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Solar water heating

(19 Posts)
FurbysMakeSexNoises Sat 24-Oct-15 16:39:34

We've been suggested to get one of these by our plumber who is doing a massive bathroom job for us. His main priority is sorting out our hot water, we currently have an oil boiler. We are in the countryside and would consider a solar panel for heating the water for the boiler.

Has anyone any experience of this - pros and cons? Also where best to get advice on placement- does it have to be facing exactly south to get the best outcome? TIA

specialsubject Sat 24-Oct-15 17:27:56

no, it is far more complex than that. There are calcuations concerning latitude, shading, roof angle etc.

not a totally daft idea, especially with future energy issues; regard it as energy resilience rather than a cheap solution or a money maker.

like anything else; get quotes and do NOT let any of the 'free panel' lot near your roof.

notapizzaeater Sat 24-Oct-15 17:36:32

We've got solar panels and an "immersun". If we ever generate more electric than we use (most days at some pint) it diverts the unused electric to heat the water. We had it all installed last October and since then have never switched the water on.

yeOldeTrout Sat 24-Oct-15 18:00:40

You need to use a lot of hot water to make it economical.

whiteagle Sat 24-Oct-15 18:04:02

I looked into it and the high install cost make the payback years. Ruled it out in the end as we don't have the upfront cash for long term potential gains atm.

FurbysMakeSexNoises Sat 24-Oct-15 22:54:24

Thanks for all your thoughts so far. We would like to be less reliant on oil as prices are very likely to go up. So we wouldn't be doing it for getting it paid off quickly or the financial so much.

Can you use it for underfloor heating?

PausingFlatly Sat 24-Oct-15 23:08:30

Two ways of doing this.

1) Photovoltaic (PV) cells where you generate electricity and dump excess generation into the hot water tank, like notapizzaeater.

2) Solar thermal, where you directly heat liquid on the roof and pump the hot liquid into a heat exchanger to heat the hot water.

I have the latter and it's pretty good. Will work through a layer of snow on a sunny winter's day.

Obviously both types need a secondary heat source for overcast days, but you can get an integrated system. The latter should be much cheaper than a big PV system, but horses for courses.

PigletJohn Sun 25-Oct-15 07:14:05

If you are talking about a hot water panel, have a look at what you spend on water heating in the summer.

For example my gas in summer costs about 25 pence a day.

A hot water panel might save half that (there is much less solar energy in winter).

It might take me a hundred years or so to recover the cost of a hot water panel and special cylinder.

PausingFlatly Sun 25-Oct-15 10:02:21

An average solar hot water system generates about 55% of your hot water over the year (up to 90% during summer months).

Obviously a family will get better value out of it than someone living alone.

On hot water days, we use the solar hot water for additional jobs like laundry, preheating kettle water, etc, so we get a net saving on the electric as well. But we deliberately designed the system with a very small run off, etc, to make this worth while.

FurbysMakeSexNoises Sun 25-Oct-15 17:19:27

Actually thinking about it the only costs which would go down is the electric for the immersion heater presumably? And some reduction in oil use over summer from the boiler?

Where's best to get quotes from to price it up in order to decide? What do Which? advise does anyone know?

lighteningirl Sun 25-Oct-15 18:01:41

We have solar panels and an optimiser which channels excess solar energy to the immersion it works really well and bills have dropped dramatically.

JellyTipisthebest Sun 25-Oct-15 20:25:38

Not sure if its available in the uk but (but I think it must be as it says its made there) Thermodynamic box is what we are thinking about. Its even heats up at night when its cold. Might be worth looking into

PigletJohn Mon 26-Oct-15 11:42:30

don't know what that is.

FurbysMakeSexNoises Mon 26-Oct-15 22:28:15

So looking like costs are 3-5k per panel and get Max £125/yr savings and from January the RHI drops so can't see how it's financially sensible to do it even if it feels like a nice idea?

PigletJohn Mon 26-Oct-15 22:56:29

is that for a hot-water panel?

FurbysMakeSexNoises Wed 28-Oct-15 11:28:11

Yes I believe so from Which etc unless you have other info?

PigletJohn Wed 28-Oct-15 12:28:22


I remember seeing some tests of solar hot water, where the best payback (because cost was so low) was from DIY jobs using old radiators and old garden hosepipe. The principle is fine but if the installation is expensive it's not economic. My hot water is heated by the gas boiler, which is very cheap, and in a previous home the cylinder was heated by the multifuel stove in winter. If I had nothing but an electric immersion heater, at three times the cost, it might be different.

PausingFlatly Wed 28-Oct-15 12:49:09

£5K sounds expensive to me. I think £5K is what we paid a few years ago for a hot water panel + custom scaffolding for our awkward roof + new boiler + general renovations to the house.

We did it to be less reliant on fossil fuels, rather than purely for financial payback, although I think I calculated it will payback. Though for us it's hard to see which savings came from the panel and which from an efficient new boiler, plus number of people in the house has changed.

TalkinPease Wed 28-Oct-15 13:51:44

I have solar thermal and I LOVE it.

I was having the whole plumbing system revamped anyway so the incremental costs were
- extra coli in the tank = £200
- solar panel itself = £500
- solar regulator kit and pre expansion tank = £400
- specialist fitters = £400

it is 7 years old

My boiler is switched off from April to October - the panel produces 240 litres of water at up to 65 degrees every couple of days
so showers and washing for 4

In winter it pre heats the water - at this instant the panel is running at 53.9 degrees Centigrade

My gas bills are lower than before the building work, even though the house is twice as big

And the airing cupboard where the tank sits is the best place to store towels and bedding and swimming kit smile

If you are changing your boiler and tank anyway, the incremental cost is definitely worth it

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