Ground Source Heat Pump Costs

[paw1976]

Hi
I am renovating a 1960's bungalow into a 5 bed house and am considering a ground source heat pump (GSHP). The house will be fully insulated to modern building regs and we will probably never move house! We dont have the land for slinky's so it would be a borehole system. The cost of boreholes and GSHP = approx £15k. Whilst I understand it would eventually pay for itself and provide 'free' electricity I have been told that in winter the system is boosted with electricity and as it will only heat water to 40 degrees, electricity is constantly used to boost the water to 60-65 degrees. If this is the case, then are they any cheaper than gas?? Does anyone have any idea of how much electricity these pumps use and what the electricity costs associated with them are?

 

[Agile]

If you have mains gas then thats always the best solution in my view.

Its also far cheaper to fit an air to air heat pump if you must choose higher installation and running costs. They are not greener by the way.

All heat pump solutions need an under floor heat output to be effective anyway.

Tony

 

[paw1976]

We do have mains Gas and the whole house will have under floor heating.
Thanks for the reply.

 

[Keston]

don't bother with air source... with the humidity of the weather here it really wont be paying for itself for years and years (not in your lifetime)

Outside the UK air source heat pumps are extremely common due to the hot weather.

Stick with a simple boiler for all your needs. (personally I wouldn't even bother with solar either)

 

[timmel]

Any air source or ground source system will consume electricity all year round when the system is switched on. The reason these systems are appealing is because of their high Coefficient of Performenace (CoP), which can typically be around 3.0 (i.e. 300% efficient). That means 3 units of heat output requires 1 unit of electricity input. Let's say electricty costs 10p/kWh, that equates to 3.3p/kWh of heat output.

A typically gas system may be 90% efficient, using gas at around 3p/kWh, therefore costing exactly the same in fuel costs per unit of heat output.

Now I have conveniently chosen these fuel prices to illustrate that the running cost (in terms of fuel anyway) would be the same, but you can see that even if your electricity was a bit cheaper and your gas was a bit more, it would take quite a qhile to pay back your £15k.

You also need to consider that underfloor heating will cost more to install than radiators which I don't know if you ahve included in your £15k or not. A final thoght, think about fuel security and which way prices are going, which fuel do you expect to increase in price more, gas or electricty? (I don't know that answer to this question but thought I'd throw it out there as food for thought!).

If I were doing a project like yours, I would definitely take inspiration from our Scandinavian friends... use VERY good standards of insulation and airtightness to almost diminish the requirement for space heating. Then get a solar water heating system to take carre of your hot water demand.

 

[WDIK]

F.I.T. look it up

 

[Biggles..]

As an installer of ASHP and GSHP i would recoomend that you consider a gas boiler and put the other £10K towards the cost of heating your home for the next 10years. Never in your lifetime will the above products pay for themselves or in anyway cost you signifiacntly less to run than that of gas.

problems are at present(from a refridge point of view) that none of the uk units utilise the gases correctly,they chose the wrong gas and lack the correct amount of stages to get up to the temperatures required for spcae heating,let alone DHW requirements.Due to this the elecctric aux heaters will always run,most units then draw 45amps, electric bill becomes sky high.

From experience, no underfloor company will issue you the same guarentees as normal gas fired heating unless they can effectively have 45deg at the blender,some companies wont even do you a design without this.

The radiator side becomes a joke, having to oversize 20% to allow for the low temp,making the space for radiators required huge.

As for borehole or even slinky lay,at present during the past weather we've seen numerous frozen loops, not bad install by companies just the equipment is not good enough to deal with the cold.

COP is another issue,manufacturers currentl flaunt the loopholes when issuing the figures by altering what they rate depending on outside temp.BS states should be done at 5 deg giving a cop of about 3-4,some use higher outside temps givng higher COP.Recent outside temps of 0- -10 have seen COP's of less than 1(worse than gas).

Recent averages from customers surveyed have shown that on comparrison with gas there is absolutely no differenece.

Products to look at are Nebe for GSHP, or Daikin for ASHP however both are still lacking but are the better of a bad buch.

Would i recommend it,the truth is just this week a refridge firm we do work for, want to get into ASHP,with us doing the mechanical,unfortunately we've had to tell them we're not interested until they can prove the products to be of any reliability of proven gain as we'll be the ones that get the blame when the customer is no better off.

If your a raving green and feel having any renewable(solar,pv,wing,ASHP,GSHP,CHP) is like doing your bit then go ahead waste your money,dont expect a return from it or to be any better off financially.

Lee

 

[Happyplumber]

Out of all the green technologies available today the only one i would recommend is solar hot water,even this has to be set up correctly as well as cleverly to achieve the hot water side

One of the excellent technologies called gassaver,created by company called xenex which has now got help from Baxi and they are using it on their boiler range is a another product extracting heat from the flue gas

Alot of this greenwash technology being sold today is making money for the salesmen and the initial cost will never be realised in our lifetimes,but if it makes you feel good go for it

There are alot of different possibilities and with all new builds having to use minimum of 10% renewable technology we will have to fit this kit,but none of it has not been well thought out and too many sharks in there too

I do some work for a small developer who will build a minimum of twenty odd houses a year, all of these are using Ariston Solar hot water,twin coil cylinder and mall boiler with under floor heating work beautifully,and plenty of solar hot water

 

[Keston]

As stated in them extremely big and helpful posts it's really a no go area if your looking for a return.

Although you do notice the difference with solar even that is going 2 take years n years to do providing you don't have any breakdowns...

 

[Agile]

very sensible and realistic postings about the inabilities of heat pumps to make any advantage on costs when mains gas is available.

If oil or LPG is the only fuel source then ther can be some advantage but even so the sums need to be worked out very carefully.

It helps to have some idea of how electricity is made to better understand the economics. Gas or coal or oil is burnt to create steam to power a turbine to generate electricity. That process is only about 30% efficient.

It creates a situation where electricity is always going to be about 3-4 times as expensive as the gas.

That means that to produce 10 kW of heat you have to burn 11 kW of gas ( or oil ).

Equally a heat pump has to consume about 3-4 kW of electricity to poduce 10 kW of heat.

Dont get too hung up on these quoted COPs. The ones quoted are based on the best that can be obtained. Thats an air temperature of say 15° giving a heat output at say 45°.

When the source falls to 0°C the output could fall to 30° and the COP become far closer to 2 than 3 and thats just when the most heat output is required.

Few users bother to calculate their COPs and just assume its at the brochure figure 100% of the time.

Tony

 

[Biggles..]

sorry it all sounds a bit negative,but people should be aware of some of the pitfalls.

Problem with COP rating of the unit also comes back on the manufacturer, they quote all these figures that truely are designed to misslead you.How can a unit be 400%eff when due to the gas process all units regect a third of their own heat through the refridge handling side.

therfore a 15kw load requires a 20kw unit for rejection.
Beware manufacturers that tell you the unit is blah KW because they might not have calculated the rejection into that and your unit is undersized.

Due to the units being so small(uk wise) they have to alter the heating/dhw priority giving the units a firing sequence,40 minns/h heat......20mins/h hot water.If you connect direct to the units this will cause the aux heaters to kick because the unit cant cope with space heating when trying to do hot water and vice versa.

Best current solution for greatest eff is to connect heatpump to a buffer tank and allow to firing for 60mins/h direct to the tank and then take your drawoffs from this. The result of this is yet more space for already oversized lumps.

Lee

 

[Keston]

Best current solution for greatest eff is to connect heatpump to a buffer tank and allow to firing for 60mins/h direct to the tank and then take your drawoffs from this. The result of this is yet more space for already oversized lumps.

although I'm no expert, I do believe Keaton specify the use of a buffer tank with their heat pumps.

I have seen kestons 9kw range, the things are huge! But they can't be that bad as I know th MD of keston has just fitted 1 at his home... Then again he has money 2 burn....

 

[paw1976]

Thanks to everybody who has posted. I think I will install a gas boiler with UFH and put the money I save into the renovation!!

 

[Agile]

A satisfied customer who has seen the sense of what we have told him.

Its also nice that all the professionals have agreed to give him the correct advice without being tempted to advise him to fit something which is not the best for him.

Just to add for the record. There is no CO² advantage of using a heat pump in the UK for the reasons I have outlined in my previous posting.

But in other countries like France where 80% of their power comes from nuclear or Scandinavia where near 100% of their power comes from hydro then the CO² situation is completely different and an electric heat pump is very ecofriendly.

We dont have it in the UK, but if a manufacturer were to produce a gas powered heat pump then that would be very efficient indeed. That arises because the 70% waste heat at a power station is just disposed of with no benefit whereas in the home that waste heat can be used for hot water and heating as well so the efficieny reaches nearly 100% in energy utilisation.

Tony

 

[Corgigrouch]

Tony, Sanyo make a range of gas powered heat pumps, unfortunately they are a little large for the domestic market... the EcoG unit even generates up to 4 kW of electricity too... However they are air source.. http://uk.sanyo.com/Aircon/Products/Gas-driven-VRF/ECO-G-Power/