Solar Panel Guide Discussion

K4blades

zeupater wrote: »

Hi

I thought that that would be eminently apparent ..... with such a fervour for solar pv you obviously have a system, as do many others who post on this forum, therefore it would be logical to assume that having such strong views on the likely level of electricity savings would be based on your own experience with a system, so again, how is your system performing ? If it's performing well relative to others, can you share details of the measures which you are taking in order to maximise self consumption.

HTH
Z

You only had to ask........

1) I don't have a "fervour" for solar PV specifically, in the way you think. I believe in having as many eggs in the basket as possible, so you can cover as many bases as possible.....he says mixing his metaphors, but I hope you get my point.

2) The reason I have been a bit reluctant to offer figures in the past is because, time and time again, other people have, only to have certain members constantly call into question those numbers, suggesting the the original contributor is wrong / lying / stupid, etc. I have had pms from several people expressing this view, and I think it is detrimental to the whole debate.

But as you ask.....These are the facts and I will not try to prove them, I don't need too, if anyone wants to question them, I have no reason to lie, so its up to the reader to decide if its true or not.

I have a standard ASG system, 3.3 kw peak, almost bang on south, about 40 degrees pitch, no shading, in South Yorkshire. Had I got the money, I would have bought my own, but that is not an option for us in the foreseeable future.

I haven't had them up a full 12 months yet, but as we are pretty much mid-point for this year, I will give the results for those 6 months.

Total generated, (Jan 1st to today) = 1711kwhs.
I appreciate we have had a good spring, so we won't get this every year, but over 25 years, there will be some good years, and some bad, averaging out over 25 years.

Based on that, we would generate 3422kwhs for the 12 months of this year, but obviously, the second half won't be as good. If we finish with over 3000 I consider that a good result for our size system, and above what ASG expect.

Our worse day was when we generated 1kwh, only once, and our best so far is 24.

Usage.
In the first 6 months of 2010, when we didn't have PVs, our consumption was 2959kwhs, taken from monthly readings of our import meter.
Since having the panels fitted, I take daily readings which I use for my own research.
Our import meter shows that in the first 6 months of 2011 we have used 1720kwhs.
This is a reduction of 42%

I don't really consider anything in £s as tariffs, etc change, so only look at the units used. But if you take the average commonly used of 10p, 2959 - 1720 = 1239 x10p = £123 for 6 months.

As I said before, we have had a good spring so wouldn't expect that sort of saving every 6 months.

Of course, not all of that saving is as a direct result of the PVs, one of the things I'm interested in is how peoples behaviour changes, which adds to the saving, so its more indirect. Clearly, as seen on this forum, when people have a system on their roof, they do change the way they behave. This could be used as an argument for domestic installations compared to industrial where people just take the grid for granted. In my opinion, one thing we all want, is for demand to fall through more efficient use of electricity. In my experience, most people only want to know how much they will save, whether thats direct or indirect from PV is less of a concern.

As for us, using our system:
I work from home, but am constantly in and out, so hard to commit to specific tasks at home, and being a Yorkshire man, don't know how the iron works.
We have 2 small children meaning we have a large laundry demand, washer, iron, and sometimes, dryer, but my wife works funny shifts so though we start with good intention in terms of appliance usage, they sometimes go out of the window. However, we are confident that if we were to really try, (and kick the kids out ha ha ), we could achieve a 50% reduction compared to pre PV.

That is in terms of kwhs as I mention, so as prices increase, we would expect that to represent a larger amount in absolute terms.

At some point in the future, we are considering using an electric car, (not because we have PVs but because it makes sense for us in other ways, if the costs come down), so hopefully, our overall house-hold expenditure could benefit there too and allow us to use up more of the generated power that is currently exported.



I think thats everything, if you want to know more, just ask...but I'm not on the witness box, so don't treat me like an hostile witness.

grahamc2003

John_Pierpoint wrote: »

int rate on cash 5%
inflation rate 4%

Plus or minus 80% accuracy ?
We just don't know.

Obviously we don't know - that's exactly why scenarios are used. You either use reasonable values in scenarios, or you simply have nothing to go on, so doing such an analysis is (much) better than doing nothing and having no idea whatsoever of the possible paybacks, or even their order of magnitude.

Would you like me to feed in different parameters to see how the numbers come out? Higher/lower inflation, higher lower interest rates, higher.lower intital year return from solar?, or higher/lower sola spend/investment? Don't you find looking at the effects of such changes interesting (well, a little bit interesting?)

John_Pierpoint

I did a similar exercise some months ago with a higher inflation rate and a lower interest rate.
I also assumed that the inflation in charges for power would be double that of "normal" inflation - partly because of all the "green" measures I would be forced to finance.

I'm currently listening to rubbish about so called civil servant and teacher salaries.

Does anyone believe those wonderful figures for economic growth?

More like going nowhere per head in real terms and enjoying a halving of the currency value.

But what do I know I'm on the pensioner's inflation rate.

celerity

grahamc2003 wrote: »

Initial spend/investment - £15k
int rate on cash 5%
inflation rate 4%
1st year fit + used electrcity value £1300

Did you remember to reduce the output each year by 0.8% to take into account panel degradation?

Your figures seem a little pessimistic to me.
I would use an initial outlay of £13K now, as I think that is closer to the going rate for an (approx) 4kWp install.
My estimated year 1 FiT + export earnings are £1,500 - it remains to be seen if we will hit that of course - May and June see us 30% above but obviously this could change very easily in the next ten months.
For interest, inflation rates (for FiT increases) and electricity rises I kept everything to 3% for the whole period - this was just a guess though and is probably way out.

My bill savings are estimated at £200 for the first year, but as discussed in other threads, I have unusual usage due to working at home, and I still might be being optimistic.

I'm actually not interested in the total profit I expect to see - what interests me is how quickly I will reach a break-even point had I invested the capital at the start. By my figures this is during year 12.

If you could plug the above figures into your spreadsheet and tell me the payback period that would be appreciated.

/\dam

Bingobongo

Die Welt has a piece today headlined "The great solar swindle".
Unfortunately I am not allowed to post links on this thread.
Type the title into google and follow the link on the first result which comes from notrickszone.
Enlightening.

keith_r59

Bingobongo wrote: »

Die Welt has a piece today headlined "The great solar swindle".
Unfortunately I am not allowed to post links on this thread.
Type the title into google and follow the link on the first result which comes from notrickszone.
Enlightening.

I've posted the link for you.

http://notrickszone.com/2011/06/29/the-great-solar-swindle/

zeupater

K4blades wrote: »

You only had to ask........

Hi

Thanks for the reply. Looking at the figures it seems that you have a large atypical baseload, with a six-monthly consumption close to the national average for a whole year. The level of usage would also suggest that electricity is not the main form of heating (?). Using over 70% of total annual generation already within the house wouldn't leave much scope for being able to charge a vehicle, with the unused ~1000kWh being almost certainly being limited to summer that would only provide around 5kWh/day, even if you could control the charge to match the pv production ..... maybe that would be the time to look at 'off peak' electricity if the car is to ever expected to leave the drive

As a direct comparison, my household consumption was gradually reduced from circa 4500-5000kWh.y, which already included a number of energy saving features, to ~2800kWh.y in the five years leading up to installing pv, and has been reduced by a further ~200kWh.y since. Most of the energy savings resulting from pure common sense changes aided towards the end by using energy monitors .... my strong belief is that taking this approach will save anyone more than 'r-a-r' pv ever would. Only once the energy consumption was minimised was a grid tied pv system considered, although I have had a small 'off grid' system for a number of years. The main advantage of having addressed & reduced energy consumption behavoir prior to installing pv is that any further savings can only be related to the installation.

Additional savings have also been made in the energy required for heating .... gas usage has reduced from a rolling 12 month total of ~25000kWh five years ago (used to be 34000kWh+ before that !) to a rolling 12 month figure of just over 7000kWh now ...... some of this is attributable to a HE condensing boiler, but that wasn't even looked at until we'd insulated until it hurt, then insulated some more !!, the result being a property which now far exceeds the energy performance of almost all new builds .....

HTH
Z

jpmcc

digitaltoast wrote: »

Ehhhhhhhh? I can't make any of that work out. Where are the calculations for initial investment, replacement costs, inflation etc?

Plugging your figures into the EST calculator I get a "lifetime income" of £38,828-£12000 = £26828, with the breakeven point at year 8 (excluding all maintenance). Are you sure you've taken into account the loss of investment from years 1 to 8? What am I missing here?

As far as I can see, the EST calculator looks at simple cash flows. It assumes you put all the money under your mattress. My calculations use the 4% ISA assumed in the original posting.

John

grahamc2003

celerity wrote: »

Did you remember to reduce the output each year by 0.8% to take into account panel degradation?

Your figures seem a little pessimistic to me.
I would use an initial outlay of £13K now, as I think that is closer to the going rate for an (approx) 4kWp install.
My estimated year 1 FiT + export earnings are £1,500 - it remains to be seen if we will hit that of course - May and June see us 30% above but obviously this could change very easily in the next ten months.
For interest, inflation rates (for FiT increases) and electricity rises I kept everything to 3% for the whole period - this was just a guess though and is probably way out.

My bill savings are estimated at £200 for the first year, but as discussed in other threads, I have unusual usage due to working at home, and I still might be being optimistic.

I'm actually not interested in the total profit I expect to see - what interests me is how quickly I will reach a break-even point had I invested the capital at the start. By my figures this is during year 12.

If you could plug the above figures into your spreadsheet and tell me the payback period that would be appreciated.

/\dam

I hadn't forgotten about panel degredation, just decided for simplicity to ignore it for the time being, plus I didn't know an annual degredation figure. I'll stick it in later to see it's effect.

In answer to John's point, Although I expect bills to rise higher than inflation, the effect on projections will be relatively minor, since the starting point would only be £70 in year 1.

But for

int rate 3%pa
inflation 3%pa
Investment/solar cost £13k
1st year fit+elec saving £1500
2 inverters at yr 10 and 20

means the isa grows to £27.2k
solar returns are £53.1k
and 13k initial cost generated from fits in year 8

silvasands

Just like initially, to make a comment in reply to the person who was annoyed about middle classes buying solar panels and being subsidised or whatever. I`m working class...as I work for a living.( As my socilaist father used to say...anyone who works, is !)I saved for ages ready for retirement and had sufficient saved to buy them this year. It`s also my own way of helping reduce my c footprint. I have never had a new car and paid to have my car converted to lpg.
Re the panels, they are working very well . Max they have produced in a day is around 21kw.We are not south facing but have a gently sloping roof to our bungalow.
We are with Swalec and had a problem getting them to actually backdate the feed in tariff. The microgeneration team weren`t helpful when my husband rang up and didn`t tell him some necessary facts to ease the feed in process. However, another dept. of Swalec listened to our complaint and rectified the problem.They were excellent! The microgeneration team need to get their act together.
I heard that a whole village in Germany has opted for solar panels some while ago. We used to be innovative in The UK ...we are tending to lag behind, presently. We are free to choose. I don`t need to be lectured on how to spend money I have saved...thanks!
If you have the savings...my advice is that they are worth it. It`s a great feeling, generating your own power.:cool: