The yearly production forecasts are pretty accurate, it's entirely possible to know your rough ROI before purchasing. Any single days weather is just noise and highly variable.
Solar panel production figures
- Thread starter Ron-ski
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- generation solar
Soldato
I’m 21.8% behind based on yearly forecast. This accuracy is too large a variable to make an informed decision imho. To say clouds for around 3 hours and then sun and X temp the day before only to receive near twice the cloud coverage, rain and a temp that was 4c thus far lower than the day prior when the forecast had it at 3c higher today is a terribly inaccurate prediction. As a child, planning days out was reasonably easy. The forecast was reasonably accurate, planning the same now isn’t as easy and with the tech we as a species have now vs 30yrs ago we should be doing better.
I’m still minting it from the solar, it was still a great investment however if I had factored in a 21.8% reduction in production I wouldn’t have taken the solar on as a movement in the wrong direction with unit costs could upset that balance, look at what the government is planning on doing to the Australians! Charging them for sending it back after making the investment for a cleaner future. I think the UK will get similar ideas knowing what we have at the helm now.
15.4 and 19 over the weekend, i dont really measure like some in here against "forecast"
I do however check against what my predicted outputs were from install which indicated circa 2400kwh a year and I've hit best part of 3000kwh so far in the 2 years its been installed
I do however check against what my predicted outputs were from install which indicated circa 2400kwh a year and I've hit best part of 3000kwh so far in the 2 years its been installed
Associate
Poor start same as Sunday but got a bit more at 23.90Kwh in today on the house no hot water and no export either but the battery's got to 98%
The work shop made 6Kwh and a full battery no export
House System is East West
down in not so sunny Devon.
East 8 x 420w panels 45 deg pitch
West 10 x 420w panels 45 deg pitch
Givenergy Gen3 5kwh hybrid
2 x 9.5 battery's
Workshop system is South/East
2440w of panels two 720w strings
one 1000w string
Hybrid inverter with 4x 12v 100Amp
Battery's
Plus grid tie inverter as well
The work shop made 6Kwh and a full battery no export
House System is East West
down in not so sunny Devon.
East 8 x 420w panels 45 deg pitch
West 10 x 420w panels 45 deg pitch
Givenergy Gen3 5kwh hybrid
2 x 9.5 battery's
Workshop system is South/East
2440w of panels two 720w strings
one 1000w string
Hybrid inverter with 4x 12v 100Amp
Battery's
Plus grid tie inverter as well
Another nice day, although a few more clouds around late afternoon, 41.89 generated and 36.07 exported.
Short answer, you can't.
The annual estimated generation is usually lower than the reality, my system installed in December 2015 was estimated to generate 3758 kWh a year, every year it has out performed that.
2016 - 4360
2017 - 4390
2018 - 4370
2019 - 4380
2020 - 4510
2021 - 4150
2022 - 4620
2023 - 4290
As you can see, its performed far better than expected.
But, the biggest factor on ROI is how much electricity costs, and how much you get for export, and how your usage changes, these three things are for more complicated to know, the first two impossible, the only one you can control is your usage. So in reality you can only make an educated guess at ROI.
My estimated ROI on that system was 7.88 years, somewhere I had a spreadsheet where I worked out when ROI was, it was back in 2021 or 2022, probably 2022, mainly helped by the big increase in electric costs.
Short answer, you can't.
The annual estimated generation is usually lower than the reality, my system installed in December 2015 was estimated to generate 3758 kWh a year, every year it has out performed that.
2016 - 4360
2017 - 4390
2018 - 4370
2019 - 4380
2020 - 4510
2021 - 4150
2022 - 4620
2023 - 4290
As you can see, its performed far better than expected.
But, the biggest factor on ROI is how much electricity costs, and how much you get for export, and how your usage changes, these three things are for more complicated to know, the first two impossible, the only one you can control is your usage. So in reality you can only make an educated guess at ROI.
My estimated ROI on that system was 7.88 years, somewhere I had a spreadsheet where I worked out when ROI was, it was back in 2021 or 2022, probably 2022, mainly helped by the big increase in electric costs.
Associate
16.7 and 9.8 exported. Bit of a weird day. Had a very weak storm early on, then sunny, then cloudy but bright, then went sunny again around 3 ish.
Soldato
16.8 for today…
Associate
33.8 generated and 22.8 exported.
Pretty cloudy at times and of course warm which dulled the production, but still decent.
Pretty cloudy at times and of course warm which dulled the production, but still decent.
Soldato
23.8 rather good today, still choppy - need a cloudless one to see what gen I could hit.
Soldato
34.68kWh generated today. I am surprised it is as low as that but again a terrible mid-morning period did the damage.
Re ROI calcs etc... I am at 108% of my target month-to-date based on the installer's annual generation prediction/forecast. I think the estimated numbers for ROI calcs etc are generally on the conservative side - I've had several days in August already that have been way, way under what I'd expect and yet here I am, ahead of target. My bills have dropped from roughly £8 a day to around £2 a day on average. That includes charging an EV that we didn't have when we were at £8/day. A linear extrapolation of that (which is not entirely unreasonable given I am time-shifting to cheap rates using the battery) would mean an annual saving of ~£2200 but of course with the export it is even better than that, perhaps +£1k annually on the conservative side. I did a big deep dive into the ROI calcs and it came in at a shade under 5 years. I appreciate it is early days for my system but if things continue the way they are (as it has for example with Ron-ski) then I'll smash that, regardless of how good or bad the Met Office are at forecasting the weather...
Re ROI calcs etc... I am at 108% of my target month-to-date based on the installer's annual generation prediction/forecast. I think the estimated numbers for ROI calcs etc are generally on the conservative side - I've had several days in August already that have been way, way under what I'd expect and yet here I am, ahead of target. My bills have dropped from roughly £8 a day to around £2 a day on average. That includes charging an EV that we didn't have when we were at £8/day. A linear extrapolation of that (which is not entirely unreasonable given I am time-shifting to cheap rates using the battery) would mean an annual saving of ~£2200 but of course with the export it is even better than that, perhaps +£1k annually on the conservative side. I did a big deep dive into the ROI calcs and it came in at a shade under 5 years. I appreciate it is early days for my system but if things continue the way they are (as it has for example with Ron-ski) then I'll smash that, regardless of how good or bad the Met Office are at forecasting the weather...
Associate
48.50 kWh and 29.10 kWh exported - not bad considering the hazy clouds, rain, thunder & lightning and another new inverter fitting! 
Soldato
36.5, slow start
Associate
Yesterdays - 13.60 generated and 6.80 exported
Soldato
So panels thoroughly washed this morning, heading over to the mainland for this afternoon! It probably wont reach Ronski over Wednesday but that's if the forecast is somewhat accurate..