Thermal Solar Power - worthwhile under the upcoming RHI scheme?

Afternoon,

Originally my future home project was to simply replace my 18 year old G rated boiler with a straight swap A rated boiler.

How ideas grow arms and legs! Then I convinced myself that what I wanted was a conversion of my plumbing system from open vent to sealed. Then I saw the price of unvented cylinders and thought "well it's an extra 200 - 300 quid for a twin coil cylinder. That'll make a solar retrofit in the future somewhat easier".

So now I'm in the position of evaluating the benefits of hot water solar. I'm looking at a complete Vaillant solution - boiler, cylinder and panels. At Plumbnation, there's a 3 solar panel system with evcuated tubes for £3000:
http://www.plumbnation.co.uk/site/vaillant-aurotherm-exclusive-solar-heating-system-vtk-tube-collector-package/
So with labour costs, I'm reckoning the total price will be around £4000.

I've heard such a system will probably provide 1500kWH. Which is around £100 a year saving off my LPG costs. So 40 years to pay back without subsidies. Not worth it in my view (even with LPG price increases).

Now I've heard of a new Renewable Heat Incentive that's likely to come out this June. Apparently solar thermal will pay around 18p/KwH. http://www.rhincentive.co.uk/eligible/levels/. Assuming this all turns out to be true, it makes solar thermal pay for itself after about 10 years.

So, my basic question. Should I go for that Twin Coil Cylinder, or is the RHI just a load of rhetorical Nonsense for now?
8.9kw solar.  12 panels ESE,  16 panels SSW.  JA solar 320watt smart panels.   Solar Edge 8KW HD wave inverter.  Located Aberdeenshire
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  • [Deleted User][Deleted User] Forumite
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    The installer needs to be MCS approved. We have a twin coil cylinder and solar panels plus a wood pellet stove but I am not holding my breath, yet. We will know more in june
  • CardewCardew Forumite
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    Without RHI solar RHI is a joke in money saving terms.

    Your '40 years to payback' (£100 a year saving - on a £4000 system) is too simplistic. £4,000 invested long term will earn £160 a year interest invested @ 4%.

    In any case whilst a large system with 3 evacuated tube panels might well produce 1,500kWh pa much of this will be in the summer and you might have difficulty using the hot water.

    RHI will change the equation drastically if solar thermal qualifies, but then you have to factor in the additional cost of a system fitted by MCS approved firms.
  • edited 12 February 2011 at 9:17PM
    frozen_wastesfrozen_wastes Forumite
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    edited 12 February 2011 at 9:17PM
    I think I'll just do the twin coil cylinder for now. It's £150 more expensive than a similar sized single coil cylinder. So it's no big deal if the RHI turns out to be a watered down affair.

    Personally I'd prefer to see lower kit prices for the solar hot water systems. The panels don't look too complicated from a materials or engineering point of view. I'd have thought the manufacturers would be able to figure out lower production costs for these units.
    8.9kw solar.  12 panels ESE,  16 panels SSW.  JA solar 320watt smart panels.   Solar Edge 8KW HD wave inverter.  Located Aberdeenshire
  • Ken68Ken68 Forumite
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    Surprised the Treasury have taken over.
  • frozen_wastesfrozen_wastes Forumite
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    The other consideration I haven't factored in is whether there's any evidence of how much my house value will increase relatively speaking. I've heard a suggestion that for every $ saved in utility bills annually, your house improves in value by $20. It sounds like a plausible formula,

    Applying this formula, I would be short of £2000 if I installed today, and sold my house tomorrow. There's also depreciation to consider, I reckon such a system would probably last 30 years before requiring replacement (less if these vacuum tubes are easily damaged by storm debris).

    So without RHI, the Vaillant tubes don't look like any kind of money saving deal. Solflex tubes are about 2/3 the price, but I have no idea as to their reputation. Solflex could just about be worthwhile without any subsidies.
    8.9kw solar.  12 panels ESE,  16 panels SSW.  JA solar 320watt smart panels.   Solar Edge 8KW HD wave inverter.  Located Aberdeenshire
  • Ken68Ken68 Forumite
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    Worth getting a quote now, Frozen,from a qualified plumber without the benefit of RHI, and then later on from an accredited trader.
  • CardewCardew Forumite
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    The other consideration I haven't factored in is whether there's any evidence of how much my house value will increase relatively speaking. I've heard a suggestion that for every $ saved in utility bills annually, your house improves in value by $20. It sounds like a plausible formula,

    Applying this formula, I would be short of £2000 if I installed today, and sold my house tomorrow. There's also depreciation to consider, I reckon such a system would probably last 30 years before requiring replacement (less if these vacuum tubes are easily damaged by storm debris).

    So without RHI, the Vaillant tubes don't look like any kind of money saving deal. Solflex tubes are about 2/3 the price, but I have no idea as to their reputation. Solflex could just about be worthwhile without any subsidies.

    You might save £100 a year with a large 3 evacuated panel system. - with LPG - not if you have gas

    However do you really think the panels and connections stuck on a roof will last 30 years without deterioration?

    What about the pump, electronics, valves and special to purpose HW tank?

    Also people tend to ignore the electricity consumed(at daytime rates) to run the pump and electronics. The Government commissioned report on eight solar thermal systems found the cost of this 'parasitic' energy to be quite high in relation to savings.
  • frozen_wastesfrozen_wastes Forumite
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    Yes, I think you're right. 30 years is optimistic for exposed plumbing under high thermal stresses.

    Time to lay solar thermal ideas to bed. I'll just stick with the boiler replacement and plumbing conversion.
    8.9kw solar.  12 panels ESE,  16 panels SSW.  JA solar 320watt smart panels.   Solar Edge 8KW HD wave inverter.  Located Aberdeenshire
  • [Deleted User][Deleted User] Forumite
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    Cardew wrote: »
    You might save £100 a year with a large 3 evacuated panel system. - with LPG - not if you have gas

    Also people tend to ignore the electricity consumed(at daytime rates) to run the pump and electronics. The Government commissioned report on eight solar thermal systems found the cost of this 'parasitic' energy to be quite high in relation to savings.

    I absolutely agree with that and when the solar pump comes on then my owl monitor jumps to 500 watts from a steady background of around 270 watts. In our case the PV system is providing enough energy to `pay` for the solar pump. The background cost of running the solar thermal system should not be overlooked
  • [Deleted User][Deleted User] Forumite
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    MoneySaving Newbie
    Yes, I think you're right. 30 years is optimistic for exposed plumbing under high thermal stresses.

    Time to lay solar thermal ideas to bed. I'll just stick with the boiler replacement and plumbing conversion.

    The solar system will need a bit of maintenance eg the antifreeze needs to be changed every 5 years and we already had one faulty collector sensor changed due to an installation mistake. The plumbing all looks quite complicated
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