Air Source Heat Pump: Payback Period

feckoffcrow

Just wondering what is the payback period on air source heat pumps?

I have an existing oil based central heating system and wondered how easy it would be to augment heat supply via a air source heating system?

Does anyone have any experience with this? I know that ground source heat pumps are not considered to be worthwhile because of the electricity requirement. Is it fair to say that the electricity requirement for air source systems is considerably less??

746watts

I have neighbours who added an extension with underfloor heating and installed one of those systems. It was costing a fortune on ESB and they quickly applied for a night saver meter but the ESB costs are still a pain, although less now. Neighbours don't recommend putting one in from their experience.

What about installing solar panels and increasing your attic insulation levels instead? They are more cost effective to run with much shorter payback times.
I have a solar panel system and put in 9inch of insulation on top of the 6inches in the attic. I've noticed a huge improvement in heat retention. Only need 700lt of oil for the whole year to heat rads (1800ft2 house) and have no immersion nor oil on to heat water most of the year.

feckoffcrow

Hi 746Watts. Have been doing some reading up today on previous boards.ie threads and the story is similar to what you have suggested. However, just checking it out in case. IF the running costs can be kept down, then it wouldn't be long in paying for itself due to the small capital cost. I would be looking at integrating it with the existing oil/rads system - and whilst i understand this presents some difficulties, apparantly its possible (don't know exactly how yet). So, oil can be used when it becomes uneconomical to use air pump.
By all accounts these systems are viable in Sweden but its the issue of them icing up here thats a difficulty. However, have come across someone who has covered their system with some kind of diy housing to prevent this - and the need to expend energy on keeping the unit ice-free. IF this is the case, then maybe it can be implemented viably??

As regards insulation - your quite right. Its a no brainer - topped up this time last year and will probably get a couple of rolls again this year - but i'm well over regulations thickness as it stands.
Does solar not have its own issues as regards payback? Even if its less, its not as attractive to me as it just works out that I wouldnt get as much benefit out of it. Have two (electric) showers - and couldnt justify changing this setup immediately. Otherwise, hot water useage is not as big a deal as central heating. From what I've read, photovoltaic will incrementally become more and more efficient over the next couple of years - so i feel its right to hold off for now.

feckoffcrow

Just came across this compact internal heat pump. Probably doesn't suit my particular circumstances (don't have the space) but would this not result in a more efficient system? ie. no energy expended on defrost to keep ice off.

Also, if used with secondary system - as in my case, an oil/rads system - as backup for when temperature drops to a level where it wouldn't be economical to use, will such use make this system viable??


One last question. Is anyone familiar with how the greener homes scheme works with regard to a system like this. I have read that air-water heat pump systems are covered but I'd imagine they probably wouldn't be covered in this instance where there are existing radiators in place...only if installing underfloor heating. Would that be right??

AC heating

Hi there
Installing a heat pump air-water in the Irish climatic conditions, one of the best solutions. Because the local temperature in winter never decrease lower than - 10 is not worth to consider the horizontal or vertical boreholes.From our past experience after some time, these boreholles may cool down to 4 degrees.Investment in such equipment shall be made in countries where temperatures drop and remain lower than - 10 in the winter months.The average outdoor temperature in the heating season in Ireland is 8 degrees.This is a stable heat source for air-water systems.Therefore, it is not unusual for the ground source heat pump has a greater heating costs than good air source. Considering that investment in ground source heat pump is twice as much in terms of return on this investment is not beneficial.
With a good system air-water you will not need a backup sytem, as the Performance of a heat pump installed on your house is always higher than the heat loss of the object at minimum possible temperatures . If you already have an oil boiler, there is no need to remove it when you install a heat pump.
Also i would not recommend a compact internal heat pump As these generally has lower COP than split systems that use the INVERT technology.
I do not know your house dimensions?but Just for example. <SNIP>...............
3100 square foot one-story house, standard radiators, a constant temperature of 23 degrees inside, the house heat loss 8kW / h, annual heating costs 650 euro.
This house was previously heated by oil boiler, with an annual heating costs 2300 euro.
Your question about greener home scheme.
Does not matter if you have radiators or underfloor heating,you'll probably be eligible for a grant if the product is on the list of registered products <SNIP>
and if the installer is on the list of registered installers

muffler

AC heating is permanently banned from this forum. Im going to send out a loud and clear message here and that is that company/business names will not be allowed and neither will people who attempt to use this forum for professional or business gain.

feckoffcrow

what air-water system would people recommend for integrating with existing rad system as detailed above?

I see a long list of contractors and systems on the sei's website - but i'm at a loss in determining whats what in terms of the actual systems themselves - thats before I even consider how reputable the company is.

NB - I don't want to draw anyone in - to defy mufflers warning above. I still badly need some direction - but please pm me system or company recommendations.

yop

OP - I would do more research on this tbh, I am not sure where you got the idea that gshp are not worthwhile? From my experience If GSHP are considering not worthwhile then ashps would be a definate stay away not unless its your ONLY option based on the experiences of people I know who have installed.

From our 5 year experiences with a GSHP we don't have any complaints, in saying that we have it running on underfloor heating and in a timber frame house with a lot of extra insulation.

Are you intending to run the system with rads or underfloor?

Have you considered a solar system or a condenser boiler if you are having doubts over ASHP or GSHP.
There is also the more expensive, but more efficent third option of the borehole heat pump.

Good luck

quentingargan

feckoffcrow wrote: »

what air-water system would people recommend for integrating with existing rad system as detailed above?

If you are using radiators, then any heat pump system will suffer reduced efficiency, unless you also change the radiators for fan assisted ones. The surface area of your rads has probably been designed around an oil system that runs water at a far higher temperature than a heat pump will. Of course, if you also improve the insulation of your house so that your radiators become over-sized for oil, you may have resolved this issue.

Also, be aware that when and if smart metering is introduced, there may be more than just day and night tariffs. Wholesale electricity prices can be extremely high between 5.00pm and 7.00pm, which is roughly the time you will need to be running this system. A heat pump with underfloor heating and themal mass can hopefully be switched off during this time, but not the system that you are developing.

If you have space for a very large buffer tank (2 tons or more) then you could run your heat pump off-peak and it may make sense.

Solar will make no useful contribution to space heating IMHO. Heat pumps are also not very good at getting water up to 60 degrees efficiently. So they are two separate issues. If your house is well enough insulated that your heating is only on for 6 months, then your hot water during the summer time is more expensive (because you either run the boilder JUST to heat the water, or you use electricity, both of which are expensive). If that is the case, and if you don't rely on electric showers, then solar will have a reasonable payback, particularly with the current grants.

feckoffcrow

yop wrote: »

OP - I would do more research on this tbh, I am not sure where you got the idea that gshp are not worthwhile?

Sorry for the sweeping statement - its difficult to tease out whats viable and whats not. I suppose if I was to put this more accurately, I guess I neither have space for gshp nor the willingness to part with the initial capital outlay for it - so just want to take it out of the equation in this instance.
I see an opportunity here to use air-water hp as it 'appears' as if the grant will cover it. There is a lot of negative stuff out there and it all boils down to the electricity usage - and i'm sure a lot of it is deserved. The conclusion I am coming to is that its possible to implement a solution that can be used as a secondary heating source ONLY when it is economical to run. I just need to figure out what system works best - and its at that point i'm lost. I'm also in Mayo - did your gshp contractor also do ashp? If your experience was good, maybe you could pm me the details?

yop wrote: »

Are you intending to run the system with rads or underfloor?

Rads - already have existing oil boiler/rads system in place.

yop wrote: »

Have you considered solar or a condenser boiler if you are having doubts over ASHP or GSHP.

Solar: I have 2x electric showers in place - and the usage pattern here is we simply don't use hot water otherwise during the summer (oil system providing hw during heating season) - so solar is not all that interesting to me right now - will probably bite at a later stage as it gets even more efficient/cost effective.
The oil boiler is not terribly inefficient - but it wouldn't be the highest efficiency boiler either (Firebird 70/90). However, its only 3 years old and on that basis, I can't justify replacing it just yet.

quentingargan wrote:

If you are using radiators, then any heat pump system will suffer reduced efficiency, unless you also change the radiators for fan assisted ones. The surface area of your rads has probably been designed around an oil system that runs water at a far higher temperature than a heat pump will.

These are my rads - pretty standard.I'm looking at getting some heat into the house at off peak times - but what I have to work out is that this happens without the electricity overhead being disproportionate to whatever heat output is achieved.

quentingargan wrote:

Of course, if you also improve the insulation of your house so that your radiators become over-sized for oil, you may have resolved this issue.

Looking at tackling this from all avenues - will be checking options as regards external insulation also - but IF both options are viable, I will do both.

quentingargan wrote:

Also, be aware that when and if smart metering is introduced, there may be more than just day and night tariffs. Wholesale electricity prices can be extremely high between 5.00pm and 7.00pm, which is roughly the time you will need to be running this system. A heat pump with underfloor heating and themal mass can hopefully be switched off during this time, but not the system that you are developing. If you have space for a very large buffer tank (2 tons or more) then you could run your heat pump off-peak and it may make sense.

Well, if initial capital costs are covered, theres little to lose. I am not dependent on the system. The idea is that I have the oil set to run at times that its not efficient to run ashp. If that means not using it between 5-7, so be it. Or if it means, not running it at a particular temp, thats fine - I revert to oil. However, the buffer tank idea sounds interesting. Is there anyone out there implementing this solution?

quentingargan wrote:

Solar will make no useful contribution to space heating IMHO.

Agreed. My interest lies in Space Heating right now.

yop

I PM'd you the link there for the heat pump supplier.

Ok, its space you are looking at then.

I suppose your best bet is definately to look at your insulation, walls pumped, ceiling space well insulated?
Have you double glazing installed?
That would be a start to stop the heat getting out.

GSHP wont work thats sound, so you are down to ASHP or the borehole which doesn't require much area but IS definately more expensive. Whats the difference in COP between the ASHP and the borehole I don't know off the top of my head.

Solar wont heat your space without the whole place been covered in panels, are their more efficent panels out there yet which could heat the space?

Your rads and a heat pump wont work too well I would think, the fan assisted are the recommended rads for the pump from what I understand.

You have a boiler in 3 years? If you will be changing to a heat pump its going to be taken out is it?

quentingargan

yop wrote: »

Solar wont heat your space without the whole place been covered in panels, are their more efficent panels out there yet which could heat the space?

Currently panels are up to 80% efficient. In December in Ireland we get an average of .47KwHrs of solar energy per day per square meter. Austria gets more than twice that amount in December. Even if panels were 150% efficient you can't get blood from a stone.

The whole concept of solar space heating evolved in countries like Austria where they get bright sunny cold winters. We don't get enough of that in Ireland where solar is only good for heating water in the summer time when the heating is (hopefully) switched off.

feckoffcrow

yop wrote: »

I PM'd you the link there for the heat pump supplier.

Thanks for that.

yop wrote: »

I suppose your best bet is definately to look at your insulation, walls pumped, ceiling space well insulated?

Absolutely - was built with cavity fill and attic is well insulated for sure.

yop wrote: »

Have you double glazing installed?

Yes - albeit far from good quality (have had to get some additional sealing strips for them already as big gaps with air streaming through!).

yop wrote: »

You have a boiler in 3 years? If you will be changing to a heat pump its going to be taken out is it?

No - the idea would be to run both. ASHP to be used when its economical to run - so outside of the peak esb tariff hours.
Where i'm stuck is how to decide between all the ashp systems listed on the sei website (theres hell of a lot of them). I'm sure some are more efficient than others, more reliable, etc.

yop

feckoffcrow wrote: »

Thanks for that.
Absolutely - was built with cavity fill and attic is well insulated for sure.
Yes - albeit far from good quality (have had to get some additional sealing strips for them already as big gaps with air streaming through!).
No - the idea would be to run both. ASHP to be used when its economical to run - so outside of the peak esb tariff hours.
Where i'm stuck is how to decide between all the ashp systems listed on the sei website (theres hell of a lot of them). I'm sure some are more efficient than others, more reliable, etc.

thats the crux of it in choosing.

What I did was I got references off the companies that I came down to and rang the people who got installed. Went to see the installs and chatted to the people.
In the end I went for a Direct Expansion system as it had a higher COP and the installer was local(ish) and I got 2 good references off him.