Solar Panels - verifying the numbers

I guess that this is off topic but I suspect that I will find some experts here.

My sister has had a man around to quote for this and I've been tasked with checking out if what she was told makes sense.

She has a bungalow with a shallow sloped roof and the quote was to install

14 panels on an Easterly facing roof because the Southerly facing one is shaded by a tree. So the figures are:

Expected output 2928 kWh per year.

Returning 41.3 feed in tariff plus a saving on her electric bill of 50% of the output at say 12p and the other 50% output gains 3p from the electric company.

The prices are:

a) A "leasing" scheme whereby the householder pays an "installation" fee of

2610.00 and receives the "free electricity plus the "3p" but the company receive all of the 41.3 feed in tariff.

b) Outright purchase costing 18237.00 whereby the householder keeps all of the returns.

I calculate that (a) returns around 220 pounds (8.4%) and (b) returns 1430 pounds (7.8%).

So the question is, are these figures actually achievable and is the cost price competitive?

Does anybody know?

tim

Reply to
tim....
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also ask yourself how long the output will stay at those levels with dust, birdshit, and general wear and tear.

And how long the government will tolerate buying micro amounts of electricity at 20 times the bulk price from a nuclear set.

Reply to
The Natural Philosopher

How much extra would be gained by chopping the tree down? i.e. how much is that tree worth.

So far as calculating the returns, did you take into account the "lost" income from having the difference - £15,600 in the bank earning interest? Even at 3%, that's nearly another £500 / year.

My inclination would be to let the supplier take the risk of not meeting the expected output, or of a future govt. reducing / removing the subsidy (as happened in Spain recently).

Reply to
pete

In message , pete wrote

And any money "made" by selling the electricity back would be classed as taxable income.

Reply to
Alan

Ask on what basis they arrive at the expected output. I think you will find its a back of an envelope calculation based on theoretical maximums which are never achieved in reality. Not using a South facing aspect is going to approximately halve the available energy so either the tree goes or forget it in my opinion

Reply to
cynic

I agree with all the other posters to date. From what you describe, keep the money in the bank earning interest which will be greater than the income and still be an asset.

Reply to
Clot

It's not her tree!

Obviously one looks at this in totally. That's 6-7% instead of 2-3 %

Reply to
tim....

Is it?

(I really don't know, but it would seem to be too complicated if it were because you'd be allowed to deducts all the costs first)

Reply to
tim....

They need cleaning once per year. I don't think that there's any "wear".

They "promised" 25 years, but this is a risk!

Reply to
tim....

Ask on what basis they arrive at the expected output. I think you will find its a back of an envelope calculation based on theoretical maximums which are never achieved in reality. Not using a South facing aspect is going to approximately halve the available energy so either the tree goes or forget it in my opinion

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It seems to be 10% of the theoretical maximum.

The panels are rated at 230 Wp (whatever the p is) and I assume that's per hour.

230 W* 14 * 24 * 365 is 23000 kWh per year. (of course that includes night time!).

I assumed that the supplier took the orientation of the roof into account. It is quite a shallow slope it will still get the sun for most of the day, it just wont be direct. It is in his interest to do this if she goes for the "lease" option which I think is the favourite ATM, the ROI on the 18,000 doesn't look good enough given the risks.

tim

Reply to
tim....

Expected on what basis? (tell us the panel area, roof slope and approx. location (nearest city) and someone will be able to check the numbers)

What's the cost of capital? (lost interest)

If she has a mortgage the interest rate on the capital is of course the mortgage rate. IMHO this will soon rise and she may prefer to pay off the mortgage and know where she is, rather than effectively borrow money to buy the panels.

Andy

Reply to
Andy Champ

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "tim...." saying something like:

Output falls from day one. Ten-year-old PV panels can be producing half of what they were when new, but it depends on the solar tech involved. As always, the technology is steadily improving, but I really don't know if it's worth it yet. Fine, if you live in an off-grid cabin in the woods, but otherwise, probably not.

Reply to
Grimly Curmudgeon

The rule in investment is...

#1 Multiple Asset Classes

Achieving decorrelation such that when A-B-E go down C-D go up. Only in 2008 did this fail, but it was momentary and something like M&G International Sovereign evidentally found a flux capacitor and decided to give near 18yrs return in 1yr.

An example would be a) Cash (liquid and reduces portfolio volatility) b) Gilts, International Sov Treasury, Index Linked UK & International Treasury (with the emphasis on Index linked) c) Corporate Bonds (with emphasis on global exposure) d) Equity Income (with emphasis on global & emerging market exposure) e) Commodities (with some emphasis on oil/ energy if she pays a lot out, Gold is rather pricey now and "a bit late unless Werner Republic") f) Global Commercial Property Shares (NOT actual property because it is illiquid and NOT solely UK) and g) Currency Hedge Funds (Insight do one, they make money on extreme currency moves, many do badly though). Increasing age skews emphasis to a) & b), otherwise realise only shares outperform inflation significantly unless you are very lucky (buying 30yr T-Bills yielding

12% decades ago was a bright move and one the USA would like to avoid repeating).

#2 Built Monthly

That way you Dollar Cost Average over time. The exception is if market conditions provide a significant drawdown opportunity - such as a 3 standard deviation or greater drop. Such are rather common re 1987 1998 2000 2001 2002 2007 2008 - there is always another around the corner and that will remain the case going forward.

#3 Risk Adjusted Return

I would not suggest b) unless she has at least 100k of liquid capital. The reason is the percentage return is barely better - it just requires more capital, thus there is little compensation for the risk taken on. You do not accept a risk without a commensurate premium and I do not believe the yield of b) is commensurate, I would want at least 14%.

#4 Market Pricing

By that I mean sufficient volume so price accurately reflects supply- demand. To be blunt the projected yield is not guaranteed and is based on assumptions, those assumptions need to be subjected to a sensitivity analysis. A sensitivity analysis is basically a "best, likely, worst case scenario" and frankly I would not be surprised to see 5% being a more realistic real world figure.

Now, 5% sounds good, but consider Fidelity MoneyBuilder Income which is a AAA Corporate & Other Bond fund will give you an annual yield of circa 4.5%. It is true such income can at times (effectively) come from capital in that the capital portion of your holding is subject to variation, however you can *liquidate your position* and recover at least 80% of your cash at any given time. Can you do that with a pile of solar panels on your roof? This is why b) is a very unattractive option and to be honest a) is not remarkable unless someone would otherwise put =A32610 in Premium Bonds (which have a return that is low).

The real problem going forward is not so much interest rates, but inflation. Looking at Lib-Con figures it is very likely that inflation by stealth is on the cards to erode the debt - which means your solar panel yield needs to be considered in relation to that. That is why a) may look attractive now, but in hindsight could be the next bunch of people whining on TV about how they got stiffed out of their life savings.

So overall, any investment should be made with consideration to Risk Adjusted Return and form part of a multi-asset portfolio. A golden rule is your age as a percentage of assets in Gilts/Global-Treasury/ Index-Linked Global Treasury. USA is going to run down Index Linked Debt over the next few years because it plans on burning the 22T$ liability by inflation, most likely by forcing more pensions/banks/ individuals to buy the stuff - but in non-index linked form.

The future is about capital preservation AND capital preservation relative to living costs.

The worst thing you can do is bet on one thing - that exposes you non- diversified risk and missed opportunity. Today Stocks went down about

2% whereas Sov Debt probably went up 0.7-1% - you have more Sov Debt than Stocks so the portfolio figure barely changes, but you sell some Sov Debt (sell high) to buy some Shares (buy low) on a regular basis so you benefit from the volatility between asset classes whilst at the "headline balance level" you get reduced volatility. The exception was 2008, but that was an exception because "2T$ money has to go somewhere" in that it rotates into liquid assets and cash is generally not one of them at the global view.

The real pig is Cash yields so little, but even ING will give you about 2.75% right now. An issue is inflation, I do not see interest rates rising in 2011 to protect currencies - I think they will delay it until 2012 due to the risk to GDP. They must get GDP up, but inflation increases cost of debt which in turn reduces GDP so they can't let inflation get too high :-) Re housing, remember bottom of the 1981-1990 channel is about 67,000 for avg house price. Without jobs even immigrants go home and that along with C/C debt writeoff is making banks distinctly "ill".

Another issue is tax rises reduce GDP very effectively, so all in all we are stuffed. Beware "easy quick solutions", it takes prudence over a decade to built up a portfolio *monthly* because that way you iron out the very obvious lunacy. Trustnet has a good multi-fund (indeed anything) charting tool. Avoid individual stocks unless you are willing to buy core names, accept 30% will vanish (even Mer & Lehman did, and GM is basically Gov't Motors), and stick with buying them for

20yrs or so - even then you will not pick the next AAPL because it is most likely in an emerging market which will either be bought by the Western company so diluting the return potential or buy the Western company for eventually peanuts). All Western Big Business dies in the end because of the failure to manage change, so funds are a far safer option - it just requires more monthly saving to compensate for the reduced annual return, then let years of compound interest do their thing.

So comes down to her existing financial circumstances.

Reply to
js.b1

p is "peak", in other words the maximum the panel can achieve at the correct angle pointing at full sun and artificially chilled . It is in practice never achieved .

With a non-tracking system on an easterly roof the figures quoted are wildly optimistic. Typically an optimally sited solar PV panel will achieve a peak output roughly half its "p" value. Face the panel east and that nearly halves again.

Most greenwash wind/solar companies are out and out frauds run by people the double glazing industry cast out as undesirables.

As a rough guide 1 sq m of panel, optimally aligned will receive 1mW of energy per year. Solar panels are typically about 15% efficient at the most (many sold in the UK are about 10% efficient) so 1m2 of solar PV facing south with a clear sky cannot produce more than 0.15mW in one year. Assuming each panel is 1sqm that is an absolute maximum of

2.1mW per year (which is probably where the shysters got their 2.9 mW from with a bit of imagination).

Facing east and at a less than optimal angle takes at least 50% off that so 1mW per year is probably closer to what will be achieved in reality.

The leasing scheme means she will probably get nothing back but be lumbered with "annual maintenance" costs. She needs to read the contract (probably printed in 5pt gray on gray) with a good magnifying glass.

The outright sale simply means she will lose a lot of money straight away.

In your calculations of return don't forget that the capital is lost with the solar panels. After somewhere between 10 and 20 years they will be worthless and need replacing. If the house is sold the panels will add a small amount to its value but nowhere near their original cost.

Reply to
Peter Parry

Crazy scheme. Solar PV on south facing roof on a grid connected house makes no economic sense at all. If it did they'd be going up all over the country. Putting them on east facing and pretending it makes any sense is simply a disingenuous sales pitch.

There is a blip in the picture, which is that a govt scheme is giving high payback currently, but its hard to see how that will last long.

Run, run away from the con artists.

NT

Reply to
NT

Just chop the tree down and burn it. Probably produce more energy than the solar panels.

Owain

Reply to
Owain

Well one milli watt is not even a unit of energy.

Its a unit of power, and even a fly can generate that much.

Reply to
The Natural Philosopher

If it's any help, the weather records for my part of the sunny south-east shows that 2009 got 1695[1] hours of sunshine. Presumably these panels can generate some (how much?) current in overcast conditions - and even when the sun has gone past south, which would put it out of sight from your proposed panel positions.

[1] Last year was considered quite sunny. A better average is 1500 hours
Reply to
pete

P is for peak, so this figure is the peak output. Time is irrelevant.

I strongly suggest that, if she is serious, she gets a number of quotations. You will get wildly different offers.

AIUI, the performance figures are produced in line with officially laid down calculations. The quotes I have had, for a SSE facing roof, are all pretty close to a ratio of yearly output kWh = 0.8 x peak installed power. In your case this figure is

3.22/2.928 = 0.909 I don't believe it for an east facing roof.

As to the overall cost, your figure gives £5663 per kWp installed. Again this is at the expensive end of the scale, and I have had a number of offers below £4000 per kWp.

A lot depends upon the panel manufacturer, the (very) small print of their performance guarantee, which you will find to be far less generous than it first seems, and how likely you think it is that they would still be trading if you came to claim against them in 20 years.

Chris

Reply to
Chris J Dixon

And the company is demanding close to £20,000 for the installation? The panels required (14 x 210W) retail for £4,200. The grid tie inverter required for the feed-in costs £1000, retail.

So the company are charging somewhere around £14,000 for installation.

That's a rip off of impressive magnitude IMO. If they got that down to £5K, with an installed price of £10-£11K it would be worth it.

It would certainly be better to DIY.

Reply to
Steve Firth

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