RHI Makes ASHP cheaper than Gas Boiler!

[crispy]

Hi there,

I've been  ; my Dad is doing a new annex and is fixed on heating it with an ASHP. But he is on mains gas, and my arguments that the ASHP is no better in CO2 emission terms and that he should steer clear of the more complex technology are falling on deaf ears, and the RHI is making it worse.

Here are my calcs:


                                       Heat     Fuel                                Net
            Per Unit   COP   kWh PA    kWh PA   CO2 PA   Fuel PA  RHI     Install   Cost PA
Mains Gas   3.5p       0.9   5000      5500     1020kg   £194     £0      £1000     £194
ASHP        12p        3.2   5000      1560     920kg    £187     £350    £3000     -£162


Despite the ASHP being around the same for the environment, and around the same in terms of running costs, the RHI is skewing the argument; essentially the ASHP is £350 cheaper PA, at an extra capital cost of £2000 - a pretty good financial return.

This just seems completely wrong to me. Why should the Govt subsidise an ASHP to this extent when it is no better than a cheaper alternative?

So, I have 2 questions. (1) Is the government likely to go back on this ridiculous subsidy, or at least exclude households on mains gas from it? and (2) what can I say to my Dad to steer him on the simpler, easier approach of simply having a little gas boiler?

Cheers!

[martin]

There is an election coming up, the result of which MAY alter everything (or may not)........ I'd agree that it's an utterly ludicrous scenario - this is what comes of people (and government) worshipping at the shrine of the Mackay and believing the sums he got wrong, and several of the potty conclusions he leapt to!
I'm hoping for a hung parliament, - by the neck!

ps, superannuated fridges don't arf clank - and then you can point out he'll need another form of heating to take over when it goes below 10 degrees C............

[Ivan]

I think a CoP of 3.2 is probably unrealistic for an ASHP in the UK.

Prof. MacKay certainly favours heatpumps, and I have had a discussion on the matter with him. He's working on CoP data supplied by manufacturers, but you're not going to see manufacturer's declared performance in a climate like the UK (cold and damp). If you're running them in Southern Europe, then yes, you could realistically expect to see something akin to manufacturers' data.

But, you're right, according to the RHI, you might as well open your windows and turn the heating up full blast. They've got a year to correct this, and it will be considerably toned down before it goes live.

[billi]

Hi the independent  test results for heatpumps ( i know of In Germany ) show figures between 2.2-2.6 Cop for ASHP

By the way what does COP stand for? Does it include losses in the system as well  and the defrosting of the heatexchanger ? Or is it a simple power input vs output number ?

Billi

[EccentricAnomaly]

By the way what does COP stand for?

Coefficient of performance.

Does it include losses in the system as well  and the defrosting of the heatexchanger ? Or is it a simple power input vs output number ?

Yes, losses in the system (the pump itself) should be included.  For defrosting, I think it should be included but I suspect it doesn't as they normally specify the input and output temperatures but not the humidity of the air which would be needed to evaluate the power needed.

[brackwell]

HI,

Perhaps your dad is right ( i know it seems they are always wrong )

You do not say whether your dad intends using it for heating or DHW or both.  If its the DHW then i believe this is very borderline but if only for heating then the Air to Air HP wins hands down.

This is because 1) The temp increase is limited to say 18C and this will ensure a higher and more realistic COP perhaps over 5.0 ( assuming 13C uplift )

                     2)  A heat pump can be fitted for circa £600  as a DIY job essentially.  Compare that to fitting a boiler !!

For the hot water you fit solar panels and i dont think anybody argues about their efficiency. These can be supported by a inline water heater which also serves as a insurance policy.  These are efficient because no start up losses,pumps,dead legs, heat losses etc...... !!

This set up is cheaper to install and cheaper to run.

PS I have just had a quote from BG for changing my G gas boiler + one new rad,Blanking off 2 and re connecting 1  of £3950 before grant.   If i saved half my gas bill thats a saving of £100 /yr - a pay back time of  39.5 yrs !!!  This makes all the renewables sound like a bargain !

Ken

[crispy]

Brackwell - you & dad might be right, which is why I was posting on the forum for more opinions

The current plan is to install UFH, and to feed that from *something*, probably either a gas boiler or an Air-to-water ASHP. The prices I quoted were only guesses for the installation of either, not including the UFH etc, and my guess is based on the cost of the unit itself + 25% for install. I've probably underestimated on both.

He hasn't thought about what to do for DHW if he has an ASHP yet, yes, Solar Thermal is great but will still need backup in winter.

Cheers, Crispy.

[martin]

go for gas (and solar) - the recent thread about some poor chap's experiences with a "Nibe" system should be enough to place firm doubts in his mind - http://www.navitron.org.uk/forum/index.php/topic,10131.0.html - I'd suggest any ashp will suffer the same problems  

[Ted]

Whether or not the RHI for an ASHP will pay you £350 a year is incalculable at the moment as the heating and DHW load of a building will be deemed and this figure will be based upon a methodology that even DECC haven't decided upon yet. They have quoted SAP and SBEM as possibilities but that is all they are at the moment.

RHI is all about helping the government meet their commitment of 15% of all energy from renewables by 2020 target - nothing more or less. Including heat pumps in the definition of  'renewable' when there is still CO2 in the grid mix is a little questionable at the least.

[dhaslam]

A COP of 2.0  is a more reasonable  average for an ASHP.   Using only night rate  electricity as well  makes the cost of heat about 4.5 cent per KWh.   The last time I bought oil it was   83 cents per litre  which works out at about  10.4 cent per kwh at 8 kwh per litre.  Even if it is necessary to use an immersion to boost the heat using night rate electricity it still costs less than oil.   It is possible to raise the COP to about  4.0 by raising the temperature of the input air.     The important part is to raise the input temperature above about 7C,  which is relatively easy,  but I want to raise the temperature a bit more.     

[KenB]

Crispy,

I suggest that your father talks to existing ASHP users to get their views first. 

Problems with icing up in damp weather has plagued early ASHP installations.  Having to resort to the immersion heater and waste electricity auto-defrosting the ASHP is not doing anything for the overall system efficiency.

As dhaslam states a cop of 2  changes the situation considerably.  COPs of 3

Remember where your electricity is coming from.  In the UK our generation mix includes 45% combined cycle gas turbine, operating at an overall gas to end user efficiency of about 42%.  This would mean that you would have to have a cop > 2.65 to exceed the efficiency of burning gas directly in a modern A rated condensing gas boiler.

If your father is late middle-aged or elderly, and is thinking of investing in a new heating system - I would strongly recommend not doing anything too radical.  Maintenance and servicing of ASHP may cause problems, especially if the original installer has ceased trading.   The resale value of the property might be affected if it has a non-conventional system installed.  Worst case is that £2k+ is spent on ASHP, and then at a later date you have to install a conventional boiler.

We are going through a turbulent transition in domestic energy.  RHI, FITs and carbon trading have caused ripples and distortions in an already complex market.  As Ted says, it is currently incalculable whether RHI will pay the return that your father is expecting. There are too many large organisations trying to make serious profits from energy, that there is likely to be little left for the average end user.

In an uncertain climate, it is difficult to predict how domestic energy bills will rise over the next few years. Just 5 years ago, March 2005, I was paying 1.55p per kilowatt for gas - according to an old bill.  It's now 3.24p/kWh - more than doubling in just 5 years.  Where will the price be in 2015 or 2020?  I should not like to speculate.   However it would be a simple matter to count the years for it to double again.

The price we pay for electricity is very closely tied to the gas price, in a relationship that will become ever more tightly bound as more and more power is generated from gas.  With the rapid depletion of the North Sea gas fields, we are importing an ever increasing percentage of gas.

I would leave ASHP well alone until things settle down a bit, it could be a very bad investment. As Martin says the recent forum post about poor performance from the Nibe system - and that was in an eco-house, where everything else should be working in your favour.

If you already have GCH, then a boiler upgrade would be the cheapest solution.  Don't go to British Gas - there are numerous self employed heating engineers who will put a new boiler in for half what BG charge. 



Ken

[marktime]

Just to echo what Brackwell and KenB have said re Britsh Gas, I had a quote from BG last year and it was exactly the same number (£3950) and a local independant was exactly 1/2!

PS I have just had a quote from BG for changing my G gas boiler + one new rad,Blanking off 2 and re connecting 1  of £3950 before grant.   If i saved half my gas bill thats a saving of £100 /yr - a pay back time of  39.5 yrs !!!  This makes all the renewables sound like a bargain !

MarkTime

[Mostie]

Ivan, manufacturers rate the heating capacity at +7deg outdoor air temp. Mitsubishi electric units have 2 ratings the uk output is for -1deg I think.

Of course the idea of a heat pump working below freezing will incur the wrath of Martin 

[martin]

I've no doubt some can "work" below freezing, but at what COP, and how well do they manage in our damp climate?
No point getting wrathful over physics, we're rather lumbered with it.......

[dhaslam]

The frost build up is more of problem  if the circulating  water is cold.  If the return temperature is 30C or more the  frost can be quickly cleared  and takes quite a while to build up again.  If the return water temperature  is cold then the output and COP is greatly reduced.