My solar PV first year payback calculation

Cardew

Fred,
It is good news that the £2,500 grant is still available.

Playing the 'Devil's Advocate' (or Solar Sceptic) I have been doing a little research today and a few other points to consider.

1. freddix has covered the provisional nature of the proposed FIT tariff, although I would be surprised if the proposals were not accepted.

2. Your calculations assume that you will use all your generated electricity and have costed that at 10p/kWh inflated @5% - that clearly is not correct. How much you will export is yet another 'wet finger in air' guess, but an example in the Government website gave 40% as exported.

3. I really think that it is improbable that a system with electronics, connectors and cables etc is going to last for years and years without expensive repairs. If it is so reliable, why only a 2 year warranty on the system?

4. The latitude of the site makes a big difference to the output. Whilst you in London will be better than the UK average, those in the North will have considerably reduced output.

5. Lastly, and perhaps most importantly, is the cost of a fitted system. The websites talk of a figure between £5,000 and £10,000 per kW.

I have phoned a couple of approved installers and, whilst reluctant to discuss costs on the phone, all indicated that for small installations of less than 2kW that £7,000 per kW would be the cheapest price.

Your calculations have(understandably) used the OP's figure of £7,950 for a 1.44kW array. It is not clear how long ago his was installed - but obviously over a year ago.

All the indications I have are that you would be lucky to get such a system today for under £10,000.

I appreciate I have deliberately painted a negative picture.

However the only factors that would swing the calculations in 'your favour'(the solar enthusiasts!!) is if electricity costs inflated at over 5%pa(and that is not a big factor in the calculations) and long term interest rates were to be less than 4% net - and it is very easy to fix that rate now for several years ahead and the economists(with their track record - what do they know!!) all indicating that rates will rise.

yakky58

Not sure if this helps or confuses the issue. I have a 2kwH array.

Over the past year ....

Start of record = 9171
End of record = 12424
Total inducted from grid = 3253


Total generated over that period = 1924
Total I used of generated khW (calculated by each months total generation - exported units) = 1140

So total used = 3253 + 1140 = 4393
That means I exported over a year 1924 - 1140 = 784
Thus I got 784 units worth off the bill.

I have been careful to reduce usage to maximise benefits of generation but I got paid for 784 units...plus 2 ROCs which I sold back to SSE.

Will get better when an expensive teenage leaves and I don't have to switch off his electrical goods.

Total cost of installation for 2kwH array was £8500 ish

I make it over 40% of electricity i used is self generated. That looks a good deal to me. Been up and running for 3 years zero maintenance aprt from washing them 2x a year which is not big deal. It seems to make a difference when the dust is cleaned off I get about 100w/hour more but that maybe me being optimistic.

Cardew

yakky58 wrote: »

Not sure if this helps or confuses the issue. I have a 2kwH array.

Over the past year ....

Start of record = 9171
End of record = 12424
Total inducted from grid = 3253


Total generated over that period = 1924
Total I used of generated khW (calculated by each months total generation - exported units) = 1140

So total used = 3253 + 1140 = 4393
That means I exported over a year 1924 - 1140 = 784
Thus I got 784 units worth off the bill.

I have been careful to reduce usage to maximise benefits of generation but I got paid for 784 units...plus 2 ROCs which I sold back to SSE.

Will get better when an expensive teenage leaves and I don't have to switch off his electrical goods.

Total cost of installation for 2kwH array was £8500 ish

I make it over 40% of electricity i used is self generated. That looks a good deal to me. Been up and running for 3 years zero maintenance aprt from washing them 2x a year which is not big deal. It seems to make a difference when the dust is cleaned off I get about 100w/hour more but that maybe me being optimistic.

Certainly doesn't confuse, and as usual is a precise set of data.

For those who haven't read yakky's previous posts, he carried out much of the installation/preparation for his solar array himself,(and 3 years ago) so a figure of £8,500 for a 2kW array is not representative.

The figure of 1,140kWh(60%) exported from a total of 1,964kWh leaves 784kWh( 40%) to be used in the property. This re-inforces the point made above that you cannot use the total generated output in savings calculations at full price + inflation(10p and 5% in Fred's example)

It also makes the point that cleaning is required for full efficiency - particularly in East London - and many will not want to climb up on roof to clean panels.

yakky58

Hi Cardew,

Not sure I follow your reasoning.

1924 is the total I generated over the year. Of these I used 1140 of them myself, so they were free and not paid for.

The 784 unused by me and exported to the grid I got paid for by SSE off those inducted.

So total inducted was 3253 - 784 = 2469 (namely that's what I paid for in a year) isn't it? That's what SSE got paid for.

Now as I qualified for 2x ROCs these were transferred to SSE and they deducted that off my bill. I got £120.00 for those.

So take that off the bill.

So isn't the saving, in simplistic terms what I would have paid for 4393 kwH to what I did pay for 2469 - £120?

Plus my time to clean... this week last of years clean...that's 25 minutes with a hose? Minimal.

My plan is to reduce 4393 to 3500 next year, mainly through the loss of last teenager and some further efficiencies. Assuming same production of 1924 that would be 1576 - say another 2x ROCs that would be bigger savings.

Isn't that what the true savings are?

By the way I put away the savings in my a 4.65% account so I roll back and gain compound interest.

Lastly you seem to make a lot about cleaning, that is only me being fastidious I can not give accurate figures whether clean is of benefit. I only think I see a benefit it depends on the sun as well.

Cardew

Hi Yakky,

Sorry I misread your figures and transposed the exported/used totals.

So the position is you exported 40% of your generated electricity.

So isn't the saving, in simplistic terms what I would have paid for 4393 kwH to what I did pay for 2469 - £120?

Certainly you are correct for your pre-FIT system.

I was using your figures in the context of fredbears's(and the OP's) calculations where they had assumed that under the post FIT regime that all generated electricity would be used in the house; and the costed this in their saving at the present price(10p inflated by 5%.) using your figures 784kWh would be sold to the electricity company.

I am not making a big deal out of cleaning - merely to state it is a consideration.

albyota

If it interests anybody, las night I actually applied for and was successful for my LCBP grant of £2,500 for Solar PV, it expires on 10/01/2010, I also called two companies to get quotes over the phone for 2kW installation grid connection, one was £9,800 + 5% Vat other was £10,300, the difference in price was the distance first company was 12 miles away second one is 100 miles away. the expensive bits are the panels at about £430 each (11 x 185W required for 2kW), the framework brackets about £300, the electronic inverter costs £1,250, the cables aren't that expensive but have allowed £100, but the scaffold can cost anything between £500 and £1,200 (say £750) and the the labour on top probably £900. the grid connection 2 way meter costs between £45 and £75. plus company markup at about 20% so roughly £9,726 + 5% Vat = £10,213 minus the £2,500 would be £7,712 it seems prices vary quite a bit as to get their MCS accreditation cost a fair amount, so would still be trying to recover this from the early adopters, I'm still undecided as I would need to finance this, and as the mathemeticians all say there are better ways to get ROI, I may have to wait till the price comes down a bit! I shall continue to get quotes, to check out the market competition in a downturn.

Mcfi5dhc

Update for all - I've had my Import/Export meter fitted today. Took about half an hour and replaces my old dial meter. Its much smaller than the old one, not really had a decent look at it yet.

So in a week or two, I'll have a good idea of what I export (I cannot just assume that this weeks figure is the same throughout the year, as I need to build in daylight hours).

As an FYI, I have never assumed I use 100% of the power - I do leave the house sometimes!

To export power, you don't need to generate more than you use over a year - you just need to generate more than you use for a sustained period of a few minutes or more (though really a couple of hours or more). So, if over 10 daylight hours I generate 6 units, but the freezer/Skybox/doorbell only use 1, I have exported 5 units.

My commission date was 31st July 2008, after a 3 day installation.

Albyota - good news about the quotes. Have you thought about 0% BTs on credit cards matched with matched betting (just look on the rest of the MSE forums)? Both are easy to do, and it means you won't have to dig into your savings. This would be the best of both worlds, though to me I was happy with the payback of approx 10-13 years, and I still am. I used a 0% card for mine, and use matched betting for other stuff (currently saving for another car, should have enough by next year).

A_fiend_for_life

I am pro solar even though it is expensive compared with mains energy this is partly because I think current energy production doesn't factor in the externality costs.

The very problem that solar should be addressing is that of reducing emissions. Do any of these companies provide the carbon footprint of their kit?

daytona600_2

8 x 180Wp panels gives total of 1.44kw
but at £ 7950 your supplier is wearing a mask
i supply 1.44kw system for £ 4999 less grants

for complete ready to install system
pv panels , inverters , roof mounting system all installation equipment

certified to MCS - microgenerationcertification for low carbon buildings
grants £ 1000 to £ 2500 - £4000 in scotland , more for charities 50% +
grants would cover installation
8 x 180wp pv panels is only £ 2448
26 x 180wp pv panels is only £ 7995 4.68kw

your payback time would be vastly reduced
for £ 7950 would supply complete 2.8kw system with 16 x 180w panels

if you need any more information on how your roof is the best investment
spend £10.000 on pv system will generate £30.000 in next 25 years

scott

Mcfi5dhc wrote: »

I've had 8 x 180w Sharp Solar PV panels on my roof for one year now.
I see a lot of questions from people asking if they are worth it, so I think it is time I created a post from someone who actually has them.

Initial Cost: £7950
Grant: £2500
Remainder to be paid by me: £5450

Units generated in one year: 1186
Units predicted by installers: 1130
Units used by house: 3870
% covered by solar panels: 30%
Amount saved off bill (assuming each unit is 15p): £177.90
Payback assuming everything stays the same: 30.6 years
Warranty on panels: 25 years
Life expectancy (albeit not all covered by warranty): 60 years

With my current setup, my meter spins backwards during daylight (assuming I'm not in the shower, or ironing/hoovering)
However, I have applied for Scottish Powers solar tariff where I get 28p for every unit I export.
This changes the numbers as follows:

Units generated in one year: 1186
% exported: 50% (estimated)
Scottish Power payment: £166.04
Amount saved off bill (for my own use of panels): £88.95
Annual saving: £254.99
Payback assuming everything stays the same: 21.37 years

From April next year, I will qualify for the UK Feed-in-tariff.
This pays 36.5 for every unit I generate (whether I use it or not)
WARNING - not all technologies qualify for the 36.5p - don't assume that if you generate electricity by another method, you get such a high payment

Units generated in one year: 1186
Feed-in-tariff: £432.89
Amount saved off bill (assuming each unit is 15p): £177.90
(You'll still be saving any electricity off your bill as in the first estimates)
Annual saving: £610.79
Payback assuming everything stays the same: 8.92 years

People often ask about maintenance on PV solar..
It is nil, absolutely nil.
Bird poo goes on, bird poo washed off by rain.
They get dusty, they get clean in the rain again.
I've not attempted to clean them, but if I really wanted to, a hosepipe would easily be able to get them from the ground.
I hope this answers any financial related questions regarding my solar PV panels, but if you have any more, please send them through.

Cardew

daytona600 wrote: »

8 x 180Wp panels gives total of 1.44kw
but at £ 7950 your supplier is wearing a mask
i supply 1.44kw system for £ 4999 less grants

for complete ready to install system
pv panels , inverters , roof mounting system all installation equipment

certified to MCS - microgenerationcertification for low carbon buildings
grants £ 1000 to £ 2500 - £4000 in scotland , more for charities 50% +
grants would cover installation
8 x 180wp pv panels is only £ 2448
26 x 180wp pv panels is only £ 7995 4.68kw

your payback time would be vastly reduced
for £ 7950 would supply complete 2.8kw system with 16 x 180w panels

if you need any more information on how your roof is the best investment
spend £10.000 on pv system will generate £30.000 in next 25 years

scott

5 posts all from some solar salesman it would appear.?