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

Screwdriva

Consumption:
A. Smart Meter reading on 1st Jan: 7450 kWh
B. Est. Smart Meter reading on 1st Nov: 8810 kWh
Total consumption over 10 months is (B-A): 1360 kWh
Avg. Cost per kWh is ~13.9p (and rising!)
Generation:
A. Total generated as of 1st November is 3820 kWh (via Solar Edge)
B. Est. total exported to the grid as of 1st November is 2965 kWh (via Smart Meter)
Total renewable energy consumed would be (A-B): 855 kWh
Bulb's Payment per kWh is ~5.3p
Amount saved = £120
Amount earned = £155
Total = £275. Pretty bleak outlook on recovery of investment without a substantial increase in electricity and SEG tariffs. 

joefizz

Screwdriva said:

 Pretty bleak outlook on recovery of investment without a substantial increase in electricity and SEG tariffs.

You wont be saying that when they have to inflate the current debt away... Already some utilities have ditched official govt rpi etc and just attached fixed price increases.
Politically raising electricity prices is a hot potato... until its not.
Watch inflation over the next couple of years, it should start to kick in at some point officially next year. In the meantime it just means less money you have to find per month/quarter etc.

Screwdriva

Massive generation drop off from September. Here's hoping we hit 4MW this year, a number previously taken for granted. 

pinnks

October was the second worst October on record for me, so I wouldn't worry too much about that.  Looking at 2020 as a whole it is set to be the best year on record too.  Currently only 80kWh off the previous record year and on average my system should generate 290kWh in Nov/Dec.

Screwdriva

Interestingly, our renewable energy consumption is just over 38% of total consumption, which is higher than I would have thought. 

Screwdriva

And that's a wrap to 2020 with very nearly 4MWh from the bi-facial system.

https://imgur.com/a/zH5TbbZ

Screwdriva

Annual Analysis below:
Consumption:
A. Smart Meter reading on 1st Jan 2021: 7450 kWh
B. Smart Meter reading on 1st Jan 2021: 9120 kWh
Total consumption over 12 months is (B-A): 1670 kWh
Avg. Cost per kWh is ~0.15p (and rising!)
Generation:
A. Total generated as of 1st Jan is 3985 kWh (via Solar Edge)
B. Est. total exported to the grid as of 1st Jan is 3075 kWh (via Smart Meter)
Total renewable energy consumed would be (A-B): 910 kWh
Bulb's Payment per kWh is ~5.3p
Amount saved = £135
Amount earned = £165
Total savings/ earnings for 1st year of installation i.e. 2020 = £300. At the current rate, it will take over 20 years to recover the investment in bifacial solar panels. Let's hope that the government or private sector mandate higher SEG payments or I can see the rooftop solar industry collapsing entirely!

ABrass

Screwdriva said:

Annual Analysis below:
Consumption:
A. Smart Meter reading on 1st Jan 2021: 7450 kWh
B. Smart Meter reading on 1st Jan 2021: 9120 kWh
Total consumption over 12 months is (B-A): 1670 kWh
Avg. Cost per kWh is ~0.15p (and rising!)
Generation:
A. Total generated as of 1st November is 3985 kWh (via Solar Edge)
B. Est. total exported to the grid as of 1st November is 3075 kWh (via Smart Meter)
Total renewable energy consumed would be (A-B): 910 kWh
Bulb's Payment per kWh is ~5.3p
Amount saved = £135
Amount earned = £165
Total savings/ earnings for 1st year of installation i.e. 2020 = £300. At the current rate, it will take over 20 years to recover the investment in bifacial solar panels. Let's hope that the government or private sector mandate higher SEG payments or I can see the rooftop solar industry collapsing entirely!

This was never a system that was going to break even quickly. The self useage in the original quote [70%] was  'ambitious' (as was pointed out at the time) and even the more realistic lower estimates [40-50%] from other users were higher than what you've seen in practice [25%].

In terms of performance it seems to have been doing well for a 4kW system, (even if it was less than the estimated 4,500kWh) but I'd guess it has been limited by the inverter or shading during very sunny periods so it has only managed to be a good 4kW, not 5.2kW.

To reduce your payback period are there any things you can do during daylight hours like sticking the washing and washing machine on? The SEG is awful compared to the old FIT system, it makes self consumption utterly vital to payback periods.

When home batteries drop a bit further in price it might actually make some sense for you. But that's still a few years off imo.

Screwdriva

ABrass said:

This was never a system that was going to break even quickly. The self useage in the original quote [70%] was  'ambitious' (as was pointed out at the time) and even the more realistic lower estimates [40-50%] from other users were higher than what you've seen in practice [25%].

I calculate ~35% self usage (910kWh/2580 total kWh) but your point is valid. We're already at maximum daytime usage (large appliances used only on Sunny days, television and oven only in the evenings etc.)
It's clear we were misled in the original quote but payback wasn't the primary motivation here. Given that 4 out of the 10 panels are West/ East facing roof surfaces, I'm pleased with the performance, just not the financial reward. I expect that electricity costs will continue to rise and, hopefully, a higher SEG tariff will reduce payback a bit. 

Solarchaser

Your total gen was 3985, you used 910.
910/3985 = 23% usage of your generation I'm afraid.

You are going to have to do a lot of solar optimisation if you want the system to pay.

Or get a huge battery ev that you can use for free