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

[Deleted User]

Cardew wrote: »

Continuing the theme, most people on here are not considering the cost of installing an new CH system from scratch in a new house. They are considering retro-fitting an ASHP/GSHP or replacing LPG/Oil/Gas/Solid Fuel boiler.

If they go for replacing an oil boiler they already have a oil tank, radiators etc. With a combi, they don't need a HW tank, with an ASHP they do.

Just taking your point on 'hideous' oil running costs.

Oil is currently around 51p to 52p a litre, so approx 5.1p/kWh - a new boiler with a theoretical 90+% efficiency brings that to 5.5p/kWh so let us say 6p/kWh.

How does that compare with ASHP running costs - taking the cost of producing Hot Water? If John Pierpoint's research indicates an overall COP of 2.3 then we are not too far different from the 6p/kWh - say 5p/kWh; and COP = 2.3 is better than the EST trial average.

If the figure of COP1.6 to radiators is realistic then costs are higher than oil.

Then a point I keep repeating, and acknowledged by the EST, if you are out at work the ASHP is still producing(wasted) heat during the day as it is not capable of bringing a house quickly back up to temperature like oil/gas CH with water at 80+C through the radiators.

Well having had loads of properties with oil, lpg, mains gas and ASHP the ASHP has the cheapest running costs in what is oddly the least well insulated of all my houses. Funny old world

I also pay less on energy bills than many friends on GCH and vastly less than friends on oil even though they use it sparingly.

Not only that, having no gas means I'm not paying a second set of standing charges and annual servicing cocts etc. Also running costs are supplemented by the PV so unlike people on GCH I don't have to worry about how to use surplus energy.

An ASHP connected mainly to fancoils warms a house every bit as quick as mains gas so no wasted heat. Indeed the EcoDan is designed to be operated just like GCH in this config. I cant speak for oversized rads and UFH as these hold a large amount of water so I can understand that these are slower to react with the lower temps.

Anyway you raise many good points and have a great knowledge whereas I'm no expert just speak from personal experience No doubt there are many badly installed systems out there mainly ASHP varients, undersized, old non inverter models and some that were never intended to do domestic heating/dhw only.

If I had the time I'd explain some of my points better.

Cheers

lovesgshp

Pity that I cannot copy excel calculators (for GSHP ) on here from our research, but they are in Italian, even though you can alter energy costings.
I have Google translated a financial analysis explanation from the Word version, but not the full document.

• Estimate for competing traditional plant: gas wall boiler € 1000 + VAT, wall-hung boiler complete with accessories € 4500 + vat, mixing valve € 1000 + VAT; enameled steel storage tank ACS 2000 € (if GeoTherm steel, it is assumed the enamel as the steel would lead to a recovery almost immediately), total € 8500 + VAT
• LPG costs 0.65 Euro / l + VAT
• Power of LPG heater 11000 kcal / kg
• Hypothesis a 79241250 Kcal / annoanno heating
• Real yield of 90% LPG boiler
• Average cost of Euro 0,155 Kwh
• Annual increase in cost kwh 1% (historical data)
• Annual increase in cost of 4% methane (historical data)
• Time of observation 15 years
• The analysis is conducted including VAT at 10%
• Hypothesis 7 kW heat load

The analysis is divided into four different types of calculation:
1. Technical recovery time
2. Net present value technique
3. Technique of Internal Rate of Return



Technique of Time Recovery
The method tells us how old you reach a balance between the amounts of the cash flows of the two investment alternatives considered. As is evident from the graph (Fig. 1), the geothermal payback time compared to the second is 3 years. The weather is good, very content.

Cardew

jeepjunkie wrote: »

Hmm...

Comparing chalk and cheese then.

Hardly a fair comparison...

Why not?

It is exactly the same criteria they(not I) are using.

An ASHP connected mainly to fancoils warms a house every bit as quick as mains gas so no wasted heat.

What is the output of a mid-size Ecodan in cold weather? 7kW with water at 35C??

How can that possibly compare with a gas/oil boiler that can output 20kW to 25kW with water at 80C + in even the very coldest weather.

This is why every publication(and the EST) I have ever read states that an ASHP must be kept running almost constantly in cold weather and cannot be used like conventional gas and electricity CH.

This is the WHICH article - 'Air Source Heat Pumps explained'.

http://www.which.co.uk/energy/creating-an-energy-saving-home/guides/air-source-heat-pumps-explained/

some quotes

The EST says that a 'typical' air source heat pump could save you up to £330 (replacing electric heating) a year. But be aware that only some of the heat pumps the EST monitored in recent trials achieved reductions in heating bills.

It found wide-ranging variations in performance, with the biggest heating bill reductions for households off the gas grid. However, the trials found that, without the RHI, an ASHP could actually cost you more if you are currently using gas or heating oil to heat your home.

ASHP lose their efficiency when the external temperature falls below 5 degrees Celsius. So in cold weather, an additional source of heating may be required to supplement the ASHP.

lovesgshp

Cardew.
We have worked out here, that a GSHP takes approx 3-4 yrs to recover the investment against LPG. This rises to 7 years against mains gas. With ASHP cop being lower and operating temps more critical, then the above will rise, although the initial investment is lower.

John_Pierpoint

Cardew, do you know the date of publication of the "Which?" reports?

The government's commitment to the Renewable Heat Incentive seems to have been 6 months away for about two years. :mad:

Cardew

Geotherm wrote: »

Cardew.
We have worked out here, that a GSHP takes approx 3-4 yrs to recover the investment against LPG. This rises to 7 years against mains gas. With ASHP cop being lower and operating temps more critical, then the above will rise, although the initial investment is lower.

Anything you say about economics in Italy I will believe without question!!!!

Let us take UK though and do some 'back of a fag packet' economics.

The average consumption for heating and hot water is in the region of 16,500kWh. So let us work on that figure and calculate running costs for a modern oil or gas CH boiler at around 90% efficiency.

With oil that works out at around 5.5p/kWh and gas is around 3.5p/kWh. So annual running costs will be £907 for oil and £577 for gas.

Taking a lower efficiency boiler costs might be say £1,100 and £700 pa.

Consider an ASHP with a very high COP of 3.0 and electricity at a low 10p/kWh the cost will be £544.

Drop that to a more realistic COP of 2.3(still better than the EST trial average) and the cost is £717.

So in summary:

Gas will cost approx £577 or £700pa.

Oil will cost £907 or £1,100

An ASHP £544 or £717

As explained above, for many people who are out all day, the heat from the ASHP during the day is wasted.

Now someone with Oil CH can chose to have a new boiler or fit an ASHP. The difference in fitting the systems IMO is a minimum of £5,000.

£5000 invested in a long term BS account will fetch £184 after tax. Borrow that money or put in a long term ISA and you are talking a higher figure.

Now please pick apart my assumptions, which I think have been generous toward ASHPs;) and tell me how on earth an ASHP can pay ever pay back the investment.

Whilst a GSHP gives a slightly higher COP, in UK I have not heard of a retrofit sytem cost less than £20,000. Happy to have your figures on that.

Cardew

John_Pierpoint wrote: »

Cardew, do you know the date of publication of the "Which?" reports?

The government's commitment to the Renewable Heat Incentive seems to have been 6 months away for about two years. :mad:

This year I believe, They also give this indictment:

The study found that only 13% of all sites in the trial achieved a level of efficiency the EST considers to be a 'well-performing' system, with the rest scoring below this benchmark. Ground source heat pumps were found to be slightly
more efficient than air source heat pumps.

This is perhaps my biggest criticism of heat pumps in UK. The industry expects the public to pay £10,000 or even £20,000 for a heat pump with absolutely no guarantee of satisfactory performance, and no way of measuring that performance other than huge electricity bills if they have bought a lemon!!

I also think the attitude of Mario2013 speaks volumes. i.e. the systems were 'poorly selected'!

I don't know the criteria for selection, but it appears the industry(Mario) feel the 87% with unsatisfactory results should have been ignored.

lovesgshp

Cardew wrote: »

Anything you say about economics in Italy I will believe without question!!!!

Let us take UK though and do some 'back of a fag packet' economics.

The average consumption for heating and hot water is in the region of 16,500kWh. So let us work on that figure and calculate running costs for a modern oil or gas CH boiler at around 90% efficiency.

With oil that works out at around 5.5p/kWh and gas is around 3.5p/kWh. So annual running costs will be £907 for oil and £577 for gas.

Taking a lower efficiency boiler costs might be say £1,100 and £700 pa.

Consider an ASHP with a very high COP of 3.0 and electricity at a low 10p/kWh the cost will be £544.

Drop that to a more realistic COP of 2.3(still better than the EST trial average) and the cost is £717.

So in summary:

Gas will cost approx £577 or £700pa.

Oil will cost £907 or £1,100

An ASHP £544 or £717

As explained above, for many people who are out all day, the heat from the ASHP during the day is wasted.

Now someone with Oil CH can chose to have a new boiler or fit an ASHP. The difference in fitting the systems IMO is a minimum of £5,000.

£5000 invested in a long term BS account will fetch £184 after tax. Borrow that money or put in a long term ISA and you are talking a higher figure.

Now please pick apart my assumptions, which I think have been generous toward ASHPs;) and tell me how on earth an ASHP can pay ever pay back the investment.

Whilst a GSHP gives a slightly higher COP, in UK I have not heard of a retrofit sytem cost less than £20,000. Happy to have your figures on that.

OK Cardew.

Retrofit system for a client here from lpg to gshp.(240 sq mtr house) He was paying circa Euro 5000 just for his heating, this was for 2 gas tanks as they kept running out and access in winter was not possible for the lpg tanker.
The GSHP with a 200 ltr DHW tank, plus excavation work etc, came to below E20.000. He reckons he saves around E3-4000 per year. He also says that the heating is more stable than with gas. This is a point also with other installations, with existing radiators that we have installed.
He has gas backup if needed, but, apart from a ground loop pump failing, which was replaced within 36 hours after 2 years (5 year g'tee), the sytem has worked to the design spec.
p.s. This guy is over 80 years old and very glad he changed.

[Deleted User]

Cardew wrote: »

Why not?

It is exactly the same criteria they(not I) are using.



What is the output of a mid-size Ecodan in cold weather? 7kW with water at 35C??

How can that possibly compare with a gas/oil boiler that can output 20kW to 25kW with water at 80C + in even the very coldest weather.

This is why every publication(and the EST) I have ever read states that an ASHP must be kept running almost constantly in cold weather and cannot be used like conventional gas and electricity CH.

This is the WHICH article - 'Air Source Heat Pumps explained'.

http://www.which.co.uk/energy/creating-an-energy-saving-home/guides/air-source-heat-pumps-explained/

some quotes

You know the anoying thing... I would know what my COP is thanks to Mitsubishi wanting to monitor the system but had to say no because DECC/EST want to monitor it.

So far I have been arsed around by DECC/EST with regard to monitoring and RHI with yet another pointless/stupid email received from them last week. Should really change my email and let Mits monitor it...

To sum up I would not put to much faith in their figures but on the upside my COP must be really good.

PS In sub zero temps/severe weather the ASHP does 45C but can go up to 55C. As the fancoils are sized to rooms heat requirement it makes no diff it is 80C or 45C. It is the largest model btw.

Cheers

[Deleted User]

I'm not sure I can add much more but what bothers me is that each manufacturer has their own implementation of Air to Water heat pumps. Plus each property has its own requirements etc. None is this is really put across by the EST. It is far to general...

For example our EcoDan is a self contained unit which then pumps hot water inside to heat tanks which store the hot water and drive the fancoils and ufh.Simple controls like a GCH boiler coupled with weather compensation to be as efficient as possible.

Another system is a low temp Daikin which pumps hot refrigerant into the house which goes through a heat exchanger then onto tanks for hot water and UFH. Each room has a thermostat and can call for heat when required

Another is a Daikin high temp unit retrofitted to existing rads and pipework. New tank though.

Lastly an ASHP driving ufh downstairs and rads upstairs in a new build.

From knowing the owners with these systems it is pretty clear that it is not easy to generalise about ASHPs as each install is tailored to the house.

One may be using cheap rate overnight. I’ll let you guess. Others have fast stop start times. Some may run constantly in cold weather. All have different control systems, some simple others very complex. The owners all have different expectations and have different running costs but all have one thing in common...They all rate them very highly and are glad to see the back of oil and LPG.