UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

albyota

Edale wrote: »

Well looking at how mine is performing so far I have to agree it will be considerably cheaper to run than my previous old oil boiler and I am sure it will also be a lot cheaper than the most efficient new oil boiler available. The problem lies in the capital expense of the systems being so much higher which excludes many people from making the decision.

I would hope that, without any financial assistance until July that the thirty odd manufacturers would reduce their prices, after all, its their product they want people to purchase, on the other hand, people who have purchased hybrid cars like the Toyota Prius or Honda Jazz and spent between £17k and £23k will have done so to reduce their running costs....80mpg, no road tax etc...are they expecting to get government assistance for their running costs?

Oil and LPG are going to continue to rise, and over the next five years, unfortunately, Oil / LPG users are going to be spending a lot more, (58.9p/L, £618.56 inc Vat for 1000 litres oil tonight on boilerjuice) approx 10,000 kW/th @ 90% efficiency.

A correctly installed heat pump with an annual COP of 3.0 with the correct size radiators would provide 10,000 kwh of heat for approx £367 @ 0.11p/kwh.

£6k to £9k spent now on a heat pump can considerably reduce the annual running costs.

if your oil use is more.....

2000 litres oil = £1,200, Heat pump £740
3000 litres oil = £1,850, heat pump £1100

The EST heat pump trials carried out in 2008 only tested 29 ASHP's, there is currently over 12,000 units fitted in th UK now. we are only going to hear of the handful that have under performed, A disaster?, I think not!

peat

I would suggest that it is very unlikely that heat pumps will have a COP of 3 for the four to six months of the year when much of the north of Britain struggles to reach an average daily temperature of 7 degrees. And this is the period when most heat is required.

arty68

arty68 wrote: »

Hello,

Just thought I would share my running costs as I'm happpy with them . For the last 3 months my Electricity bill was £350 which I don't think is to bad considering we are an all electric house using the tumble dryer,washing machine and dishwasher daily.

so over all I'm very happy with my ASHP and this winter I was very glad I wasn't on oil anymore.

Just thought I would update ,

My bill for the last 3 months (end dec to now) was £ 337 which again I don't think is too bad considering the weather. It will be interesting to see how much it comes down in the summer.

paceinternet

"peat", it really is necessary for customers and suppliers to be clear on what they mean with COP and temperatures. Your post opens a can of worms as to what you mean by "average daily temperature of 7 degrees". Do you mean for example that the days min could be 0 and max could be 14 giving an average of 7. Even though 20 hours could have been below 7 and only 4 above 7. Or are you taking the hours into account?
Some customers may never want heating through the night and only in the morning and evening, and others may want 24 hrs a day ,and others want somewhere in between.
It can affect the average COP they achieve over a year.

Just as important is the system temperature they need for their type of room heating. Underfloor or radiators or fan coils etc.

Here are some figures for a low cost HP showing Air temp, water out temp and COP:
A -7 / W45 : 2.4
A-7 / W35 : 2.8
A7 / W45 : 3.5
A7 / W35 : 4.3

Probably the Brand leaders will do better than this, but it illustrates the point.

If the customer ran their system at 35 degC it would most likely achieve a COP of 3 or more for your 6 months when most heat is required.
At 45 degC, it could be close.
In spring and autumn, it could do better than 3 and you could get an annual figure of 3+.

Cardew

albyota wrote: »

A correctly installed heat pump with an annual COP of 3.0 with the correct size radiators would provide 10,000 kwh of heat for approx £367 @ 0.11p/kwh.


The EST heat pump trials carried out in 2008 only tested 29 ASHP's, there is currently over 12,000 units fitted in th UK now. we are only going to here of the handful that have under performed, A disaster?, I think not!

But they haven't tested 12,000 units!!!!

I agree that if a heat pump system did produce an annual average of 3.0 that would be acceptable.

However on the 29 ASHPs(from several manufacturers) that were monitored the results were way below 3.0. as low as 1.2.

It is no good saying 'correctly installed' when those 29 systems, with all the manufacturers involved in the year long trial, performed so badly. The conclusions of the EST were that they needed to find the reasons for the poor performance.

How would Joe Public know if the system had been installed correctly if the manufacturers and installers apparently don't know? You are hardly going to get an installer admit that they are clueless how to properly size and fit an ASHP, and yet it is blindingly obvious that is often the case.

We have a position where customers are expected to pay £9,000 for a system, with absolutely no guarantee of performance, - just take a gamble - and no real way of proving that the system is unsatisfactory; apparently sky high bills or unsatisfactory room temperatures don't qualify as proof.

Surely all the horror stories on this forum and elsewhere on the internet can't all be wrong!

P.S.
It is also pertinent to point out(again) that the, say, 10,000kWh you used as an example is far less effective than 10,000kWh produced by 'normal' electrical heating or gas CH.

Because of their low water temperatures, ASHPs have to run constantly during the day to maintain the house temperature. If you are out at work all day, much of that heat is wasted.

With gas CH you can set it to come on shortly before you need the heat - you just can't do that with an ASHP.

Cardew

[QUOTE=paceinternet;42286530Here are some figures for a low cost HP showing Air temp, water out temp and COP:
A -7 / W45 : 2.4
A-7 / W35 : 2.8
A7 / W45 : 3.5
A7 / W35 : 4.3

[/QUOTE]

Nobody disputes that the specification of the heat pumps themselves can be impressive, but they are like mpg figures from car manufacturers - not achievable in practice.

You have consider the overall system performance and that can be dragged down by, defrost cycles, hot water to cylinder, incorrect sizing/installation, supplemetary heaters etc.

harryhound

Cardew wrote: »

Because of their low water temperatures, ASHPs have to run constantly during the day to maintain the house temperature. If you are out at work all day, much of that heat is wasted.

Heat pumps should not be installed in houses unless the draughts are all blocked up and the "U" values of all 6 surfaces of the box are averaging less than 1. (IMHO)

The idea is that you never let the building get cold.
Passiv Haus standard homes have been built that don't really need any central heating at all(*); but I have had a rich client targeted by heat pump salesmen and he lives in an unimproved (as far as insulation goes) oak frame medieval hall house.

It was built to burn logs and that is what it now does!

(*) Well designed coated windows facing in a southerly direction have a "negative "U" value".

albyota

Cardew wrote: »

But they haven't tested 12,000 units!!!!

No they haven’t, but where is the evidence of all 12,000 complaints?

I agree that if a heat pump system did produce an annual average of 3.0 that would be acceptable.

However on the 29 ASHPs (from several manufacturers) that were monitored the results were way below 3.0. as low as 1.2.

Why does EST state that…..

The ‘mid-range’ of measured system efficiencies for
air source heat pumps was near 2.2 and the
highest figures were above 3.0. The sample of air
source heat pumps performed comparably with
other European studies

14 Manufacturers including

Baxi Group
Danfoss UK
Mitsubishi Electric
NIBE Energy Systems
Worcester Bosch

Surely all the horror stories on this forum and elsewhere on the internet can't all be wrong!

The people who tend to buy these systems are very clever people, they have researched the products to the nth degree, and pretty much know which product to buy, choosing the right installer is their hardest decision, they are parting with a fair lump of money, to reduce their ever rising fuel costs for oil or LPG, they have vetted the installer, sometimes recommended by others, and if after two of the coldest winters the UK has had, I’m sure we would have heard from all of those 12,000.

Why does EST state that…..

The field trial shows that heat pumps have
achieved reductions in heating bills for some
customers – especially those whose installations
are off the gas grid and are therefore replacing
heating fuels such as electricity, LPG and oil.

The householders in our field trial sample reported,
overall, good levels of satisfaction with both space
heating and hot water provision. There was no
significant difference between users’ satisfaction
with ground and air source systems.

Many householders said that they had difficulties
understanding the instructions for operating and
using their heat pump. This highlights a need for
clearer and simpler customer advice.


P.S.
It is also pertinent to point out(again) that the, say, 10,000kWh you used as an example is far less effective than 10,000kWh produced by 'normal' electrical heating or gas CH.

10,000kWh of heat is the same whichever way you slice it, oil, gas, electric, heat pump or a box of candles. What you have to pay to get it is very different!

Because of their low water temperatures, ASHPs have to run constantly during the day to maintain the house temperature. If you are out at work all day, much of that heat is wasted.

FACT. Heat pumps do not need to run all day at all. But they are much more efficient if they only have to raise the temperature a little from 18 to 21, therefore keeping a house at say 15 or 17 whilst you are out, doesn’t really matter if it is costing you much less to heat your house than any other type of fuel. If you run it like a conventional heating system, it will cost more to run.

With gas CH you can set it to come on shortly before you need the heat - you just can't do that with an ASHP.

FACT. Air source heat pumps should not even be considered if there is mains gas in the house.

P.S. How much do you spend a year on oil or LPG……..nuff said, you are lucky to be on mains gas, there are two million homes off the gas grid suffering the spiralling costs of oil and the tie-in contract rip-off LPG companies.

Cardew, I respect you, and in the main, agree with you, but you only seem to be pulling out the negatives, so I’ll provide the positives, I have had an ASHP since October 08 before they started the EST trial, with much lower bills than before with oil.

Please allow people who have had ASHP’s installed have their say, we all might just hear the real truth and learn from it.

Cardew

Albyota,
Likewise you contribute well reasoned posts, but on this I think we are at cross purposes.

The BBC report worded a little more starkly than the EST report.(which incidentally was only published in Sept 2010.) You have cherry picked some comments; well these are mine:

This report makes recommendations for consumers, installers, manufacturers and policy makers, and identifies areas that require additional investigation and research.


In a number of instances there was limited success in explaining the variation in measured performance. This finding may suggest that there are influences caused by factors that were not, or could not be, measured. An investigation of each site will be undertaken to help explain the large variation in performance, even in apparently similar installations.

Heat pump performance is sensitive to installation and commissioning practices.

Heat pump performance can vary considerably from one installation to another and customer behaviour is a variable that was shown to impact performance.

Many householders said that they had difficulties understanding the instructions for operating and using their heat pump. This highlights a need for clearer and simpler customer advice.

The impact of domestic hot water production on system performance is unclear. Heat pumps can be designed to provide domestic hot water at appropriate temperatures, but more investigation is needed to determine the factors which impact system efficiency.

Further study needs to be undertaken on an installation-by-installation basis, to record what has been done wrong (or well), what could be done better, and what exactly should be done in the future.

The worst-performing sites we monitored illustrate the need for customers to be vigilant when purchasing a heat pump, to be sure that they are buying the best system for their property and their lifestyle. Manufacturers and installers should also take care to ensure that heat pumps are specified and installed properly. The heat pump industry also needs to ensure that future installations are carried out in accordance with an agreed set of norms and standards. Installers need to be aware that they play an important role in educating customers on the best way to control their system

Be aware of the margin of error. If a heat pump is installed even slightly wrong, the outcome for the householder may be very wrong.

The EST are(understandably) committed to 'green' technology, however if anyone who has read as many technical reports as I have will recognise the above conclusions as little short of a disaster. Why else would they extend the trial to June 2011, but to see if matters can be improved? They certainly are not extending it to see if they can get performaces to deteriorate!!

Surely the point is that joe public hasn't a clue who is a good installer or not, and the manufacturers in that trial were not able to explain all the "differences in apparantly similiar installations". Also Joe Public buying these systems should not need to be 'very clever people'. Many, like members of my family, have difficulty in operating a simple CH system!!!

My point is that people should not be expected to pay £9,000 for an ASHP system and simply gamble that it might work well; and have no way of knowing if it is working well! or recourse if they are unhappy.

You may well be happy with your system(are you not in the trade?) and bills, but loads of people are not.

Clearly you shouldn't contemplate an ASHP if you have mains gas - but that is not the line heat pump salesmen take - and loads are fooled.

Incidentally 10,000kWh may be the same 'whichever way you slice it'. However how it is used is the factor that determines efficiency. Ideally that energy should only be used when it is needed. If you are out of the house you don't need to use any of that energy and it doesn't matter how low the temperature drops if you have a high output heating source to bring the house back up to temperature quickly. With an ASHP you don't have that that high output heating source, so you have to have it operating to keep the house up to a reasonable temperature; and the Law of Thermodynamics on heat transfer applies!!

albyota

Agree with all of the above, and I know DECC will favour and support this technology when the industry police (MCS) sort out the wheat from the chaff and removes the cowboys and helps to educate joe public.

Unfortunately the heating industry has, up to very recently been unregulated until CORGI now Gas Safe, the same with Part P for domestic Electrics, and was a haven for cowboys to operate, also the whole green bandwagon thing has attracted some 'Salesmen' without an ounce of knowledge, our existing housing stock needs to be double glazed, insulated and draughtproofed before installing ASHP's, Domestic heating systems can be quite complex systems, so to get it right, requires an experienced trained surveyor/heating engineer, with the acredditation from the manufacturer of the equipment being specified.

It would be great to hear from people who have an ASHP, and comment on this topic, good or bad.