system is in no doubt (eg. use 1kw of electricity to pull 4kw of heat into the house), but it has to be properly designed. As to cold-callers - any decent tradesman will have more than enough work from word of mouth, anyone having to tout for business obviously isn't any good (unless something's happened in their local area to ruin the economy like a steelworks closing down etc.)
What Wintertree said - the output of a heat pump is normally of a lower temperature than that of a boiler, therefore you need a large 'radiator' surface area to transfer enough heat into the house. They make good sense with water underfloor heating for this reason. I have heard of a badly-specced ground-source system here that literally froze the garden. The efficiency of a properly designed system is in no doubt (eg. use 1kw of electricity to pull 4kw of heat into the house), but it has to be properly designed. As to cold-callers - any decent tradesman will have more than enough work from word of mouth, anyone having to tout for business obviously isn't any good (unless something's happened in their local area to ruin the economy like a steelworks closing down etc.)
In reply to wintertree:
You can buy tiny ones which are around 12 to 14 cm high.
Alternatively, I've been vaguely wondering about buying the cheapest I can find, and carefully uniformly shortening the blades, and making the stand lower to get one to fit in the space for my stove. It dawned on me you could make a card template or similar, and secure that onto each blade in turn, so they're the same shape and length after being shortened by hand with careful cutting and filing, so that when it spins it's still in enough balance.
Funny how there's so many things one 'could' be doing when a home is your own.
> Or a stove top Stirling cycle fan! We don't have the vertical clearance for this, which saved me wasting some money...
You can buy tiny ones which are around 12 to 14 cm high.
Alternatively, I've been vaguely wondering about buying the cheapest I can find, and carefully uniformly shortening the blades, and making the stand lower to get one to fit in the space for my stove. It dawned on me you could make a card template or similar, and secure that onto each blade in turn, so they're the same shape and length after being shortened by hand with careful cutting and filing, so that when it spins it's still in enough balance.
Funny how there's so many things one 'could' be doing when a home is your own.
Post edited at 17:44
In reply to ad111:
I know you aren´ t looking for geothermal, I said it´ s the run-off into the water table that´´ s important. Into my well it´ s 6°C over the winter as it is rain soaked into the fields above me which is far too low for any sort of efficiency, most air pump system would be shutting down or going into heat mode. Normal water/water systems are set to shut down when the output water gats to 2°C to prevent freezing. You need around 12°C constant flow throughout the year to operate any tandard system so you have to go deeper into the water table. A "couple of degrees above zero" doesn´ t work as when you pull the heat out of the water it freezes.
The exciting thing with air/air or air/water systems is to watch the electricity meter when they freeze up, not only are you heating your house with electricity you´ re also de-frosting the heat pump by reversing the cycle (in other words you heat up your house and the heating system steals heat by cooling the house as well to keep itself alive.)
> Jimtitt - you're not trying to find geothermal for GSHP you're just using the constantly warmer temp in the ground so no you don't have to dig deep at all. A couple of degrees above zero is fine and if you have running water that's brilliant as you get quick heat transfer and don't cool off your store of thermal mass.
I know you aren´ t looking for geothermal, I said it´ s the run-off into the water table that´´ s important. Into my well it´ s 6°C over the winter as it is rain soaked into the fields above me which is far too low for any sort of efficiency, most air pump system would be shutting down or going into heat mode. Normal water/water systems are set to shut down when the output water gats to 2°C to prevent freezing. You need around 12°C constant flow throughout the year to operate any tandard system so you have to go deeper into the water table. A "couple of degrees above zero" doesn´ t work as when you pull the heat out of the water it freezes.
The exciting thing with air/air or air/water systems is to watch the electricity meter when they freeze up, not only are you heating your house with electricity you´ re also de-frosting the heat pump by reversing the cycle (in other words you heat up your house and the heating system steals heat by cooling the house as well to keep itself alive.)
2
In reply to wintertree:
I have got a Stirling engine fan for my stove. I love it.
> Or a stove top Stirling cycle fan! We don't have the vertical clearance for this, which saved me wasting some money...
I have got a Stirling engine fan for my stove. I love it.
1
In reply to Martin W:
I am completely reliant on a multi fuel stove for my heating and hot water (normally burning a mixture of soft and hard woods). It takes a while to get the house up to temp but otherwise does a fine job. Even with the fire burning on a moderate setting would probably take an hour or two to reheat a tank full of water.
Looking online it seems that it requires about 3.5KW to raise a tank full from 20C to 50C in an hour. Which to me, isn’t that shabby.
> one decent bath would leave the house with no hot water for at least an hour afterwards.
I am completely reliant on a multi fuel stove for my heating and hot water (normally burning a mixture of soft and hard woods). It takes a while to get the house up to temp but otherwise does a fine job. Even with the fire burning on a moderate setting would probably take an hour or two to reheat a tank full of water.
Looking online it seems that it requires about 3.5KW to raise a tank full from 20C to 50C in an hour. Which to me, isn’t that shabby.
In reply to jimtitt:
You can get air source heat pumps that will still work at outside air temps of -30c, efficiency is lower, so it's normal to installing something a little over engineered for the anticipated average winter temps so the efficiency doesn't fall off a cliff in Jan and Feb.
You can get air source heat pumps that will still work at outside air temps of -30c, efficiency is lower, so it's normal to installing something a little over engineered for the anticipated average winter temps so the efficiency doesn't fall off a cliff in Jan and Feb.
In reply to jimtitt:
You're right - just saying a couple of degrees above zero is fine was pretty stupid of me.
But . . .
At the time of maximum extraction (early Jan) the temperature of the ground at 1.5m under (average for a GSHP) will be between 5 and 10 degrees with the source at the inlet hovering around 3 to 6 degrees. However, this is OK so long as you have sized your ground array appropriately to the location and heat demand as you will know how much heat will be removed from the ground and you will keep the surrounding ground from freezing.
If you want references - cantor and harper, 2011 (will give you a nice graph of source temps for GSHP and ASHP, but the whole thing is huge so you might not want to read the through) as will Elkins and hunt, 2008 (their measured temps are from Falmouth so it's a little warmer there )
While in lower temperature COP does drop it doesn't mean you get poor efficiency compared with many heating systems.
In an ASHP you can get a COP of 2.5 at -15 degrees so long as you have a flow rate of around 35 degrees. In testing heat pumps have achieved a COP of 3.2 in -10 which is pretty amazing.
Anyway I'm mostly talking figures and they have next to nothing in common with most installed systems - especially in the UK. It's cool that you have one and are watching how it performs! I have an ASHP in my flat in Helsinki it pumps out air at 15 degrees all winter and it is brilliant. Uses hardly any electricity and the flat is always warm!
You're right - just saying a couple of degrees above zero is fine was pretty stupid of me.
But . . .
At the time of maximum extraction (early Jan) the temperature of the ground at 1.5m under (average for a GSHP) will be between 5 and 10 degrees with the source at the inlet hovering around 3 to 6 degrees. However, this is OK so long as you have sized your ground array appropriately to the location and heat demand as you will know how much heat will be removed from the ground and you will keep the surrounding ground from freezing.
If you want references - cantor and harper, 2011 (will give you a nice graph of source temps for GSHP and ASHP, but the whole thing is huge so you might not want to read the through) as will Elkins and hunt, 2008 (their measured temps are from Falmouth so it's a little warmer there )
While in lower temperature COP does drop it doesn't mean you get poor efficiency compared with many heating systems.
In an ASHP you can get a COP of 2.5 at -15 degrees so long as you have a flow rate of around 35 degrees. In testing heat pumps have achieved a COP of 3.2 in -10 which is pretty amazing.
Anyway I'm mostly talking figures and they have next to nothing in common with most installed systems - especially in the UK. It's cool that you have one and are watching how it performs! I have an ASHP in my flat in Helsinki it pumps out air at 15 degrees all winter and it is brilliant. Uses hardly any electricity and the flat is always warm!
Post edited at 08:37
1
In reply to Timmd:
The alternative to a stirling fan is a peltier electric one - they're about £40.
http://www.domu.co.uk/vonhaus-stove-fan
Apparently 5 blade fans are most efficient but noisy, 2 blades are inefficient, so 3 blades is the best compromise unless you don't mind the noise - I don't know how noisy they are.
The alternative to a stirling fan is a peltier electric one - they're about £40.
http://www.domu.co.uk/vonhaus-stove-fan
Apparently 5 blade fans are most efficient but noisy, 2 blades are inefficient, so 3 blades is the best compromise unless you don't mind the noise - I don't know how noisy they are.
1
In reply to summo:
Sure, my nephew would freeze otherwise as he´ s got air to water and it was below -20° last week.
BUT!!! With a COP of 1.1 at -30° it´ s hardly efficient or ecomomic compared with gas, oil, wood or pellets since electricity (here at least) costs slightly over 4 times as much per kWh as the others.
Given the need to accomodate a low-grade heating sytem into the house and the increased installation costs a heat pump needs a COP of at least 4 to break-even as an investment. The only realistic way to achieve this is brine/water systems using 10° or higher ground water.
Using my spring with water at 6° it´ s cheaper to use conventional fuels in the existing system without even considering the extra installation costs.
> You can get air source heat pumps that will still work at outside air temps of -30c, efficiency is lower, so it's normal to installing something a little over engineered for the anticipated average winter temps so the efficiency doesn't fall off a cliff in Jan and Feb.
Sure, my nephew would freeze otherwise as he´ s got air to water and it was below -20° last week.
BUT!!! With a COP of 1.1 at -30° it´ s hardly efficient or ecomomic compared with gas, oil, wood or pellets since electricity (here at least) costs slightly over 4 times as much per kWh as the others.
Given the need to accomodate a low-grade heating sytem into the house and the increased installation costs a heat pump needs a COP of at least 4 to break-even as an investment. The only realistic way to achieve this is brine/water systems using 10° or higher ground water.
Using my spring with water at 6° it´ s cheaper to use conventional fuels in the existing system without even considering the extra installation costs.
In reply to jimtitt:
totally agree on the efficiency, perhaps I misread your post as I was reply more as I thought you implied they were not any good for sub zero temps.
Yeah -20 is fine, although near the limit for any efficiency, even for the better built units or brands. Folk further north than us where it get's proper cold -30/-35c or less, tend to use either ground source, pellets etc.. (no oil or gas), many just top their house heating for the coldest months with a wood stove or electric, knowing that for the other 9 mths of the years air sourced is more than capable.
Insulation is often the answer to many heating problems. A house can be insulated for life, ie. centuries, a heating system will be replaced a few times every century.
we have a similar quandary, we use only 1 electric heater and a wood burning stove during the day, nothing at night as the heat loss is minimal and we haven't quite finished the insulation, with about 8 or 9m of external north facing wall left to go. A ground source system would simply never pay back. Fitting one air source system would only buy us convenience, save chopping wood etc.. it's unlikely to save us money. We plan to wait until all walls are done and have another winter before deciding.
> BUT!!! With a COP of 1.1 at -30° it´ s hardly efficient or ecomomic compared with gas, oil, wood or pellets since electricity (here at least) costs slightly over 4 times as much per kWh as the others.
totally agree on the efficiency, perhaps I misread your post as I was reply more as I thought you implied they were not any good for sub zero temps.
Yeah -20 is fine, although near the limit for any efficiency, even for the better built units or brands. Folk further north than us where it get's proper cold -30/-35c or less, tend to use either ground source, pellets etc.. (no oil or gas), many just top their house heating for the coldest months with a wood stove or electric, knowing that for the other 9 mths of the years air sourced is more than capable.
> Given the need to accomodate a low-grade heating sytem into the house and the increased installation costs a heat pump needs a COP of at least 4 to break-even as an investment.
Insulation is often the answer to many heating problems. A house can be insulated for life, ie. centuries, a heating system will be replaced a few times every century.
> Using my spring with water at 6° it´ s cheaper to use conventional fuels in the existing system without even considering the extra installation costs.
we have a similar quandary, we use only 1 electric heater and a wood burning stove during the day, nothing at night as the heat loss is minimal and we haven't quite finished the insulation, with about 8 or 9m of external north facing wall left to go. A ground source system would simply never pay back. Fitting one air source system would only buy us convenience, save chopping wood etc.. it's unlikely to save us money. We plan to wait until all walls are done and have another winter before deciding.
Post edited at 18:34
In reply to Just Another Dave:
When evaluating a renewable energy system, never forget to factor in your age. The majority of these systems are sold to those who are at least middle aged, these are the people with the disposable income. Ask yourself, will I be in the house or even still around to reach the payback time?
Sorry to be morbid but it is a real consideration that many overlook.
When evaluating a renewable energy system, never forget to factor in your age. The majority of these systems are sold to those who are at least middle aged, these are the people with the disposable income. Ask yourself, will I be in the house or even still around to reach the payback time?
Sorry to be morbid but it is a real consideration that many overlook.
In reply to jimtitt:
Although for many people the additional cost is worth it to decarbonise.
Personally I'd rather give the money to someone as an advance payment on my electricity, to help fund them to build more fission plant.
As I can't do that, I can decarbonise at the household level. As a bonus, missing a few years' foreign holidays to pay for it does a bit more good.
> ... or ecomomic ...
Although for many people the additional cost is worth it to decarbonise.
Personally I'd rather give the money to someone as an advance payment on my electricity, to help fund them to build more fission plant.
As I can't do that, I can decarbonise at the household level. As a bonus, missing a few years' foreign holidays to pay for it does a bit more good.
1
This topic has been archived, and won't accept reply postings.
Loading Notifications...