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

albyota

Incidentally, the most important factor in changing from a conventional heating system to an ASHP is the emitters/radiators, and calculations made to upgrade/size them correctly, i.e for the lowest water temperatures 35 to 45 for rads, and the outdoor unit sized to cope so that in the minus 17 temps we had in Nov/Dec last, the defrost cycles do not affect the performance. All very well in hindsight, the UK has not experienced these extreme conditions for a long time, a typical heating engineer would only ever use minus 1 or 2 external with 21 degrees internal as per CIBSE, BRE, and not needed to worry about air moisture content. So the industry should have learnt this lesson now.

Cardew

albyota wrote: »

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

Just one comment on the above.

The big problem is that it is very difficult to quantify how well or badly an ASHP is performing.

That is why it was so interesting to have the EST report that gave verified results rather than the subjective, "I spent £x last year and this year spent £y"

Edale

Well my Ecodan seems to be working well, the house is certainly as warm as with the previous oil boiler and we have certainly had one frost in the 2 weeks since it was installed and the house was warm. Total electricity consumption has been 219kwh in the first week and 218kwh this last week (including washing, tumble drier, cooking etc). For the 8 months prior to having it fitted we used an average of 112kwh electricity and 60 litres of oil per week (during winter we were using 90-100 litres per week). At current prices of 60p per litre of oil and 8.3p per KWH of electricity, I cannot see how I won't save a lot of money.

However I think in the absence of the Renewable Heat Incentive the decision to install the ASHP against a new efficient oil boiler is much more marginal financially, when you consider the higher cost of the ASHP.

albyota

Cardew wrote: »

Just one comment on the above.

The big problem is that it is very difficult to quantify how well or badly an ASHP is performing.

That is why it was so interesting to have the EST report that gave verified results rather than the subjective, "I spent £x last year and this year spent £y"

True, it is the only technology to undergo such tests, people seem to accept advice by the Energy Saving Trust that....

" Boilers account for around 60% of the carbon dioxide emissions in a gas heated home. By replacing an old G-rated boiler with a new high efficiency condensing boiler and improving your heating controls, you will significantly cut your home's carbon dioxide emissions - saving as much as £225 a year."

In reality this is not always the case, for the same reason of differing temperatures (longer winters) from one year to the next. You would agree, that until someone gets their fuel bill SHOCK, that is when they actually start reading their meters.

albyota

Edale wrote: »

Well my Ecodan seems to be working well, the house is certainly as warm as with the previous oil boiler and we have certainly had one frost in the 2 weeks since it was installed and the house was warm. Total electricity consumption has been 219kwh in the first week and 218kwh this last week (including washing, tumble drier, cooking etc). For the 8 months prior to having it fitted we used an average of 112kwh electricity and 60 litres of oil per week (during winter we were using 90-100 litres per week). At current prices of 60p per litre of oil and 8.3p per KWH of electricity, I cannot see how I won't save a lot of money.

However I think in the absence of the Renewable Heat Incentive the decision to install the ASHP against a new efficient oil boiler is much more marginal financially, when you consider the higher cost of the ASHP.

Hi Edale, your averaging 31 units a day (whole house) around 12 units for the heat pump (99 pence), when external temps are quite mild 2 degrees to 10 degrees, in the depths of winter minus 7 and below, you can expect to be up around 90 or 100 units a day or more (£7.50 - £9.00) so if you had 6 months of minus 7 everyday (icelandic ash cloud that blots out the sun) it would cost £1,620.
kinda puts it in to perspective....

Cardew

albyota wrote: »

True, it is the only technology to undergo such tests, people seem to accept advice by the Energy Saving Trust that....

" Boilers account for around 60% of the carbon dioxide emissions in a gas heated home. By replacing an old G-rated boiler with a new high efficiency condensing boiler and improving your heating controls, you will significantly cut your home's carbon dioxide emissions - saving as much as £225 a year."

In reality this is not always the case, for the same reason of differing temperatures (longer winters) from one year to the next. You would agree, that until someone gets their fuel bill SHOCK, that is when they actually start reading their meters.

Indeed, having a G-rated boiler, I would like to see a similar 'field trial' of modern condensing gas/oil boilers.

I have read plenty of reports from heating engineers who advance the view that the claimed 90+% efficiency of these boilers is simply not achieved in practice.

However again evidence is usually of the "I used £x last year - now it is £y"

Also people having spent £thousands on a new boiler are often reluctant to admit that it doesn't seem justified by savings?(could also apply to ASHPs?;))

albyota

one point I'd like to make though, people are only ever concerned with the money side, so when a comparison is made of "I used £x last year....£y this year", for oil and LPG users it's, "next year I am at the mercy of the unregulated fuel suppliers cartel and cannot budget for these increases".

harryhound

Cardew wrote: »

Albyota,


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!!

One of the biggest factors is the people in the home.
A poorly insulated home, because the walls "feel" cold needs to be run at a higher internal temperature in the winter than in the summer.
People like a point source of heat to warm their cold bits.
People turn up the heating when they have got cold (say outside)
People open windows to cool off rather than remove cloathing.
People want the hottest home and radiators in the coldest weather.
People want to zone their home, especially the bedrooms.
People think they are going to suffer some sort of illness sleeping with the window shut.
People dry clothing indoors, then open windows etc. to get rid of the condensation.
People live in houses with insufficient thermal mass (and insulation) to smooth out the day time gains against the night time drop in temperature.

Unfortunately a heat pump with its falling performance as the external temperature drops cannot cope very well with any of these conditions, when it is retrofitted in to a UK house and heating radiators.
Sure you can turn on its supplementary heating that in Scandinavia might well use hydro electricity, but if you do that in the UK -> £££££.

lovesgshp

To Harryhound.

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.
Most passiv haus homes usually have heating systems in place. In the search for them in the Uk the 7 seem to have mainly gas condensing boilers. In Europe many have heatpumps.
http://www.passivhausprojekte.de/projekte.php?search=2

Unfortunately a heat pump with its falling performance as the external temperature drops cannot cope very well with any of these conditions, when it is retrofitted in to a UK house and heating radiators.

Most heat pumps drop return temps by 0.1C as external air temp increases on a scale and then increase the same on decreased external temp. Internal temperature sensor can override the influence, as can changing heat curves. In many cases, you can include a buffer tank to better stabilise the range for radiator systems. We have many retrofit systems here in Italy working on rads and our insulation levels are a lot lower.

harryhound

Yes I'm sure that by turning on the supplementary heater (immersion heater) in the depth of winter the home can be kept warm BUT what COP is being achieved over all?

Were the poor results, the Energy Saving Trust reports here in the UK, by the British representatives of the heat pump manufacturers, caused because all our competent engineers have become bankers?

It is a shame the EST has not named the guilty parties.

There is also this effect:

Jeavon’s paradox (1865):

"If the quantity of coal used in a blast-furnace, for instance, be diminished in comparison with the yield, the profits of the trade will increase, new capital will be attracted, the price of pig-iron will fall, but the demand for it increase; and eventually the greater number of furnaces will more than make up for the diminished consumption of each."

The effects in use of these energy saving measures are coming out as 30% less that logically they should – this is in part the effect of poor workmanship; but mainly the users’ response. Particularly in social housing the attitude tends to be “Wonderful, we can now afford to live like rich people, not needing to shiver in our bedrooms” etc. The result being that the indoor temperature in January is HIGHER than in July and the occupants are lounging about in front of the plasma TV in a “T” shirt; then they moan that the utility bills have gone up. [Not new: British Gas observed this effect in the 1970’s where half the savings created by insulation were utilised as higher levels of comfort]

Talking of 1970's experience - The first oil shock caused consternation in Austria - no sign of natural gas or North Sea oil coming to the rescue there. So the Austrians went for Heat Pumps in a big way.
It was not a success and many of the installations were junked long before their engineering mean time to failure of 20 odd years.

I notice that part L1B of the building regulations now expects an installation to offer proper training and commissioning of the system - theoretically the days of "I've left the manual on the kitchen table luv" have now been replaced with "Here is the system log that you will need to keep up to date if you want to claim the RHI and if you have any problems we have a 24/7 help line".


As the old saying goes:
"You can lead a user to a manual but you cannot make them think"