Anyone Else Able to Share Some Solar Panel Figures

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sizbut
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Joined: 2 Oct 2018, 11:56pm

Anyone Else Able to Share Some Solar Panel Figures

Post by sizbut »

Just has a set of solar panels installed, and before I get into an argument with the installers, I wanted to get some idea of what I should have been expecting from it for the last few days.

Located just south of Cambridge, its a 2.8kW system on a 30° roof facing just 20° off due south and unshaded.

For the last two days it has produced just 0.5kWh each day, running at a reported almost constant 50W between 8am and 7pm. Whilst I know its been pretty grey and cloudy, that Wattage still comes out at under 1.8% of the system's potential.

But without any experience I don't know what sort of ballpark figures I should be expecting. So any comparison figures would be much appreciated.
rjb
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by rjb »

0.5 kwh seems very low i think you need the installer to check it out. My solar panels 4Kw array generated 3Kwh overall yesterday on an overcast wet day, ie the total over the whole day. My panels point due east, no idea of the roof angle but it shouldn't make a great difference. On a sunny day 4 days previous it generated a total of13Kwh. Even on an optimum day during midsummer my generation would only ever achieve a max of 3.4Kws when the sun is highest in the sky. :wink:
Over 12 months I generate approx 3200kwh, of which I use 1600units, split equally between heating the immersion tank and the domestic load. The remaining 1600units are sold to the grid.
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
sizbut
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by sizbut »

Rough maths puts your system at an approximate average of 270W during the day and 3.25kWh total per day. Proportionally, on mine that would be around 200W and 2.4kWh per day - certainly not the 50W and 0.5kWh I'm seeing reported.

Even allowing for different orientations and locations, that supports my feeling that something is wrong in my system. Your figures give me some confidence that I'm not being naïve, so many many thanks.
rjb
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by rjb »

We don't have a battery backup which is now becoming more common. If you have this you could be charging your battery which could skew your readings but I can't comment on such systems. :wink:
Typical monthly output for December was 60 kWh, rising to 500kWh in June. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
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simonineaston
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by simonineaston »

As an amusing aside, the newly formed residents' association learned recently that they are dozens of solar panels atop our flats and that they are busy producing and supplying 'leccy on behalf of the development's original building company...
all that lovely lolly...
all that lovely lolly...
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
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[XAP]Bob
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by [XAP]Bob »

2.4kW system, ten degrees off south 32 degrees vertical - a little over 0.1 degrees further north than Cambridge.

Last week has had quite a few poor days... 9.5, 9.3, 2.7, 9.1, 1.7, 1.7, 8.4 but I've still only imported a total of 2kWh peak electrons (basically battery reaction time "leakage") across the week. I had a 0.6 on the 9th March, but other than that one day since the start of February I've had over 1 consistently - averaging 4.6 in March.
If you're getting only half a kWh then you're not getting what you should... there is probably something not right.

Your "good" days should look more like (this was an 8.4 day):
Screenshot 2023-03-31 at 10.08.40.png
Your "completely overcast" days more like (this was a 1.7 day):
Screenshot 2023-03-31 at 10.09.01.png
its a 2.8kW system
Do you have micro inverters, optimisers, or just a string on a simple main inverter?
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
sizbut
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by sizbut »

rjb wrote: 31 Mar 2023, 8:56am We don't have a battery backup which is now becoming more common. If you have this you could be charging your battery which could skew your readings but I can't comment on such systems. :wink:
Typical monthly output for December was 60 kWh, rising to 500kWh in June. :wink:
It does have batteries, but the reporting it is providing show them just sitting at 48% and everything being generated being consumed by me.

Today is 100% cloud and it's reporting 49Watts, yesterday afternoon was clear bright sunshine and it reported running at 50Watts. It's both the low figure and the way that it shows only a slight variance to conditions that puzzles me - my suspicion is on the reporting.

Anyway, I've informed the installer now asking them to send someone to check if the system is operating correctly. Fortunately I haven't paid yet and the scaffolding to check the panels is all still in place.
thirdcrank
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by thirdcrank »

I have just received my quarterly Feed-in Tariff payment for the period 25-12-22 to 25-3-23.

Over that period my 4 kW system generated 375kWh.

I don't see what use that information is to you but as I have it readily available it's not a big deal to share it.

I would say that when I bought our system November 2011 there were regulations about what predictions could be made about system generation. The salesman surveyed our roof for orientation and angle etc and included that info into a simple graphic with latitude (from the OS reference ?) That gave an officially-approved prediction and according to him it was all he was allowed to offer. I've still got all that stuff filed away somewhere and it was, if anything, an underestimation.

So, I don't understand if you feel that you were mis-sold the system or if your system has been wrongly installed.

It's now history, but our account was initially mired in problems, mainly caused by the electricity supplier making a total cock-up of our paperwork which led to a lot of grief.
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[XAP]Bob
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by [XAP]Bob »

Yeah - that's not right, you should be generating peak power in sunny spells (or even more, given that the panels are new and the weather is nice and cold)
How much shade is the scaffolding casting on the panels?
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Manc33
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by Manc33 »

The light difference between sunny and overcast is massive. Years ago I wondered about it and my dad measured it with a light meter - an overcast day had 16 times less light than a sunny day.
We'll always be together, together on electric bikes.
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[XAP]Bob
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by [XAP]Bob »

And there is massive variation in "overcast" - if you look at the 1.7 day graph I shared earlier then you can see that the power varies between 400W and under 50W.
None of that is direct sun - the 400W is still lower than the bottom end of the "sunny day", and our sunny days have had significant cloud coverage.

(all numbers taken in the middle part of the day)
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
rjb
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Location: Somerset (originally 60/70's Plymouth)

Re: Anyone Else Able to Share Some Solar Panel Figures

Post by rjb »

simonineaston wrote: 31 Mar 2023, 9:29am As an amusing aside, the newly formed residents' association learned recently that they are dozens of solar panels atop our flats and that they are busy producing and supplying 'leccy on behalf of the development's original building company...Screenshot 2023-03-31 at 09.28.12.png
are you getting any benefit? Those schemes often reward flat owners with free electric if the solar generation exceeds the demand. :wink:
Are you and the panels insured against the odd 6. :lol:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
sizbut
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by sizbut »

No, the scaffolding is below the height of the panels (says the man who just went outside muttering "should have checked that".
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[XAP]Bob
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Re: Anyone Else Able to Share Some Solar Panel Figures

Post by [XAP]Bob »

sizbut wrote: 31 Mar 2023, 12:27pm No, the scaffolding is below the height of the panels (says the man who just went outside muttering "should have checked that".
Really easy to not think about - particularly if you knew (subconsciously) that they weren't shading the panels.

Optimisers etc?
What are you using for measurements?
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
sizbut
Posts: 212
Joined: 2 Oct 2018, 11:56pm

Re: Anyone Else Able to Share Some Solar Panel Figures

Post by sizbut »

At the moment I'm just using the readings provided by the inverter. If I'd had my brain switched on I'd have been taking daily readings from the two new meters they install downstairs to see if they were giving the same kWh results.

(That said, I can still check if they total the same cumulative reading.)
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