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

Screwdriva

Last May's record of 720kWh was obliterated by a new all time high of 865kWh for June '24. Pre-system expansion would have likely seen 565kW (June '22), which means the system expansion has delivered a ~53% increase in generation. 

Screwdriva

For those interested in Bifacial panel technology, end user Ian has shared daily generation data from his installation. Side by side performance of the Sharp 425W panels (on roof)  vs. the Sharp 580W panels (flat roof with white painted roof surface). He is seeing an average of 11-13% incremental efficiency, with even greater outperformance (upto 37%) on overcast days.  

https://pvoutput.org/compare.jsp?sid=104850&sid1=104852&t=d

Reed_Richards

Seemed to be a comparison of "flat" with "ridge", not side by side.  

Screwdriva

Reed_Richards said:

Seemed to be a comparison of "flat" with "ridge", not side by side.  

Two different mountings and two different panel types on the same roof aspect. 

Screwdriva

The bifacial system expansion is really coming into its own! A ~75% increase in generation for August '24 (over the average of the last 4 years!). The system has generated more in the first 7 months of 2024 than it did for any prior year in total.

Qyburn

August must have been a good month. We had 933kWh vs PVGIS August estimate of 742. (8.1kWp North East Scotland) 

NedS

@Screwdriva Just reading this thread for the first time.

Just wondering if you are still on your original 3.68kW inverter as per your signature, as you have a 7.3kWp array (plus any uplift from bi-facial panels) and no mention of any battery storage. You must see significant clipping in summer, but equally probably benefit from the additional generation the rest of the year? Just wondering how that all plays out.

Screwdriva

NedS said:

@Screwdriva Just reading this thread for the first time.

Just wondering if you are still on your original 3.68kW inverter as per your signature, as you have a 7.3kWp array (plus any uplift from bi-facial panels) and no mention of any battery storage. You must see significant clipping in summer, but equally probably benefit from the additional generation the rest of the year? Just wondering how that all plays out.

Yes, still on the original 3.68kW SolarEdge inverter on our triple aspect system. And yes, we do experience clipping in June/ July but not as much in May/ August.  No battery due to a low annual import of < 1600 kWh. 

The diagram below summarizes the result of the system expansion nicely. Raising the overall generation curve has dramatically improved generation for relatively low additional investment. 

NedS

Screwdriva said:

NedS said:

@Screwdriva Just reading this thread for the first time.

Just wondering if you are still on your original 3.68kW inverter as per your signature, as you have a 7.3kWp array (plus any uplift from bi-facial panels) and no mention of any battery storage. You must see significant clipping in summer, but equally probably benefit from the additional generation the rest of the year? Just wondering how that all plays out.

Yes, still on the original 3.68kW SolarEdge inverter on our triple aspect system. And yes, we do experience clipping in June/ July but not as much in May/ August.  No battery due to a low annual import of < 1600 kWh. 

The diagram below summarizes the result of the system expansion nicely. Raising the overall generation curve has dramatically improved generation for relatively low additional investment. 

Have you considered a larger inverter. Maybe you have and the DNO is restricting you, or maybe you've done the sums and the payback versus what you are losing to clipping does not make an inverter upgrade financially prudent? I'd be interested to see some cost analysis although appreciate that's not necessarily an easy thing to do.

Screwdriva

I have but estimated the annual earnings difference between a 5kW inverter and my 3.68kW to be < £40. (~3kWh per day X 18p per kWh X 60 days per year).