Solar: how much you paid (£) how much you have generated (kWh) and date of install.

Martyn1981

cepheus wrote: »

As far as I can tell, a brand new clean domestic PV system at todays prices can produce around 15p/kwh, compared to around half that for large scale on-shore wind farms.

As it's been a couple of days, can I ask again for you to post your calculations. No need to spend lots of time on this, just quickly type up the calculations you used to get to 15p, since you must have them to hand.

I tried to recreate 15p but had to go to extremes:

£8k install, 25yr mtg at 4% with generation of 3,500kWh, or

£7k install, 25yr mtg at 4% with generation of 3,200kWh, or

£8k install, 25yr self financed at 2% with generation of 3,000kWh.

cepheus wrote: »

However, it's going to be impossible to determine how well these systems work in practice by examining any new system and just those which people wish to report which are surely the most favourable.

But this started off with you making 'statements of fact', and my asking you to support those statements. I hardly think that you can use the excuse that - "you can't support your own statements, because months later, other people haven't given you the information you want." That would suggest you simply made it up?

Or, you could do what I've suggested numerous times, and use real current prices that are at the better end, but not extreme examples, as reported on these threads - £5k. And use real generation potential from PVGIS at the better end, but not extreme examples of 1,000kWh/kWp.

cepheus wrote: »

5 p/kWh is the commercial price target, which would be easily achievable in the most windy locations such as the islands off Scotland, but once again these are the most favourable, so perhaps these need to be used for cost comparisons.

Nope. You should not use an extreme example, just a good example. Also, picking examples that will require a large amount of infrastructure spend, kind of misses the point. It's akin to putting all the PV in Cornwall, and ignoring the enormous cost of HVDC interconnectors to 'ship' it around the UK.


Anyway, back to my first question, if you could just pop down the 15p calcs you used, which must be fresh in your mind, that would be appreciated. As you've probably worked out already, I'm particularly interested in the sheer level of negative spin that you are willing to go to.

Mart.

EricMears

Martyn1981 wrote: »

As it's been a couple of days, can I ask again for you to post your calculations. No need to spend lots of time on this, just quickly type up the calculations you used to get to 15p, since you must have them to hand.

I'd be amazed if you get your reply !
I've just done a simple calc from first principles :-

£5000 would be a fair price for a 4kWp SP system these days
£500 is a generous provision for a new inverter around year 10
Total (20 year) lifetime system cost would therefore be £5500
4500 kWh is what you'd expect a 45deg S facing roof in Sheffield (the FIT scheme's typical example) in an average year
20 years @ 4500kWh pa gives 90,000 kWh
That gives a 'raw' cost of 6.11 pence per unit (ignoring any FIT income)

You could increase the total lifetime cost by borrowing the initial £5k - but that would be a different case entirely. To get unit price up to 15ppu you'd have to include interest payments of more than 5% but completely ignore any benefits from the electricity you hadn't had to buy (let alone the FIT payments).
You could reduce the 90MWh output by choosing a shady site or switching it off at weekends. Either would be silly.

zeupater

EricMears wrote: »

I'd be amazed if you get your reply !
I've just done a simple calc from first principles :-

£5000 would be a fair price for a 4kWp SP system these days
£500 is a generous provision for a new inverter around year 10
Total (20 year) lifetime system cost would therefore be £5500
4500 kWh is what you'd expect a 45deg S facing roof in Sheffield (the FIT scheme's typical example) in an average year
20 years @ 4500kWh pa gives 90,000 kWh
That gives a 'raw' cost of 6.11 pence per unit (ignoring any FIT income)

You could increase the total lifetime cost by borrowing the initial £5k - but that would be a different case entirely. To get unit price up to 15ppu you'd have to include interest payments of more than 5% but completely ignore any benefits from the electricity you hadn't had to buy (let alone the FIT payments).
You could reduce the 90MWh output by choosing a shady site or switching it off at weekends. Either would be silly.

Hi Eric

Maybe 4500kWh/year in Sheffield is a little over-optimistic for a 4kWp system (12.34kWh/day) ?? ..... did you mean 3500kWh ?? .... here's a random selection of systems around Sheffield ( http://pvoutput.org/listmap.jsp?o=e&d=desc&id=8726&sid=7091 )

PVOutput currently calculates an average for the UK of 2.383kWh/kWp/day which would suggest 3480kWh annually for an average 4kWp system, with an average orientation, an average roof angle, average efficiencies and average insolation over the past few years - so why not just use that ?? .... ( http://pvoutput.org/country.jsp ).

Although higher figures may be possible, I'd find it much harder to accept or justify anything over 900kWh/kWp as being a standardised figure to use for an average system with a decent orientation and no shade upon which generalisations are to be based ...

HTH
Z

Martyn1981

zeupater wrote: »

Hi Eric

Maybe 4500kWh/year in Sheffield is a little over-optimistic for a 4kWp system (12.34kWh/day) ?? ..... did you mean 3500kWh ?? .... here's a random selection of systems around Sheffield ( http://pvoutput.org/listmap.jsp?o=e&d=desc&id=8726&sid=7091 )

PVOutput currently calculates an average for the UK of 2.383kWh/kWp/day which would suggest 3480kWh annually for an average 4kWp system, with an average orientation, an average roof angle, average efficiencies and average insolation over the past few years - so why not just use that ?? .... ( http://pvoutput.org/country.jsp ).

Although higher figures may be possible, I'd find it much harder to accept or justify anything over 900kWh/kWp as being a standardised figure to use for an average system with a decent orientation and no shade upon which generalisations are to be based ...

HTH
Z

I think you've been fair and accurate to find an average system.

However, in my calculations, as explained, I've aimed for the better end, without going to the max. The idea being to see what is possible today, if we want to find the 'first' systems to go subsidy free (or very low subsidy, such as 3p/kWh). Or just to compare p/kWh.

Looking at PVGIS and changing the default losses to 10% (from 14%) since everyone(?) seems to be beating them, that would seem to give an average of 1,000kWh/kWp when comparing locations south of Sheffield (950 to 1050). If we go a little further down, to say Birmingham, then most locations (but not quite all) are close to or higher than 1000.

I appreciate that this isn't a true average for average PV, but my thinking is to find the better locations, then the poorer locations would follow in the next decade or so, as panel prices fall, and efficiencies sneak up. If efficiencies do rise by ~10% over the next decade (from say 15% to 16.5%), then that would lift the 900kWh/kWp locations into the same price potential of the 1,000kWh/kWp locations, through greater potential kWp capacity.

I hope you see what I mean, and what I'm trying to do, as it's not that easy to put it into words.

Also, there are quite a few other PV technologies being developed, (and good ole high efficiencies too, which could raise the potential of any given roof area as their prices drop). Or simply bring the cost down further.

I don't think I'm being at all unreasonable to suggest that the p/kWh is only going to go down for a while yet.

Mart.

Martyn1981

zeupater wrote: »

PVOutput currently calculates an average for the UK of 2.383kWh/kWp/day which would suggest 3480kWh annually for an average 4kWp system, with an average orientation, an average roof angle, average efficiencies and average insolation over the past few years - so why not just use that ??

HTH
Z

Out of interest, I slapped 3,480* into one of my spreadsheets and got 8.46p/kWh, which I didn't think was too bad.

This was using the repayment mtg model, over 25yrs, on a cost of £5k plus £1k added at month 145 for an inverter. But I used an interest rate of 2% to reflect own capital used. The idea being that the mtg model reflects the use of capital, and cost of capital, so no need to worry about depreciation or claims that the opportunity cost of the funds has been ignored.

Probably not the best way to find a year one cost, but I think it works for simple ponderings.

* @4,000kWh it works out to 7.36p/kWh.

Mart.

EricMears

zeupater wrote: »

Hi Eric

Maybe 4500kWh/year in Sheffield is a little over-optimistic for a 4kWp system (12.34kWh/day) ?? ..... did you mean 3500kWh ?? .... here's a random selection of systems around Sheffield

Indeed yes. I'm sure keyboard keys are getting closer together !

That of course increases my 6.11ppu to 7.85 (but still not to 15p)

zeupater

Martyn1981 wrote: »

Out of interest, I slapped 3,480* into one of my spreadsheets and got 8.46p/kWh, which I didn't think was too bad .....

Hi

I'd reckon that the normal way to approach something like this would be to work the figures based on average and describe a performance range based on the distribution curve .... of course, you'd need to filter out systems with little history (<2years ?) and obvious anomalies in order to not skew the range .... so something like 875kWh/kWp with a spread of +/-20% to cover location and orientation would probably be reasonable .... therefore the spread you'd be looking for would be - Low(South-Coast/Ideal-Install)=6.77p/Av=8.46p/High(More-Northerly/Not-Ideal-Install)=10.15p, where around 80% of systems fall within ~8% of the average on the distribution curve ...

HTH
Z

jimjames

zeupater wrote: »

Hi Eric


Although higher figures may be possible, I'd find it much harder to accept or justify anything over 900kWh/kWp as being a standardised figure to use for an average system with a decent orientation and no shade upon which generalisations are to be based ...

HTH
Z

We're not in Sheffield (actually SE England) but are getting approx 1100 kWh/kWp from ours which isn't due South although no shade so either we have exceptionally efficient system or over 1000 is easily achievable for the right location and orientation.

zeupater

jimjames wrote: »

We're not in Sheffield (actually SE England) but are getting approx 1100 kWh/kWp from ours which isn't due South although no shade so either we have exceptionally efficient system or over 1000 is easily achievable for the right location and orientation.

Hi Jim

... I agree, but that's the point ... although you're in a good location with an orientation which is likely to match average local weather conditions, others may not be, there are systems reporting 800kWh/kWp and below. If the exercise is to establish a level of support it's more reasonable to establish that figure against average rather than exceptional performance else it becomes a ridiculous exercise .... would we need to compare exceptional pv against exceptional off shore or exceptional coal or exceptional nuclear too, or are the available figures for the rest to be average and the exercise open to criticism for intentionally skewing the results ??

What exactly is the best performing site for each (non-pv) source of generation & what are the costs of running those sites ??

HTH
Z

Martyn1981

zeupater wrote: »

Hi

I'd reckon that the normal way to approach something like this would be to work the figures based on average and describe a performance range based on the distribution curve .... of course, you'd need to filter out systems with little history (<2years ?) and obvious anomalies in order to not skew the range .... so something like 875kWh/kWp with a spread of +/-20% to cover location and orientation would probably be reasonable .... therefore the spread you'd be looking for would be - Low(South-Coast/Ideal-Install)=6.77p/Av=8.46p/High(More-Northerly/Not-Ideal-Install)=10.15p, where around 80% of systems fall within ~8% of the average on the distribution curve ...

HTH
Z

Hiya Z. That sounds fair, and I like the range. The problem with trying to find an average generation though is that it's being skewed (a bit) by FiT fairness!

For supply side generation, the subsidies are lower, and you have to go to a location that works near the better end.

For demand side gen, the subsidies are more generous, since you can't move your house or factory, or change its roof orientation. So, in order to try to be more inclusive, and not discriminate against northerly locations, or non-south orientations the FiT is higher, and that means that installs (such as mine) can work, whilst simultaneously boosting the profits of southish installs.

This subsidy model (and I'm not knocking it for being more inclusive) means that the average gen will be dragged down a little by installs that would otherwise have to wait till technology and price improvements bring them into the fold.

That's why, when taking the argument one step further, I've talked (theoretically) about non-subsidised PV being compulsory on south facing new builds. If that happens, or could happen, then any suggestions that PV isn't economic at our latitude become irrelevant.

I think this is all quite interesting, but still surprised at the pace of change.

Mart.