Renewables: "talking 'bout my generation"

1echidna

Martyn1981 wrote: »

Evening. Depends what they put in writing in the quote, and what the figure is on your MCS cert.

This time of year can be a bit disheartening, as the sun sets lower and lower, and begins to miss out more and more E + W. Ho hum! Still, the steep roofed Southers will be having fun!

Still it's a bit of fun, and it'll be March again before you know it.

Grey all day here, got East 2 and West 1.3. Looks like another 4 days of solid grey, then some nice days.

Mart.

Thanks Martyn, indeed yes, a bit of fun and I can't get too worked up over it but there is the principle of the thing.

MCS Certificate quotes Estimated Annual Generation at 3623kWh but it was sold on the basis of 870 x 3.992 x 90% = 3124kWh. The salesman went on about how this was a conservative figure and how we would get a discount by allowing them readings of our generation so the could use them to get authority to increase their quotes in future.

The salesman also mentioned that the latest inverters allowed them to discount a panel if it was in the shade. Now we do have a degree of shading to one or two panels at this time of year but as far as I can tell the wiring is in two strings, one for each side of the roof. I'm no electronic expert but does this allow the affected panel(s) to be switched out? If that is the right terminology?

The other thing that annoys me in retrospect is that the costings quoted assumed we could use all the power generated. I guess I suspected that this wouldn't be the case, especially as we have a combi gas boiler and no immersion heater but they must have known that for the average household even 60% recovery may be pushing it.

Allowing for some degradation of the panels on the figures they quoted we would have had a payback of about 14 years. In practice I think at the end of 14 years we will be £2k+ short and at the moment I feel justified in pushing for that. Any thoughts?

Oscargrouch

1echidna wrote: »

Thanks Martyn, indeed yes, a bit of fun and I can't get too worked up over it but there is the principle of the thing
MCS Certificate quotes Estimated Annual Generation at 3623kWh but it was sold on the basis of 870 x 3.992 x 90% = 3124kWh.

Shouldn't fret too much, too soon, you are at the Donkey's Tail of the year at present. No doubt next May & June, your system will be booming!!

1echidna

Oscargrouch wrote: »

Shouldn't fret too much, too soon, you are at the Donkey's Tail of the year at present. No doubt next May & June, your system will be booming!!

Thanks for the encouragement

shafeeq

Oscargrouch wrote: »

Think I may have a record for today, even Shafeeq will better it, a total of 2.4 kWh, may be time to ask for a discount.:rotfl:

Man your psyche 5.27kwh... what happened with your system?


Shafeeq

Martyn1981

1echidna wrote: »

Thanks Martyn, indeed yes, a bit of fun and I can't get too worked up over it but there is the principle of the thing.

Nothing wrong with principles, especially if you think it's worth a go.

1echidna wrote: »

MCS Certificate quotes Estimated Annual Generation at 3623kWh but it was sold on the basis of 870 x 3.992 x 90% = 3124kWh. The salesman went on about how this was a conservative figure and how we would get a discount by allowing them readings of our generation so the could use them to get authority to increase their quotes in future.

Here's a link to SAP calcs:-

http://www.spssolar.co.uk/ReturnOnInvestment/SAPCalculation.asp

If I'm doing yours correctly, it should be 3.992(kWp) * 0.8(UK) * 913(E/W @ 30deg) * 0.8 or 1 (shading) = 2,916 (ish).

But forget SAP, unless you live in Sheffield, and have a good play with PVGIS.

I'm surprised at the MCS cert, as 3,600 is a pretty good figure for a South system. So it'll depend where you are, possibly somewhere between the two. But back to PVGIS I'm afraid - it's really good!

1echidna wrote: »

The salesman also mentioned that the latest inverters allowed them to discount a panel if it was in the shade. Now we do have a degree of shading to one or two panels at this time of year but as far as I can tell the wiring is in two strings, one for each side of the roof. I'm no electronic expert but does this allow the affected panel(s) to be switched out? If that is the right terminology?

I didn't want to worry you, but that was why I asked what inverter you had, when I saw you had a split system. There have been quite a few people looking for help and advice this year due to split systems (combining differing roof orientations, or roof pitches, or unbalanced multi strings). But your inverter has dual MPPT, so will act like two inverters, getting the most out of each roof, without the shaded one, dragging the unshaded down with it. So good choice of inverter.

As to individual panels - unfortunately if a single panel in a string is in enough shade, then that panel can drag the whole string down by say 50%. Not a lot you can do about that, and many of us will have shading issues at certain times of the day, or year, as the sun gets ever lower.

1echidna wrote: »

The other thing that annoys me in retrospect is that the costings quoted assumed we could use all the power generated. I guess I suspected that this wouldn't be the case, especially as we have a combi gas boiler and no immersion heater but they must have known that for the average household even 60% recovery may be pushing it.

Allowing for some degradation of the panels on the figures they quoted we would have had a payback of about 14 years. In practice I think at the end of 14 years we will be £2k+ short and at the moment I feel justified in pushing for that. Any thoughts?

For consumption, I reckon an average household will use around 30% to 40%. 50% will require some effort, (or a clever immersion device). You really won't know for sure, till you suck it and see, but I'd guess at £100 (£70 to £150) savings but hope and aim for more. Obviously high daytime consumption will give the greatest savings.

Payback's a *****. Couldn't resist the quote. Hard to say, depends on a lot on inflation and fuel price inflation. Also if you value education, pure entertainment value, doing your bit for AGW etc etc. Plus chatting on here, keeps me out of the parks drinking meths, so that's a plus for some (and a negative for others!).

Are you still smiling? I'm off for some Family Guy.

Mart.

1echidna

Thanks Martyn, what you say about the inverter is comforting. My talk about the payback was just a bit of a device to try to pin some figures on them for what seems to me to be a misleading sales pitch. I'm still smiling but would welcome any comments anybody else has.

John_Pierpoint

3.48 kWh, actually better than the 01oct12 when another wet day gave 2.86; so still looking for the next winter low to match the 1.98 on foggy 02mar12..

John_Pierpoint

1echidna wrote: »

Thanks Martyn, what you say about the inverter is comforting. My talk about the payback was just a bit of a device to try to pin some figures on them for what seems to me to be a misleading sales pitch. I'm still smiling but would welcome any comments anybody else has.

What is causing the shadows?

Martyn1981

1echidna wrote: »

Thanks Martyn, what you say about the inverter is comforting. My talk about the payback was just a bit of a device to try to pin some figures on them for what seems to me to be a misleading sales pitch. I'm still smiling but would welcome any comments anybody else has.

Morning, I think you have an argument, but will depend on what they quoted and what you'll get.

I've knocked a simple spreadsheet together, easy to re-produce:-

First section is cost of install, plus ISA interest, rinse and repeat (R&R).

Section 2 is the estimated annual income from the PV (FITs + Export + savings). Then year 2 increase by inflation guess, perhaps 3% and a panel degradation factor (I multiply by 0.995). R&R.

Section 3 is important, here I take the annual income from section 2 and compound it (like section 1). R&R. You can also deduct an amount for a new inverter in here somewhere, maybe knock off £1k every 12 years or so?

Happy to insert some guesses for you, but would need an accurate estimate of annual generation as a starting point. If it's not too stalkeresque you could PM your PVGIS results, or the first half of your postcode would also do.

As to your chances of success, I expect it'll depend entirely on the way the quotes are worded, but best of luck.

Mart.

1echidna

John_Pierpoint wrote: »

What is causing the shadows?

It is a medium sized tall thin conifer, on our property but would wish to take neighbours views into account if we considered removing.