7.3 kW Bi Facial Rooftop Panels: ~7 year ROI: Fact OR fiction?

Screwdriva

Panels are up and running! Reflective paint clearly visible.

We "turned it on" @ 3pm (sunset at 3:51pm) and were at around 405W.

Any suggestions on an energy purchaser? Should I go Octopus or Bulb? Now or after SEG rates are published?

Screwdriva

Another view of the installation. Today's generation here. Panel level generation breakout here.

Generated 3.71 kWh today. What's interesting is that the right side panels don't appear to be generating as much as the left, despite having Solar Edge Optimizers and no significant shading. Any thoughts on the cause? How is the system doing for SE London?

Please weigh in!

Coastalwatch

Hi Screwdriva interesting setup you have there, especialy with the bi-facial panels. It would seem you have panels on three separate rooves so there is likely to be shading to some degree on all of them with the sun so low at this time of year.

I'm a little confused as generation today is stated at 3.71 kWh whereas on the generation breakout pic the total is 1.51 but does clearly show higher outputs on the two west and the two lower panels on the west side of the south facing roof. If this is a snapshot taken half way through the day then with the sun rising in the east you'd certainly espect the reverse to be the case.

Screwdriva wrote: »

Another view of the installation. Today's generation here. Panel level generation breakout here.

Generated 3.71 kWh today. What's interesting is that the right side panels don't appear to be generating as much as the left, despite having Solar Edge Optimizers and no significant shading. Any thoughts on the cause? How is the system doing for SE London?

Please weigh in!

Screwdriva

Yes, the panel level breakup was taken just after 12pm today. The image of the installation above was taken at the same time, so you can see some shade.

Total generation was 3.7+ kW, taken this evening. How did the system do?

ABrass

If it was overcast in one half of the day then that'd make sense. Assuming that's a more or less south facing roof then the left panels would be shaded by the chimney in the morning and the right in the afternoon. So if it was a gloomy morning and a brighter afternoon then you'd see different results for the east and west sides.

EricMears

Screwdriva wrote: »

Another view of the installation. Today's generation here. Panel level generation breakout here.

Generated 3.71 kWh today. What's interesting is that the right side panels don't appear to be generating as much as the left, despite having Solar Edge Optimizers and no significant shading. Any thoughts on the cause? How is the system doing for SE London?

Please weigh in!

Sorry, but with panels on 3 sides of a tall chimney there will be 'significant shading'.Whether the left or right panels are 'doing better' will be a function of whether the morning or afternoon was sunnier than the other.

Exiled_Tyke

EricMears wrote: »

Sorry, but with panels on 3 sides of a tall chimney there will be 'significant shading'.Whether the left or right panels are 'doing better' will be a function of whether the morning or afternoon was sunnier than the other.

Yep. Agreed. This time of year is terrible for generation. Where I am the sun only rises to about 13 degrees above the horizon at this time of year compared to nearly 60 in summer.

So the shading effect is huge. I remember somebody on these boards mentioning that at this time of year PVers suddenly discover the effect of trees in the distance which they hadn't noticed existing before!

Generation for me averages around 1 kWh each day whereas the best months of the year can be easily over 15 kWh.

Like you my install was December and the first few months were quite frustrating as the system does so little.

Martyn1981

Exiled_Tyke wrote: »

So the shading effect is huge. I remember somebody on these boards mentioning that at this time of year PVers suddenly discover the effect of trees in the distance which they hadn't noticed existing before!

At this time of year my ESE system benefits from me mowing the back lawn.

Coastalwatch

Screwdriva wrote: »

Yes, the panel level breakup was taken just after 12pm today. The image of the installation above was taken at the same time, so you can see some shade.

Total generation was 3.7+ kW, taken this evening. How did the system do?

Compared to mine, very well. Afraid we're perhaps 50 miles apart so weather patterns are likely to vary dramatically. Your generation of 3.7 kW averages out at 370 Watts per panel for the day. On the same day our panels averaged 188 Watts!


Edit. Our panels are rated at 295W by the way!

Screwdriva

Many thanks! I’m trying to determine if the system is outperforming other comparably located setups, which would (in my mind atleast), justify the premium.

South/ South West facing panels are far outperforming their siblings.