How do your 12 month generation figures from PV compare to estimated?

GaryMo_2

Just wondering if anybody has passed the 12 month mark with their PV system and if so how their generated figures compare to those that were given to them with their quotation, for example SAP or PV*SOL estimates.

Also how do they compare to estimates from sites such as PVGIS ?

The_Green_Hornet

GaryMo wrote: »

Just wondering if anybody has passed the 12 month mark with their PV system and if so how their generated figures compare to those that were given to them with their quotation, for example SAP or PV*SOL estimates.

Also how do they compare to estimates from sites such as PVGIS ?

My first full year's generation was 33.1% above installer quotation and 5.6% above Climate-SAF PVGIS estimation.

The last twelve month's generation is 38.5% above installer quotation and 9.9% above Climate-SAF PVGIS estimation.

GaryMo_2

That's great news, bet you were over the moon with that!
Hope mine can give similar over performance figures.

don0301

GaryMo wrote: »

That's great news, bet you were over the moon with that!
Hope mine can give similar over performance figures.

From what I've seen, most people without shading problems, are seeing similar outcomes. I've yet to see anyone getting significantly low readings, unless they were stupid enough to get a system not suitable.

larkim

Perhaps that's mainly a result of the weather being a little bit sunnier than the average? I think you'd need many more years to give a statistically valid "average" amount of sun than just one.

I'm no mathematician (despite accountancy ) so I imagine someone will be able to tell me how many years would be needed for a valid sample.

Matt

EricMears

larkim wrote: »

I'm no mathematician (despite accountancy ) so I imagine someone will be able to tell me how many years would be needed for a valid sample.

I believe the PVGIS figures are based on results over the last 30 years - in which case it would take an average based over at least six years (more than the squre root of 30) to have any statistical significance and more than 15 (half original dataset) to be reliable.

If however you're a 'Global Warming Believer' you're not going to expect that the next 30 years will be reliably forecast by the last 30 years.

Martyn1981

EricMears wrote: »

I believe the PVGIS figures are based on results over the last 30 years - in which case it would take an average based over at least six years (more than the squre root of 30) to have any statistical significance and more than 15 (half original dataset) to be reliable.

If however you're a 'Global Warming Believer' you're not going to expect that the next 30 years will be reliably forecast by the last 30 years.

Leap of faith here then, but if PVGIS is based on last 30 years, and the Met office sunshine levels are based on the 30 years from 1971 to 2000. Then ..... let me think about this ....

combining the 2 by comparing monthly sunshine +/- against PVGIS estimates shouldn't be too far off to see if you did realistically, or got a bonus (penalty) from sunshine levels.

I think?

Lots of assumptions going on here I know, I guess I should just be happy that they are doing well.

Mart.

celerity

We have a south facing 3.91kWp system in Cambridgeshire, installed April 2011. We met our PVGIS estimation by Jan 1st 2012. As of today we are 15% above our 1st year target, but of course still have over a month to go.

In monetary terms this will be well over £1,800 from the FiT and export, plus my personal estimation of around £200 saved in electricity (I work from home a lot, a normal household probably wouldn't save as much as this).

So, around £2K for year one, which is way beyond what I'd hoped.

Note I differ from some on here that calculate their system will pay for itself in 6-7 years. I'm not going to get too excited about one year of good results, and I factor in the loss of compounded interest of the initial £1x,000 investment. I'm therefore hopeful I'll achieve what I class as payback within 11-12 years.

Hope that helps,

/\

GordonGowk

4kW system in Scottish Borders - 10% above yearly estimate with 2.5 weeks to go.