Solar Power-is it worth it?

driller_killer

Some interesting posts here, some very vocal, some very wrong.

Firstly, there is no such thing as the average user.

Anyone considering this needs to look at how much DHW they are PERSONALLY using and forget some of the claptrap spoken on here about the "average house" The average house may be lived in by one person or five people and they will have vastly different usage.

I am unlucky enough to have LPG. (60p/litre) Since March 21st, we have used 402 litres. The central heating has not been on in this time. So, very roughly, we use 200litres per month just for DHW. I'll let Cardew do the sums on the rest.

Please look at this site:
http://www.solarenergy.ch/spf.php?lang=en&fam=1&tab=1
for some independent reviews on the efficiency of solar panels. Evacuated tubes and Flat panels are both considered. Evac tubes produce more DHW, perhaps around 680KwH/m sq.. [Wikora DF 100-6] (Most panels are 2m sq.); but more costly. Flat panels are cheaper, easier to maintain, but produce less DHW - 517KwH [Viessmann Vitosol 200-F]. In other words, evac tubes will make around 25% more DHW per annum, but at a greater cost. Whether you think this is worth it is up to you.

Of course, very few people have just one panel on the roof and much of the high upfront cost is from the installation. Adding another panel might cost around £500.


If you have got this far, well done.

The other things you need to remember are:
1) the proposed carbon credit card - if you smother your house in solar panels, you could sell your quota of carbon to someone else
2) the cost of oil and therefore gas/lpg/electricity is not going to come down. You can forget production getting stepped up. Only Saudi can do this and why on earth would they want to use up their greatest asset so quickly?

For me, a £4500 solar system that produces 50% of my DHW will take 6 years to payback based on my current system, assuming LPG remains at the same price for the next few years and Gordon doesn't throw in any "green" taxes.

However, the writing is on the wall for my LPG as i'm going over to wood pellets. On my current usage, it should shave around £1800 off my annual bill. This has the slightly bizarre effect of reducing the benefits of solar, making it 11 years to payback.

In essence, read and listen to what other people say, but do the sums FOR YOURSELF.

paceinternet

Hi, I'm new to the forum and trying to find as much info as possible to review our options.
Before reading this post I would not have believed solar had any chance of payback in this country.
My feeling was that Economy 7 for DHW would always be the lowest cost for both capital equipment and energy consumption.

driller_killer, you must be using a lot of hot water to be consuming that amount of lpg. Have you worked the lpg litres back to kwh to compare with your expected solar performance?

Gorgeous_George

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

driller_killer

Ha ha! I wish i was using a lot of hot water. Believe it or not, all that LPG produces is enough hot water for 1 shared bath between the kiddies and 1 shower each for my wife and I per day. That said, the second shower is lukewarm! Clearly, the system is inefficient.

It'll cost around £12000 for a new pellet boiler installed. 3 panels have been priced at £4100. I'm convinced of the former, but not the latter. I could go down the route of a condensing LPG boiler (£3000), but i think the writing might be on the wall for certain fuels. We seem to be being 'developed' back to the Victorian age.

In working out my solution, i'm trying to look to the future. Having been in the house for only a year, i do not intend to move for the next 15. (Quite like where we live!) We have two little children, soon to be three, so the things that i'm considering are:

1) My family will drastically increase its use of hot water as they grow up and to a lesser extent, heating
2) Future fuel costs. Will they ALWAYS go up? Well yes, i think they probably will
3) The weak excuse of a government that we have that cynically exploits anything to do with carbon in order to raise more tax.

Having done my sums, it'll be about 11 years for solar to payback (on a wood pellet boiler) at current consumption and costs. If we use more or fuel costs more or Brown taxes more, my time to payback will come down.

Is it worth it? Don't know.

Gorgeous_George

If I was to spend £3,000 on a solar 'anything' system, I'd need £172 in savings to match what I could earn by reducing my mortgage - and I'm on a good tracker rate of 5.74%.

That's £172 after all running/maintenance expenses.

Compare it to a ISA at 6.5% and I'd need £195.

Do it if you think it'll save the planet - but it won't - unless it is mandated at build IMHO.

GG

wpp34

Interesting 'advice' so far although some of it seems very aggressive to say the least.
My unbelievable savings were based on the figures that most suppliers of solar systems quote, ie 100% free water in summer and 50% free in winter. My direct debit for gas is around £70 per month at present and is bound to go up so I went for a 15% increase to £80. I assumed that on average half my gas went on heating water and reckoned on 5 months 'summer' and 7 months winter (why no spring or autumn?). This gave me 5 x £40 + 7 x £20 =£340. I would agree that my research has led me to figures of £50 are more realistic.
The posts so far have persuaded me to find out a few more facts about my DHW heating, namely what proportion of my gas do I actually use on the water alone. I'm not exactly sure how to do this but will start with assuming 4 baths, 1 wash at 40 C in washing machine and 1 dishwash at 55C in dishwasher plus whatever I should allow for extra use of DHW on top. As Cardew seemed to think that my gas consumption of 1500 kWh per month was way above average (although I did not say it was all on DHW, especially as we have a gas hob) I will also investigate the possibility that my gas meter is faulty, it is very old!
If most of you are to be believed then the figures that Solar Heating suppliers are quoting are way out of line.
Now dare I ask if I should replace my old, open coal fire with a woodburning stove or a modern convector or cassette fire.....

Cardew

driller_killer wrote: »

Some interesting posts here, some very vocal, some very wrong.

Firstly, there is no such thing as the average user.

Anyone considering this needs to look at how much DHW they are PERSONALLY using and forget some of the claptrap spoken on here about the "average house" The average house may be lived in by one person or five people and they will have vastly different usage.

I am unlucky enough to have LPG. (60p/litre) Since March 21st, we have used 402 litres. The central heating has not been on in this time. So, very roughly, we use 200litres per month just for DHW. I'll let Cardew do the sums on the rest.

Please look at this site:
http://www.solarenergy.ch/spf.php?lang=en&fam=1&tab=1
for some independent reviews on the efficiency of solar panels. Evacuated tubes and Flat panels are both considered. Evac tubes produce more DHW, perhaps around 680KwH/m sq.. [Wikora DF 100-6] (Most panels are 2m sq.); but more costly. Flat panels are cheaper, easier to maintain, but produce less DHW - 517KwH [Viessmann Vitosol 200-F]. In other words, evac tubes will make around 25% more DHW per annum, but at a greater cost. Whether you think this is worth it is up to you.

Of course, very few people have just one panel on the roof and much of the high upfront cost is from the installation. Adding another panel might cost around £500.


If you have got this far, well done.

The other things you need to remember are:
1) the proposed carbon credit card - if you smother your house in solar panels, you could sell your quota of carbon to someone else
2) the cost of oil and therefore gas/lpg/electricity is not going to come down. You can forget production getting stepped up. Only Saudi can do this and why on earth would they want to use up their greatest asset so quickly?

For me, a £4500 solar system that produces 50% of my DHW will take 6 years to payback based on my current system, assuming LPG remains at the same price for the next few years and Gordon doesn't throw in any "green" taxes.

However, the writing is on the wall for my LPG as i'm going over to wood pellets. On my current usage, it should shave around £1800 off my annual bill. This has the slightly bizarre effect of reducing the benefits of solar, making it 11 years to payback.

In essence, read and listen to what other people say, but do the sums FOR YOURSELF.

Interesting website.

However it really confirms what I have been(admittedly vocally - guilty as charged!!) saying and is in line with the UK government sponsored tests(in Richmond nr London) that produced around 1,000kWh from a single panel system.

The solar panels in that website give around 500kWh per sq mtr per year. The 2 sq mtr panel will give, if my 2 times table is correct, around 1,000kWh per year. Put in another panel and it is capable of producing 2,000kWh per year. If you want, lets add another panel(6 sq mtrs) and it will produce 3,000kWh per year.

Most of that will be produced in the summer and the majority of people will not be able use all that hot water in the summer.

However even if they did use the whole 3,000kWh, what will that save them?
If you have gas, what will that cost? let us say 3p for a kWh(to allow for boiler efficiency) so it will save £90 per year. Make that 4p for a kWh and that is £120 per year.

Surely the point is quite clear that the savings are only a fraction of the £340 that the OP(wpp34) is considering.

If you think giving the average UK consumption of energy to produce DHW 3,000kWh is irrelevant - then fine.

If you use 15,000kWh per year for DHW it still boils down to how much HW your solar panels can produce, and how much of that you can use.

So I still maintain that for most systems a saving of £50 a year is good(if you have gas) - with oil you can double that saving. Although as I said above, Economy 7 starts to be an option with oil at 60p/ltr.

Now I can't possibly see how any DHW solar system can begin to pay you back £4,500 in 6 years. Even taking a simplistic payback(i,e. ignoring the interest on borrowing £4500) you are talking about solar DHW saving you £750 a year, and that you are spending £1500 a year on DHW!!

You have implied I have been talking claptrap, and I have kept my response civil.

If you feel any of what I have said above is incorrect, could you please enlighten us with some figures - as you stated you have 'done your sums'

Specifically what output do you envisage from a solar DHW system and how much of that DHW will you use.

What price do you place on each kWh.

Please be specific.

Rather than use the word 'claptrap' I suggest that your 'sums' on solar are in error!

Cardew

wpp34 wrote: »

Interesting 'advice' so far although some of it seems very aggressive to say the least.
My unbelievable savings were based on the figures that most suppliers of solar systems quote, ie 100% free water in summer and 50% free in winter. My direct debit for gas is around £70 per month at present and is bound to go up so I went for a 15% increase to £80. I assumed that on average half my gas went on heating water and reckoned on 5 months 'summer' and 7 months winter (why no spring or autumn?). This gave me 5 x £40 + 7 x £20 =£340. I would agree that my research has led me to figures of £50 are more realistic.
The posts so far have persuaded me to find out a few more facts about my DHW heating, namely what proportion of my gas do I actually use on the water alone. I'm not exactly sure how to do this but will start with assuming 4 baths, 1 wash at 40 C in washing machine and 1 dishwash at 55C in dishwasher plus whatever I should allow for extra use of DHW on top. As Cardew seemed to think that my gas consumption of 1500 kWh per month was way above average (although I did not say it was all on DHW, especially as we have a gas hob) I will also investigate the possibility that my gas meter is faulty, it is very old!
If most of you are to be believed then the figures that Solar Heating suppliers are quoting are way out of line.
Now dare I ask if I should replace my old, open coal fire with a woodburning stove or a modern convector or cassette fire.....

My 'aggressive' comments on the 'unbelievable figure' were not aimed at you, so my apologies if you thought they were, but at the salesmen who peddle such rubbish.

As I said in the post above this; it really doesn't matter how much DHW you use.

The only criteria to use is how much DHW the solar panels produce and how much of that you could use in the summer months when most of it is produced.

There can be no doubt that a ballpark figure for any 2 square metre panel is around 1,000 kWh a year. You know how much you pay for gas and you can work out the savings. You will need also to know the efficiency of your boiler.

Afternote.
Regarding the claims of the solar manufacturers that they provide all the DHW in the summer and half the DHW in the winter.

If you take the average output of 2 panels(4 sq mtrs) there can be little doubt the output will be approx 2,000kWh per year.( I hope nobody disputes that)

Looking at several sets of figures it would appear that the average energy produced in the 6 summer months is approx 80% of that(1600kWh) and 400kWh in the winter.

Now given that the average house( I could define the term average if required!!) uses 3,000kWh per year on DHW(approx 250kWh per month) it is reasonable to claim that all the summer DHW could be produced by solar.

However the bottom line is that the maximum output is still only 2,000kWh per year.

driller_killer

Cardew, you would do well to read my posts more carefully before you fire off a reply. I referred to you once in the whole of my post (and that was inviting you to do some sums on my figures), yet you think that that whole post was a diatribe against you. However, if you want me to pick you up on some of your figures, i will gladly do so. Firstly, in your reply yesterday to wpp34, you said "i don't understand what you mean by power" I think that rather rude, as you clearly do understand what the poster meant. However, you then went on to say that "Energy can be measured in kWh" The SI unit of energy is the Joule, not Watt. Watt is the SI unit of Power. So, if you're going to pick posters up on their terminology, make sure you get yours right first. Ok, pedantic, but i thought you rather blunt to the poster.

In many of your other posts, you talk about "borrowing £4500 at 6%" to pay for a system and base of lot of your calculations on that. Others talk about the value of the APR on their savings. Yet people seem to forget the erosive effects of inflation, currently 4.2% [RPI] source IDS, 13 May 2008.

Some of us will not be borrowing to pay for a solar system; we would instead be using that much forgotten thing called "savings". My current rate of interest is 4.8% Therefore when inflation is taken into account, the interest i am actually is receiving (4.8-4.2)=0.6% On £4500, this is £27. Then i will be taxed on that, leaving with me around £21. So, by leaving my money sitting in the bank for 10 years, i will be better of (in today's prices) by £210. Isn't it interesting what inflation does. If your circumstances are such that you are borrowing to put the panels on your roof, i would politely suggest that you would do much better to pay off your mortgage before adorning your house in glass tubes.

In 1997, the cost of barrel of Light Sweet Crude oil adjusted for 2007 prices was £19.04 - source WTRG Economics. According to the same company, yesterday it was £131.03. That is a 688% increase in 11 years. And before anyone picks me up, yes i know Light Sweet Crude is used for petrol, not necessarily heating oil, but i'm using theses figures to highlight a point. I know world circumstances may have forced a lot of this, but who's to say that the next 11 years will be any different. That means by 2019, the price of a barrel would be $900. In today's prices (i.e. factoring in inflation at 4%), it would be around $340. As most of our conventional heating is intimately linked to the price of oil, the writing would appear to be on the wall.

British Gas charges 4.1 to 4.8p per kWh. It isn't possible to equate the cost of mains gas or LPG per kWH to electricity since this negates the efficiency of your boiler. Using electricity to heat water is extremely efficient, but this is reflected in the higher kWh price. If you have an old boiler, you would need to perhaps applying an efficiency factor of 60% for it to provide your DHW. This would mean that you're losing 40% of the gas you're using through the inefficiency of the boiler (around 1.9p per unit). Therefore, a 60% efficient boiler would in effect be 6.7p kWh.

For those wondering so pointedly about my sums, here they are.

Firstly, the background info:

I live in a 5 bedroom house. There is me and my wife and 2 children (at the moment), both under 3. They have a shared bath each day, filled to a depth of 6 inches. My wife and i have a shower each per day lasting 8 minutes and 10 minutes respectively. It is not a 'power shower' At the end of the second shower, the water is lukewarm. We have a dishwasher rather than washing up. I think on these figures, our consumption of DHW is low compared to other families.


On the 20th March, our LPG tank was filled up
On the 21st May, it was filled up again. 402 litres were delivered.

That means in 2 months, we have used 402 litres. Lets call it 400.

In this time, the central heating has been off, therefore all of this LPG has been used to provide DHW.

400l / 2 months = 2400l per annum.
At 60p/litre, this costs £1440.

Cardew, i have used your figures of 3 solar panels being able to supply 50% of the DHW, which i happen to agree with.

50% of my annual bill for DHW is £720.
I have a quote for a 3 panel system of £4100.
Therefore £4100/£720 tells me how many years to break even. - 5.7 years.

Awesome eh?

Except, well no, not actually. In working out these figures, it was painfully apparent that the reason i was using so much LPG was that my (old) boiler was woefully inefficient and was consuming vast amounts of LPG for not much. This gave what you might consider an artificially short payback time. This actually is the correct payback time, but the reason i have stated it is 'artificial' is that only an idiot could not see the wood for the trees here. It is the boiler that is in fundamental need of action. By switching to wood pellets and getting a more efficient boiler, the payback time of adding on solar panels suddenly goes up to 14 years.

I have spent some time considering my situation and would suggest to others that you weigh up issues related to your personal circumstances. I would bear in mind these points:

If you're intending to move house in less than 10 years, forget it
If you're on mains gas and don't mind a payback of around 12-15 years, then consider it
If your boiler is old and inefficient, replace it before considering panels
Will your consumption of DHW increase over the next few years? - i.e., is your family growing. The 'post-school' shower is well provided for by solar panels
Those on Oil and LPG might like to consider panels - perhaps being a minority in that we are off the national grid, the high prices of these fuels means payback of sub 10 years is not far off
You will generate less Carbon. If this is important to you then great, but i would also ask you to consider the actions of the government regards Carbon and taxation and not just now, but 10 years in the future.


Anyone thinking of slapping panels on their roof needs to look on it as a really long term view. The headline grabbing figure of 5.7years payback is just the sort or tactic dishonest companies use. Also forget about people quoting you "averages".

The average number of children per family is 1.8 source BBC news 6th Novmber 2007. Anyone have 0.8 of a child?

Its a bit like the statistic (fact) that says the averge number of legs a man has is less than 2. (work it out)

So to repeat myself, do the sums for yourself, don't RELY on others. Seek an opinion, but question is what they're telling you correct. Solar Panels are NOT likely to benefit the vast majority of people for some time, but i, nor anybody else in this forum can advise YOU, the reader of this whether they are right for YOU. But as power prices rise, more and more people will start to be tipped into considering them financially viable.


And my decision? Well, still haven't totally made my mind up, but i am blessed enough to be able afford the installation. I am going to have a very long payback time, but in combination with a pellet boiler, it should mean my carbon footprint is much smaller (pellets are classed as renewables), therefore it enables me to stick two big green fingers up at Gordon Brown. And the value of that? Priceless!

Cardew

driller_killer wrote: »

Cardew,

snip
!

Firstly, I am fully aware of the correct terminology for units of Energy. What I stated was

“Energy produced by Gas, Electricity, Oil or Solar can be measured in kWh. Thus the normal measure of energy for producing DHW is given in kWh.(because that is how we pay for energy)”

Nothing wrong with that! They can be so defined.

As the OP said he 'wasn’t interested in the power the systems produce but how much hot water,' I genuinely did not know what he meant; indeed I thought he might be confusing solar electricity generation with solar DHW.

So your assumption/accusation of rudeness was incorrect!

Secondly British gas do not charge “4.1p to 4.8p” Their standard tariff price for all secondary units(after the first 1,143kWh per quarter) is either 2.391p or 2.709p and on their Click 5 it is 2.601p – after first 670kWh per quarter(all prices include VAT but exclude discounts)

I did say you need to factor in boiler efficiency a couple of times - if you wish to read carefully.

Let us get to the more important issue.

Cardew, i have used your figures of 3 solar panels being able to supply 50% of the DHW, which i happen to agree with.

I quite like that quote – I don’t think I have seen one more out of context – you must have political ambitions!!! And you accused me of not reading posts!!

The 50% is of DHW is for a house using the UK average of 3,000kWh per year.

I have gone to great lengths(using the data you provided) to say that a 3 panel system will produce approx 3,000kWh.(you are presumably not going to dispute that figure?)

Somehow you manage to get that 3,000kWh to be worth £720 and base saving calculations on that figure. So you are pricing each kWh at 24pence!! –
That makes Economy 7 electricity and an Immersion heater seem a bargain at around 4p/kWh!

In the real world I suspect you won’t be able to use some of that DHW in the summer.

I won’t even dignify your simplistic economic calculations by explaining how silly they are – I suspect you won’t fool many!(we can discuss those calculations separately if you wish)

I asked you:

Specifically what output do you envisage from a solar DHW system and how much of that DHW will you use.

What price do you place on each kWh.

Please be specific.

You have studiously avoided any answer.

P.S I have no mortgages and am not contemplating getting either solar heating or electricity; but thank you for the advice!