Solar Power-is it worth it?

bobmedley

But surely it would be better just to swap your water heating to E7 at around 4/5p per kw? The interest alone on the £2.5k would pay for your hot water on the figures you have punted. The bottom line is that there is no real need to use expensive LPG to heat your water at 7p per kw.

I don't think anybody doubts the virtues of solar/biomass etc, it's just the payback periods are nonsensical which leads to the conclusion that;

a) The new technology prices are too high

or

b) Current energy prices are too low

Wonder which it is?;)

Cardew

moo2moo wrote: »

Accepting Cardews worst case figures that this will save me £120 per year then the solar install (£2575) will pay for itself in 23 years assuming I buy mains gas at 4p / KWh. However since I buy the rather more extortinately priced LPG from Flogas which is currently at the 50p/l mark assuming I reduce my LPG usage by 400l per year (just a random figure.. although Driller_Killer used this amount in 2 months) saving £200 then this quickly reduces to 13 years. Lower usage, quicker payback. Using Driller_Killers figures (flawed though they may be by an elderly boiler) as an example even if my solar system was only operational for 4 months of the year (May-August) then the savings would be £400 per year or payback in 6.5 years. On the otherhand if Flogas double the cost of LPG again over the next 2 years (as they have since 2006) then my actual savings will be more like £800 per year. Payback in 4 years.

Solar won't suit everyone. But for those of us on LPG its an option worth considering.

Solar water heating with a thermal store certainly is a better proposition than just DHW but is beyond the capabilities of most DIY.

However it all boils down to how much output in kWh your 30 tube panel will produce.

I had actually looked at Navitron and spoken to them. They are very reluctant to commit to the actual annual output of their panels.
Their 30 tube produces around 420kWh in June and about 35kWh in December and they say(verbally) that something between 2,000kWh and 3,000kWh per year in Southern Britain. It is worth noting that gas savings for the whole month of December will be approx £1 !!!

What is a little misleading is they say that their 30 tube panel will supply most of your hot water needs from April to Sept. Well if it can supply most of your needs of DHW in Sept when the output is much lower then it is probable that it will produce too much for you to use in June/July.

So I suspect that the useful output will be nearer to 2,000kWh than 3,000kWh.

No matter, let us assume for the sake of argument that it will produce 3,000kWh per year and you can use it all.

This is simply where your figures don't add up I am afraid.

You seem to make the assumption that whatever your demands the solar panel will provide it; and it won't! It can't!

Take your statement that you can save £400 in the 4 months from May to August. Your panel will produce no more than 1,500kWh in those 4 months(probably much less) so to save £400 you are pricing each kWh at over 26p

You could use an immersion heater on full daytime rates and produce that 1,500kWh at 10p for £150. If you used Economy 7 you could produce that for around £70.

You simply cannot pluck these figures out of the air and use them in your calculations.

So if your 30 tube panel can produce between 2,000kWh and 3,000kWh per year and you even resorted comparing that with full tariff daytime electricity for an Immersion heater your maximum savings will be £200 to £300 a year. Use Economy 7 and it will be much much less even allowing for the increased daytime tariff rate.

Now let us take your payback time calculations, which again I am afrad to say simply don't make sense.

The method you use is akin to saying if I have a £100,000 mortgage and pay £10,000 a year I will pay of my mortgage in 10 years. That would be true only if you could get a mortgage at 0.00%!

Even your very low £2,575 you paid for your DIY system has to be paid for from savings or the money borrowed.

Taking loss of interest on savings @5% that is £128.75p in lost interest a year.
So you will need to save that sum in reduced bills before you start to consider pay back time.
Now if you have gas, at current prices you will never save that sum from your bills so you your payback will be never!

You can take whatever savings you wish to use for full time Immersion heater use if you wish, and you payback time will be very long - and bear in mind your DIY efforts produced a system for half price.

Also everyone completely ignores all the maintenance involved with solar. Sure the panels themselves have a long life(Navitron say 'expected' life 25 years.) but all the other plumbing, pumps, electronics? Most firms seem to give them a 2 year warranty - I wonder why?

I have also read on a website that the small print for some firms requires an annual inspection or the warranty is invalid(I have not seen that myself - but it wouldn't surprise me)

What about the cost of anti-freeze replacement or the addition electronics required to prevent frost damage?

Sorry to appear so negative, but this is a Money saving website and savings and costs should be discussed.

The one card played all the time by installation firms is to make predictions of huge energy price increases in the future, and that unknown factor could certainly skew the figures toward solar - some of that offset by compounding the interest of lost savings.

More than happy to be challenged on my reasoning and figures above.

dekh

Cardew wrote: »

But please let us not even begin to base any economic discussion on the quite unbelievable figure of £340 p.a. savings.

Heh, my math is shaky anyway, compounded interest on the declining capital would probably be £1500 to £2000.

So I took most optimistic figures.

The bottom line. If payback is not gauranteed within the first twelve months it is very hard to make a case for this type of system.

Ample hot water in summer is a waste unless you are heating an outdoor pool, luke warm water in winter when you need it most?

I can't see a system like this lasting 13 years on our roof by the sea side. It is a foolish option.

People should remember that the figures quoted will also be for panels perfectly oriented south. (It wouldn't surprise me if the tests rotated the panuels during the day to keep pointing at the sun). Our "South facing" rear loses the sun at about 4pm in June and probably only gets a couple of hours direct line in winter as it tops the houses in front.

Payback on such a system? Never?

Now if you could unroll a sheet of panels the size of your roof for £50 and sell surplus electric back to the grid, then we are in business.

Otherwise you might as well nail a radiator to your roof and paint it black.

wpp34

As Cardew said, this is a money saving site and the arguments seem all against. (but I'm still tempted just to see what really happens!)

The variouls cost comparisons have made interesting reading as well but should we be taking into account any 'green' factors that might make a difference or would this be taken care of by changing to a 'green' supplier for my electricity?

Or are 'green' considerations out as they do not save any money?

dekh

Green is good.

Insulating significantly reduces energy consumption, saves money and reduces emissions.

I've yet to see figures on how many tons of CO2 are saved by using solar heated water and comparing that to the amount of CO2 used to manufacture, deliver, maintain and run (power pumps etc.) on this domestic scale.

So not sure about how green the grass is with this.

There is a forum dedicated to "Green Building" even there people say the amount of energy produced by domestic installation is miniscule in comparison with the actual domestic requirements and always at the wrong time of the year. One of the members stated that energy is gained more efficiently by passive solar heating - big south facing windows.

I think it is a fledegling, industry rife with cowboys, and experimental systems. A lot of fake figures and hype aimed at the middle classes who should know better.

We are looking at the equaivalent Of the IBM AT with 512KB memory for £3500 back in the 80's and we need the Dell (or insert other Manufacturer) Supadupa for £499.99. Except IBM were professionals, not that DELL aren't

moonrakerz

Gorgeous_George wrote: »

I got a flyer through the post for solar panels. I don't like flyers so I returned the prepaid 'come and mug me' card (uncompleted) so that they can use it again.

Not only am I green (recycling the card) but I help save the Royal Mail.



GG

You should have put Reader's Digest, AA, Which, Tesco, etc, etc name and address on it !

Cardew

wpp34 wrote: »

As Cardew said, this is a money saving site and the arguments seem all against. (but I'm still tempted just to see what really happens!)

The variouls cost comparisons have made interesting reading as well but should we be taking into account any 'green' factors that might make a difference or would this be taken care of by changing to a 'green' supplier for my electricity?

Or are 'green' considerations out as they do not save any money?

That issue has again been covered in some depth on the 'Green' Forum.

I have particularly been at pains to state that the environmental issues are very valid consideration.

However let people make up their own minds on how 'green' they want to be when they know the cost implications.

There are a number of posts where people argue that solar simply is not 'green' as the debit side of manufacture, installation, maintenance etc outweigh the credits in fuel saving.

I am most certainly not getting involved in that issue! I have enough on my plate!

P.S. I hadn't seen Post #66 when I posted the above!

shandypants5

Not sure if it would be cost effective or not, but I was thinking of making my own cheap and cheerful solar collector from a longish roll of black plastic water pipe.

My hosepipe gets really hot in the summer and itwould be nice to save some of that heat.

I am thinking of branching it off my existing outside tap leaving most of the roll still coiled, on my south facing patio.
Then teeing the open end into the incoming cold pipe of my hot water tank, with another couple of valves.

One to stop the existing incoming cold water, and one to blank off the plastic pipe so I could just detach it in winter if I had freezing issues, and go back to my existing house plumbing.

This would mean that all the water entering my hot water tank would be pre heated and take less gas to finish heating.

I know it sounds too simple....
Please feel free to tell me why it wont work.


GAHHH!!
I have just realised myself that my incoming cold feed goes to a ballcock in the loft tank!!
So that would mean I had a plastic tank full of hot water steaming up my loft.
Not good!

Back to the drawing board then..

dekh

shandypants5 wrote: »

Not sure if it would be cost effective or not, but I was thinking of making my own cheap and cheerful solar collector from a longish roll or black plastic water pipe.

..

I was serious about the painted radiator.

I can't find the website, but it has been done.

Couple of radiators from salvage, black hammerite, bright sun, lots of heat. Minimum of plumming, small pump, etc...

shandypants5

dekh wrote: »

I was serious about the painted radiator.

I can't find the website, but it has been done.

Couple of radiators from salvage, black hammerite, bright sun, lots of heat. Minimum of plumming, small pump, etc...

Yeah wasnt really thinking of a pumped system at all.
Just using the mains pressure and redirecting/splitting it so I had 2 incoming supplies.
One cold and drinkable, one hot/tepid and just to feed the hot water tank.

The problem I can see is that plastic loft tanks are not suposed to hold hot water. (I remember the one that split recently in the news scalding a child.)