Living in Sweden, we as most of our neighbours, all I must add living in houses of up to ninety years old and none less than fifty, have installed what translates from Swedish as "mountain heating". Very similar in design to Matthew's, it provides copius heating at very reduced prices. In a climate far harsher than U.K., central heating is a continous from October through until April, (as I write I can see whispy snow flakes still falling!). Yet, since installation, our heating costs are roughly 30% of the equivalent household relying on electrically powered central heating, the source of which comes primarily from HEP in our area.
As a Brit I was skeptical at first although feel I must champion the cause as the financial rewards over the coming years, even for the more environmentally challenged, make this form of heat generation extremely attractive. Save money and the environment, I fear this sounds almost smug!

Stephen Martin, Strangnas, Sweden

I'm building a house in France and installing an air/water heat pump. With 78% of electricity supplied by atomic power stations; one cannot reduce ones carbon footprint much lower. And I drive a Toyota Yaris, rated the second most green car on the planet (from birth to ashes) after a Chrysler Jeep (would you believe).
Cost of energy consumption is rated to cost about half or less of a gas or electric heating system.
The drawback is that it is an expansive piece of equipment to install, almost double a standard central heating system and is, according to the supplier, not suitable (cost effecectively) for heating domestic water.

M. Butcher, Weston-super-Mare, England

Cold fusion is coming, in the meantime, try Llama wool beanies and socks.

Richard Grosvenor, Cheshire, England

A friend of mine has a stream passing through his garden - not enough flow to drive a generator. But could it be used to drive a heat pump?

Anthony Cutler, Malvern, Worcs/UK

How much is it all costing? Can it pay for itself over a reasonable period at today's fuel prices?

Richard Ehrman, Oxford,

reversing the domestic refrigerator theory is correct for the system,but the fundemental part of a a high performing refrigerator is the quality insulation around the freezer and sealing of the door preventing warm air getting in once the freezer is at temperature so the compressor works less or a smaller compressor is used. Same theory for Matthews house improve the insulation you cant lose.

Dave Tilley, Peterborough, cambs

Surely with global warming houses will need less heating anyway? I live in the Turks and Caicos Islands and no-one here has central heating - nature provides all the warmth we need

Joe Sobey, Providenciales, Turks and Caicos Islands

I live in NZ and air heat pumps are common hear, much cheaper to install than the UK, a 6kw out unit, COP 3.2 costs £1300 equivalent installed and we get almost instant cotrolable heat. We all need to heat our houses so we may as do as cheaply as possible. Using air the will not get the problems associated with soil cooling

Art Cattell, Auckland, New Zealand

1) Make sure you account for the energy expenditures for the equipment and digging...

2) Make sure you take into account the potential for gradual loss of efficiency as your heat sink cools down... yes, over a 30 year period you can cool the ground around your house... at least I've read that.

3) What Ottorino said... above.

4) Until we re-localize, reduce transportation drastically, and shrink our carbon input to a tiny percent of current output.... we are on a sinking planetary ship. Your heat pump is one small action, which may absolve you of personal responsibility for some carbon output, but unless we translate this into a policy for all people, it doesn't matter much.

5) Don't imagine that doing this while driving your car every day really helps much.

Thank you for describing it and making the effort!

Mike, Portland, Oregon

The trouble with heat pumps is that they typically work on a ratio closer to three times the energy required to drive the pump rather than the 4 stated by Mathew.
As the Electricity Mathew will use will almost certainly be derived from fossil fuels he will only get back the energy used by the power station to generate his electricity.
It is much greener and more cost effective to install a higher level of insulation, and wrap up warmer.
Ground Source Heat Pumps used in reverse to cool buildings in the summer and heat in the winter can provide enegy savings over traditional air conditioning systems and this helps to maintain the temperature of the ground; which is important in dry ground with little heat flow.
Within 30 years all the developed world will have to learn to live without the power we currently take for granted. If we use agroiculture to provide Ethanol for transport what do people eat?

Anthony Ash, Chester, UK

By the way, one thing more to consider aboutthe extra insulation I've seen praised here. While more insulation might cut down on your electrical bill, it also keeps air trapped in the house longer. Lots of fresh air can come in through the those uninsulated cracks around windows and doors as it adds up. If you seal those off, it gives the air more time to get stale and provide good conditions for indoor mold growth. That's one reason why mold growth and asthma has been such a big problem in the last years and much less heard of in the past. So we might exhange one problem for another. I read some of the oldest people in the world like to sleep with their windows open, even in winter, so maybe we should consider that as well.

sc, Atlanta, USA

I'm afraid that Matthew Parris may be in for a bit of a disappointment. Not that the system will not work, but it may work less well than he now thinks it will. The reason for me saying so is that although the explanation he gives for the workings of the heat pump principle is absolute correct, he has forgotten a rather important aspect of the system. The heat extracted from the ground will cool it . Hence the soil around the piping will cool. The idea now is that the large reservoir of heat locked in the surrounding earth will restore the balance. The speed with which this can occur is determined by the thermal conductivity of the earth and this will limit the qualtity of heat that can be extracted per second (or per day as you wish). Earth is a notoriously bad conductor for heat, hence the flow will be small. It means that a very large catchment area is required for heating even a modest house. I don't think his system is large enough for comfort.

Dr E.J. Zuiderwijk, Cambridge, UK

I am sure your explanation of how the system works is correct. However, it appears as though heat is passing from the cooler to the hotter. I wonder what Flanders and Swann would have made of the theory. They sang about the Laws of Thermo dynamics
"Heat is work and work is heat.
Heat wont pass from the cooler to the hotter,
You can try it if you want, but you far better notter."

Joe, Cape Town,

Cost, Matthew, cost.

Phil Heath, Llanfairpwllgwyngyll, Ynys Môn

The central difficulty with energy conservation for householders less talented than Mathew Parris is that the payback period is perhaps as long as a mortgage term while people move on average every seven years and do not recoup their investment. Separate long term loans attaching to the property rather than the incumbents would be self-financing and so mortgage companies would be neutral about income requirements. Who would provide the finance? Our banks would be thrilled to be seen for once in a good light.

Fred Keeling, Almunecar, Spain

Ah, and I was going to stay out of this one...

Here we go - the problem is that people are fundamentally cynical and shortsighted - there's been plenty of that here so far. Whether it be saying that these heat pumps aren't going to make much of a difference, or global warming is a fable, or "I'm not giving up my SUV," there's certainly plenty of highhorsing about.

Yes, we do ideally want a paradigm shift on a global industrial scale, but it's we, the people, that must drive to initiate it, because you can be sure as hell that businesses aren't going to start the shift because it won't be profitable for a long time. One heat pump may not do much, but can you imagine if all of Britain started using it? The same rubbish is being spouted here as there was during the new lightbulb regulations announcement.

Sure, global warming may not be what's warming us now, but it's scientifically certain that it can happen. Let's not waste the reprieve we've been given by trying to be a smartass.

Martin E, St Andrews, Scotland

"Our holiday cottage". Says it all really.

P Vincent, Manchester, England

I've just had it with "green energy". There is a plan to cover Shetland with 200 enormous wind turbines for electricity to the UK mainland, thus destroying half the island in the process. Why should we be the sacrificial llamas to the slaughter?

Roddy Nicolson, Shetland, UK

Is this not all about perspective? It is perfectly possible to go for a walk on a freezing cold winters day and be totally snug. Skiers can spend 8 hours a day in sub-zero temperatures and be perfectly comfortable. We have all got used to expecting our home to be heated to a balmy 21 degrees so we can wear Tshirts inside. Would it not be much much easier and far cheaper to wear latest technology, lightweight, thermal clothing indoors instead of installing all these costly fadish systems?

john smith, manchester, UK

Holiday cottage ,sugests periodic use usually in warmer
weather.These systems bring the building up to temperature over a period of days, and are only economic
if kept near that temperature constantly, and especialy
through the winter.
Most energy expense is incurred during the winter , so i'm
willing to bet that a conventional heating system would be
cheaper to run in this case.
These systems are extremely expensive to install and
heat exchangers expensive to replace.
Spend the money on insulation instead, then you really
would save money and the environment.

John, Tralee, Ireland

Why bother? World oil production peaked in 2005 and every major oil field is in decline. Source www.theoildrum.com

John, London,

What well meaning people wanting to jump on the 'caring' bandwagon don't realise is that they're taking a big gamble on the science of global warming.

The standard answer to this is that it doesn't do any harm to be safe. This is the same numbskull argument that is used by the Health & Safety Gestapo.

In truth, erring on the safe side, is still erring. The money spent on this error is money that could have been spend elsewhere: perhaps on technology that would have genuinely transformed somebody's life, a cancer sufferer, and HIV victim or the starving in Africa. Instead these Greens have chosen to spend their money making themselves look good and gamble their money in the hope of making an infinitessimal difference to something that is quite possibly not our fault anyway (that big hot thing in the sky , the sun, is the competing candidate for the cause of global warming). The cost of this showboating is slower human progress and more, rather than less, human suffering.

Scary, Windsor, Berks

I am from UK and live in Sweden. When one of our buildings burnt down we rebuilt (160 sq.meters ground area, over 1000 cu.meters of inner space over 3 floors)and included a heat exchanger with a 140 metre borehole. We also installed an 'air' heat exchanger for the house.
Per cubic metre heated on all these building results in an average 62% saving on electricity consumption compared with 5 years ago. In January 2003 electricity tripled in price here. It has now fallen to be about 40% higher than the pre-2003 price.
We use less electricity, have more heat and have cost savings that, on present price predictions, pay for the installation/equipment over a 6 year period maximum.
Plus we 'set it and forget it'. We also have high insulation standards.

Keith , Bengtsfors, Dalsland,Sweden

How much carbon has been expended into the atmosphere from digging trenches, carting mountains of earth, and manufacturing pipes, controls, pumps, etc. Will the heat moved from a to b ever redress this pollution before the whole lot needs maintenance and eventual digging up and replacing?
And no doubt the narrow country roads nearby will need some repair after the diggers, loaders, and suppliers, have returned to their bases.
Everyone is madly rushing around wasting even more of the earth's resources on this sort of putative carbon saving exercise, believing they are reducing global warming. If the Chinese take it up, global warming will accelerate at a rapidly increased rate. An enjoyable Easter article from Matthew Parris!

Terry Cload, Tunbridge Wells, Kent

Why bother? Global warming can never be resolved just by saving little bits of energy. We burn 80 million barrels of oil a day. Reducing that by a few percent does not solve the problem. Far better to spend our efforts lobbying for a real, oil industry scale, alternative to fossil fuels. One third of the world's land area is desert. Let's use this land to build solar power plants at a scale that will make a real difference.

Mike Ayres, Bodmin, Cornwall

As a chartered engineer, I've been through all this stuff, and Matthew may not be as green as he thinks he is. Heat pumps achieve 4 units of energy output for 1 unit in. If the trenches are dug in inappropriate soils, or the coils laid poorly that figure can be a low as 2.

If that unit is electricity from the grid, then another unit of energy is thrown away at the power station generating the electricity, which means at best you get 100% gain.

Ideally, get your house very, very, very well insulated (I halved my bills by good insulation), run the heat pump from electricity generated by the wind, and have stacks of thermal solar panels for the autumn / spring sun with a subterranean insulated water tank with at least 6 tonnes of water to act as an energy store.

FInally use a simple heat exchanger to warm incoming air from outside and replace drafts with fresh air vents you control. I've done most of this and my heting bill is now 5% of what is was before.

Ottorino, Wiltshire, UK

OK if you have the money to indulge. Sadly this kind of 'efficiency' is fast becoming the preserve of the better off and these projects will be a matter of 'keeping up with the jones' . I would be interested to see how long he thinks it will be before the investment pays off - I suspect many years.

s walker, canterbury, uk

Could we put one in the Artic. Refreeze the ice cap,cool the ocean and provide green elecricity?

david redwood, london,

yes, absolutely the right thing provided the economics are right. Much better that wind turbines and solar for the moment ( although someone must be working on an economical roof top box).
I have sufficient land to do this, and would like to- please provide more details on cost & installation. My only reserve is that Big Gvt. if it is serious about Gl. Wmg. is not gettting behind the small installers that sell this stuff. Any grants going?

chilly sceptic, aylesbury, bucks

Too much for morning reading, would try it again in the evening and hope that I do get it at that time. Tell me again how do things get warm from cold?

Gulfam Zahoor, Lahore, Pakistan

No one can beat the Law of Coservation of Energy. If energy is removed at a greater rate than it can be supplied by the sun, the ground temperature will be reduced and grass and crop growth will stop.

this has been found where people have installed such systems in their gardens. Put your faith in uranium and hydro power like Sweden, France and Switzerland

Paul , Northwich, england

I believe Buck House has had this for years. One little point. If the Earth is warming, should this not be reversed to cool the house?

Desmond taylor, Houston, USA Texas

We installed a pump which take in the air and distributes the heat to the water filled radiators in the house.
Investment cost was 63000 sek= £4500.
We have halved our energy costs.
This in Sweden where the climate is harder than in England.
In England it would be even more economical to install
this system.(Beats stealing the oil from Iraqis:))

Karl Dentolfte, krokom, sweden

I`m still trying to get my head around the pumping in and the pumping out.It all sounds a bit iffy to me.

vague, edinburgh,

I think you have been somewhat patronising of your readers’ intelligence. You could have usefully provided a simple relative costing and said something about how the heat exchange compares with or differs from solar heating.

Henry Percy, London, UK

Sorry Matthew, a dreadfully patronising piece. Perhaps you should remember that a lot of your readers still live in a two up, two down, in inner city 'wherever' and will never have the opportunity to own a second home let alone indulgently spend the National debt on making it ecologically friendly.

judy, Liverpool, england

If the use of these 'heat pump' systems spreads, all taking heat from the earth, might there not be a danger of global cooling?

RobertW, Gerrards Cross, Bucks

I suppose the saddest part of this tale is your desciption of it as a "Holiday Cottage". I am sure the dozens of young , hardworking families who can't afford one home in the area they work, let alone two, look on enviously at you and your abused chequebook.
"Let them eat cake."! or would "Lodsa money" be more appropriate.

Van de Merve, Somerest,

Mathew it would be interesting to know to what extent you should be thanking the size of your cheque book for helping to heat your house.
If the true total cost of planning applications, amortisation of the installation cost, maintenance costs and runnning costs are correctly accounted.
During WW2 the Swiss, in isolation, developed a lot of expertise in reverse heat pump technology, as well as in low flow and low head hydro power generation, so that today they are less than 10% dependent on fossil fuels for electricity generation and there is plenty of expertise available in this field. It is encouraging to know that, 50 years further on, in England people are beginning to discuss it!
A word of warning. It is probably impossible for a family to depend on reverse hear pumps for all their heating and hot water, it will only supply a steady base load which will need augmenting with some other form of heat source, probably an oil fired boiler, the cost of which needs to be added in.

j.kelleway, bern, switzerland

Matthew, you do well what journalism is for, to inform and educate under the guise of entertainment. I hope you receive lots of invites to spice up tired Physics lessons with similar explanations of less understood technology, free of the tiresome quantitative stuff like Joules and coefficients.

Have you thought of adding a few Yak to your flock of ‘wooly sort of fleecy hairy goats, with indolent expressions and undulating throats’?

I’m told that when it’s ‘well rancid,’ the butter is good with tea (as an alternative to milk) and with muesli instead of yoghurt. It might even be a key to the longevity of some mountain folk. Research needed.

Look at using LED lighting on a low voltage solar generated circuit. A light emitting diode uses a tenth of the power of a low-energy bulb for equivalent light output, and at more than 100,000 hours mtbf should last and last.

dr venables preller, Warminster, UK

I am afraid this is article may be tinged with the "eco-illiteracy" that we are suffering from at the moment. If anyone is really interested in reducing carbon emissions they should look at their overall life style. I assume this is a holiday home and the fuel used driving up and down to it would easily exceed the "saving". If as a society we are serious about enery saving (and I am convinced we are not) we would look at the carbon impact of all we do. While we still fly our vegetables in from Africa and truck millions of gallons of bottles water around the country then we are just playing at it.

Adrian, COLCHESTER, ESSEX

Beware of the wind generator. A domestic version is not expected to last long enough to recoup the financial cost of installing it, never mind the carbon cost of its manufacture.

P Robbins, Cornwall,

As you pump heat from the ground it cools the ground. The outside gets colder. Perhaps this will affect tree growth? Retard the onset of spring just in your garden?

michael denton, lincoln, UK

. It is very efficient at heating, but it's not the case that no extra heat is generated. Extra heat is generated by the pump moving the fluid around. It has to be thus otherwise you'd violate the second law of thermodynamics.

John Small, Faversham, UK

Wish brave Matthew the best of luck. But I am not entirely certain that the idea is efficient in winter. Somehow, it is similar to collecting rain water: The butt is always empty in hot summer. Probably it would work better in a farm so that covered, half-filled trenches can be used as giant composting bins and generate that crucial extra heat.

H.Jameel, Camberley, Surrey

Two (probably naive) questions:

1. How applicable is this technology in countries, or seasons, where the aim is to keep cool rather than to keep warm?
2. Is this not another case of a technology which is a luxury option, only available to the rich?

Steven Patten, Doha, Qatar

Hi Matthew,
I've been looking at heat pumps too, would just draw your attention to http://www.kensaengineering.com/pdf/222.pdf, which points out the heat of the ground is not inexhaustible: it needs to be refreshed by summer sun or rainfall. It isn't the disruption that makes it more appropriate for new build: it is the fact that new build properties are well insulated. My leaky old cottage, it seems, is not. Though it may well be suitable for your requirements, heat pumps would also need to use a lot of power to produce the hot water required, year-round, for a family of four.

Jack Barker, Marlborough, Wilts

Adam Beswick asks about the amount of electricity used to power the pump and its relation to the energy gained by the heat pump. In a typical ground source heat pump, the ratio is more than 3 to 1 - three times more energy is captured than is used by the pump.

Chris Goodall, author, 'How to Live a Low-carbon Life'.

Chris Goodall, Oxford, UK

I am interested to know if the energy used to power the pump and compressor equals the energy that would be employed heating the water by more conventional means. It seems we may not quite have the full picture here.

Adam Beswick, Brisbane, australia

I so enjoyed your article about your heat pump adventure. Pls keep us informed as to how it all works out. I find your news to be quite refreshing compared to what we are offered on a daily basis.

Jane Eichstadt, Rockport, USA Texas

Will the amount of energy you save, Mr Parris, equal that used to dig two 100m trenches, transport 200 tonnes of sand, and manufacture the considerable quantity of equipment your heating system seems to require?

John Vincent, Christchurch,

What a fantastic idea :)

Karen Sampson, Adelaide, Australia

Costs and recovery Matthew. Or is this just for the "fortunate few"?

Bruce, UK, Malvern, UK