Ground source heat - how to decide if it's cost effective?

JennyP

We live in an area with no gas - moved in a few months ago.



Our house has an old oil boiler.



Our neighbours are also on oil but one neighbour just had a ground source heat pump put in. We have fields so enough land to do the same.



Our options are:

1. Keep existing boiler as it does work OK (neighbour is retired surveyor and friend who is an engineer both think this is a good option as they say oil boilers go on for a long time.

2. Replace existing boiler with more modern condensing one (could save 20% on oil costs apparently but that would take a lot of years to recoup!)

3. Go for ground source heat pump.



I have read quite a bit already including existing threads on mse. But it's hard to work out costs.



Still waiting on a quote but we reckon installation of about £20k at least. I read somewhere that with the money you get back on one if these, you could get £3000 a year so it might pay for itself in 7 years. But also read much smaller figures.



Also I read that you only find out what you'll get back after installation which then seems to make it a rather expensive gamble.



Our house is five bed but in reality we live in only a few rooms - our room and ensuite, two reception rooms and kitchen. The other rooms are storage so don't need to be roasting hot except when we gave guests.



Any thoughts? Especially personal experience?



We already have solar panels installed by the previous owner (and wonder if that makes us ineligible for the scheme anyway?)

FreeBear

Had a door knocker yesterday trying to flog air source heat pumps claiming they were a low cost way of getting hot water...

If you are on mains gas (which I am), heat pumps are not a cost effective alternative.

Depending on how the system is set up and run, for each 4Kw of heat out, some 3Kw of electricity is required according to most of the assessments I've read. A badly set up system can end up using 4Kw of electricity to produce 4Kw of hot water.

Ground and air source heat pumps are good for generating low temperature heating (typically, around 35°C) and work well with under floor heating. For hot water (i.e. 50°C and above), conventional boilers are much more effective.

If I was living somewhere off the gas grid, and had a functional oil fired heating system, I wouldn't bother with investing in GSHP - Unlikely to see any return on investment in my lifetime. What I would consider is adding a wood stove & back boiler IF the size and layout of the property would allow it.

lstar337

You could also divert some of your excess solar generation to an immersion heater for hot water in summer months.

lstar337

I also suggest posting you question in the Green and Ethical section as they are knowledgeable about all that kind of stuff.

lstar337

FreeBear wrote: »

Depending on how the system is set up and run, for each 4Kw of heat out, some 3Kw of electricity is required according to most of the assessments I've read. A badly set up system can end up using 4Kw of electricity to produce 4Kw of hot water.

That seems a little pessimistic. Our Air to Air systems regularly operate with a better COP than that, and my understanding is that ground source systems are more efficient than air source.

Furts

Before you do anything there should be a meticulous appraisal of your home in terms of insulation, ventilation and air tightness. If this all gets implemented it is likely to cost you little in relation to the £20K for GSH. You will then find you have little need for heating, and are likely to stick with oil.

An example is my home. For eight months of the year my solar panels could easily heat my water needs, and give spare for background heating in say April and October. I need some heating Nov-March but because of high insulation levels this heat is minimal. No way would I have GSH - there is no need for it and it would be a waste of money and an overkill.

ComicGeek

With a high efficiency model from a reputable manufacturer, with the correct design and installation, the efficiencies can be really good. However, trying to simply bolt on a heat pump to an existing heating installation which hasn't been designed for low temperature operation is just asking for trouble - anyone trying to sell you a heat pump without looking at the existing heating delivery system and building insulation is just a cowboy.

I don't think I've ever been able to demonstrate in more than 15 years that a ground source heat pump system is a good economic decision, even with the Govt's renewable heat incentive payments. For projects without mains gas, air source or oil boiler/air source hybrid systems have always been the most cost effective - but that's with appropriate heating systems being designed in at the same time anyway, not as a simple boiler replacement exercise.

Are your solar panels producing electricity or hot water? Depending on system size you would probably be able to produce your hot water using these for the whole summer, so you're missing out on valuable hours run for your heat pump system anyway.

Personally I would be looking at a quote for a hybrid oil boiler & air source heat pump (such as from Grant), and a quote for a new oil boiler. But I would live in the property for a year or so first just in case I wanted to do any alterations or new insulation etc that may affect the size of the new boiler. Forget about the ground source, it's a waste of money.

Baxter100

The RHI payments will be based upon the heating demand listed on the EPC. The only insulation requirements that you need to fulfill (if applicable) are cavity and loft insulation, so you are best off getting these completed and then getting the EPC done. At this point any subsequent insulation measures you do (such as floor/solid wall insulation) won't then impact the amount that you can claim from the RHI as a new EPC isn't required.

Baxter100

In fact given that you moved into your house a few months ago there should already be an EPC. Go to https://www.epcregister.com to have a look at the EPC heat demand figure on the final page to get a rough idea of what the payments could be.

Baxter100

Just as an aside, someone I know is in line to receive around £115,000 for their GSHP over the 7 years of the RHI.....

It is a big old house though.