The Solar Thread

How does that factor in ?

Well, being wildly optimistic*, you would fully charge the battery with free solar so you’d save £2.70/day which would reduce the break even point to 7.5 years

* This is assuming >10kWh of solar every day (not going to happen unless you have a BIG array), and you use > 10kWh of power from the battery every day (which is pretty unlikely for some months of the year)

DRJ, this is a good question

I don’t know is the answer.. I would have had a nose up the scaffolding but don’t like heights, i thought the only way was with brackets hooked under the tiles somehow.. part of the reason id like my mate to get up and have a quicky snoop, as i literally couldn’t 😀

if you want to see a decent example of  battery control, take a look at “predbat” and there should be some examples of the regime, mine is pretty simple being on flux, just charge as much as estimated to need overnight, although to fill with solar, discharge everything that isnt needed at peak, remain on battery until next charge period, excluding free periods (fill to max capacity in the window, or saving sessions, which dumps as much out). the more interesting agile plans can go up and down throughout the day

10kwh from solar doesn’t seem that wild.

We averaged 10.4 from a 4kw array  in 2023

I dipped into a couple of FB forums and others had build insulation boxes around them etc. Suppose it depends how cold they get in the depths of winter. Ours our in the garage.

Yes, ours is too. I just spoke to our installer and he said sometimes customers built boxes out of celotex but you need to leave room for airflow.

you’d save £2.70/day

Is it really £2.70 a day or are you assuming the solar is lost if not used. There may be an opportunity cost if that solar could be sold to the grid. We feed in at .15p per kW.

This is assuming >10kWh of solar every day (not going to happen unless you have a BIG array),

We have a relatively small 4.8KWp array, WSW facing so not optimal and even in this cloudy and dull year we’ll be averaging about 9KWh per day by the end of Dec.

As above I run predbat on Home Assistant which takes care of the battery charging and discharging, factoring in our typical usage and expected solar generation. If you’re not geeky enough to be into that sort of thing you can just hand control back to Octopus via Intelligent Flux and they’ll take care of it.

We averaged 10.4 from a 4kw array  in 2023

Even in Nov-Feb??!

We def don’t get that from out 4kW array (E?W though).  Also it should be remembered that some of that power will be used by the house as it’s being produced.

Oh.. and AFAIA a 10kW battery actually gives you less than 10kW of power (plus it uses some power to run iteslf).

We have a relatively small 4.8KWp array, WSW facing so not optimal and even in this cloudy and dull year we’ll be averaging about 9KWh per day by the end of Dec.

4.8kW ain’t small…. it’s bigger than the standard 4kW install!

I guess we lose a lot over the winter with an E/W split as we’ve averaged 150ish kWh/month every October for the last 13 years.  It’s good in the summer as you get power early and late but obvs a bit crappy in the winter.

(I am considering putting in a separate 4-5kWh as a ground mount in our paddocks now!)

In 2023 I used 3881kw and I generated 3744kw. The joy of batteries is load shifting -i don’t have worry about when it was generated really it just has to add up.

I almost always charge at less than I export. But I cannot import at peak anywhere near the cost of export.

due to work I cannot use what I generate so I load shift across the peak periods when I return home and am not generating sufficient solar -5-7pm

I charge for free march-october and then Nov Dec Jan Feb I charge over night to varying degrees.

When I worked from home I had solar without batteries (no FIT payment). When I went back to work it quickly rendered the solar useless without batteries without FIT so I had batteries fitted.

That said. What I saved when I fitted counteracts the quotes I had when FIT payment was available. Which were in the 2x,xxx range and panels were in the 150-200w range.

I have the spreadsheet that says this is working currently and on track for just over 5 years payback* on current tariff (subject to change…. Previous version of flux when there was a bigger gap between export and off-peak it was 4.5 years)

Solar at my place has been so good to us DESPITE the internet saying north east Scotland its pointless.   I have installed solar thermal this year in the south aspect dormer and in the days when the sun is out even in October I’m getting 50c in the tank… . Plan to install more PV on the north aspect for summer peak generation so I’m less reliant on the battery -which is 3.6kw limited due to inverter.

Can stick up 3kw of solar for 700quid in parts these days. Mental.

* My parents solar system was installed 2008 and still going strong and generating almost the same numbers as when it was new.

Today is a good autumn day – I’ve generated 14kwh I’ve stuck 9k to consumption -the battery is full – I didnt charge last night and exported 5kwh and at early 3pm I’m still generating and exporting 2kw

Let’s be clear 2023 was a VERY sunny year.  May, June were 800kWh compared to the usual 550-600.  On our 5.5kWp array, A good autumn day will be 21-22kWh, but an average day will be 6-9kWh.  Over a week, that average will be around 12kWh/d.

We import whatever we need between 2-5 in the morning (the max being around 15kWh) and then export pretty much everything which isn’t being used to keep the batteries full.

This way we on average import around 10kWh and export and 2kWh over each winter day (average) Which costs around £1.  Total charge per month in the winter is £30 for power and £17 for the standing charge.  All of that cost is made through the summer with excess export.

Let’s be clear 2023 was a VERY sunny year.

Location dependant.

Year on year

21/22/23 were within 50kwh of each other with 22 being the peak. 24 is looking to be the lowball at 100kwh below the 21 figure -if I use average Nov/Dec numbers. Largely down to a very poor wet may.

Bit like growing veg really.

Our 24 numbers are going to be around 500kWh down on 2023 and if I extrapolate what we had from September 2022 to December, 2024 is closer to 2022 than 23, but I only have 3 data points for Sep-Dec and 2 for the rest.

My point was that for most of the UK (the vast majority of the population is in the south), the 2023 numbers aren’t the best example.  as it’s likely to be around 90% of that.  Also, a lot of people’s equipment was brand new in 2023 and will be dirtier, less efficient etc, so it shouldn’t be banked on.

I switched my North facing 12 panel 5.4Kw system on on Thursday this week after the safety sign-off and meter change. No battery so just selling back to the grid. Incorporating a battery wasn’t cost effective at this point. I’m in Auckland so just in time for spring and summer. Electricity prices and connection fees have gone crazy this year which was the proverbial straw.
$14000 outlay with a future proof 6KW inverter (I’ve north facing garage roof space that will take up to eight more panels if/when I can afford it.

No idea how long it will take  to pay for itself because who knows what electricity will cost here in 3-4 years time.

I hear that in Australia because around 20% of households have solar the buy back rates have bombed and some electricity companies are really struggling to stay solvent

NZ uptake of solar is currently at around 4% of households so we won’t have that problem for a while.

On an Mtb theme given this forum

I’m off to Rotorua for 5 days riding  on Tuesday

 I’m in Auckland so just in time for spring and summer.

Thank god for that!  I was thinking that you must be mad to spend that money on a North facing array in the UK!!

Also, a lot of people’s equipment was brand new in 2023 and will be dirtier, less efficient etc,

My array is 13 years old and I cannot see any discernible reduction in output numbers despite never cleaning it!

I suspect a few days less sunshine would have a much bigger effect on your numbers.

Ours get cleaned twice per year and we can usually see a 5-10% restoration in Max power when they are.  Ours are at 30deg, so if you have a higher incline, they might self clean better.

I’ve just been inspired to check how things are going on my system. Heading into late spring here in Australia and 2 full months to the end of year. Solar wise I’ve generated an eye watering 16mWh and used 9mWh excluding charging the car. Interestingly enough, I’ve pulled 22% of that 9mWh from the grid, but only at deeply discounted rates ($0.08 kWh) or free. We are electric everything. 18kW on the roof in a mix of north (60%), South (30%) and the rest East. East has been the best addition as it just kicks out that couple of kW first thing when you need it. House battery does the arbitrage thing of its own accord depending on weather forecast. The car has gobbled 5.5 mwh, of which 1.6mwh came off the solar.

I clean mine periodically when ever I see bird poo basically.  see no increase. Conversely I also see no decrease in the lead up.

I don’t have the resolution on my data to pick up the cooling effect of the cleaning though.

I bought a long pole and water-fed brush thing to clean the dust off mine once a year, but when I told my installer he said not to bother – it makes no difference and you are more likely to damage them/knock one of the fixings or something. Ours are in-roof and quite steep (maybe 50degrees?) so maybe that’s part of the reason. I certainly couldn’t see a difference in figures before/after i cleaned them even though I could see the dust from ground level.

TBH I can’t see people at solar farms going around washing the panels down!
[….in the UK.  I believe they do in desert based solar farms cos of the think layer of dust/sand that builds up – we have rain to do that for us]

Hope your using de-ionised water !

Interesting to see the subject of cleaning coming up – my father’s panels (installed around 2011) are happily charging his newly installed battery during the day, but I’m convinced the output is down because he has lichen growing across a couple of the panels. AND with these older panels they operate in series so that a restriction on one panel restricts all the others by the same amount (or that’s what I was told back when we had our panels installed in 2013)

I’ve seen grime collecting on my panels recently – not washing off with the rain quite like it used to.

I’m sure we’re coming to the point in the lifecycle where panels that have been installed for 10+ years need a bit of a clean-down, but they’re not an easy thing to get to….

This is the same for me.  From the ground it’s hard to tell how dirty they are but once you’re up on the roof it’s quite obvious and it doesn’t wash off with the rain.

How do you get to them if they’re on the roof?

Are you climbing into the roof?

Sorry, but **** that!  Mine are on a low stable block which I can reach fairly easily* with some step ladders and I’m still not cleaning them!

* I can actually see what they’re like as they’re not far away

Almost every web site I’ve seen says don’t bother in the UK unless you live next to a power station or motorway in which case it may help a little.

If it makes you feel better then fine but anyone who pays to have them cleaned needs a talking too!

(Other than the waste of money, the thought of a window cleaning tool on the end of a long pole being dropped on every panel is quite frightening!)

We have a lower roof and an upper roof.  You can use a small ladder or upstairs window to access the former and then a short ladder to get on the upper roof.  My roof is only 30deg on any slope so very easy to walk on.  I then sit on the ridge with an extendible brush/hose/thing and scrub them down.  The difference is quite something.

Speaking of difference – The first 8 days of November.   Last year  – 90kwh.  This year?  12.  12!  And we’re not even done yet.  It’ll be Monday before we get any proper rays!  We were also 70kWh down on October for the past 2 years too, mostly driven by the dismal final week!

I can see 3/4 of ours from the loft window and the other I suspect could still reach from there with a camera to aid aim. Makes it easy to see how dirty they are. I can’t see how the £300+vat the installer wants to (automatically) monitor them and clean once a year is good value. I’d rather pay the normal window cleaner a lot less or DIY those I can reach easily.

It’s not obvious from a distance either.  Ours look clean from the ground, but it’s like a thin film of dirt (which doesn’t wash off with just water) which is stuck to the panel.  The closest analogy I can given is you know when you wash a car?  Just running a hose over it doesn’t really work to clean it even on the sides and roof which’re out of the direct airflow and even if the car has been recently washed.  Even a jet wash only cleans the areas it’s directed at, the high pressure water which goes to the sides, doens’t do anything, you just end up with clean lines.  This is what I’ve found every time I’ve washed them.  That’s another reason for doing it from the roof ridge, I can get a bit more weight on the brush to clean them.

The first 8 days of November. Last year – 90kwh. This year? 12. 12!

Local news reported that one weather station has had 18 minutes of sunshine in the last 11 days. I’m really hoping they’re right about some blue skies on Monday!

20kwh in the last 7 days. Most days hovering around 2kwh. Pants!

i spent a lot of time on my roof this summer doing other work.

i did actually check to see if there was any build up on the panels…

There was not.

They are 3 years old. – Ill monitor rather than arbitrarily apply abrasion when not required.

Abrasive?! It’s a glass panel with dirt on it.  Do you clean your windows so you can see through them?  Solar panels are no different in that regard.  Windows (which are vertical) will look dirty in months.  Solar panels (at angles from 60-30deg) will get dirty far sooner.  Dependent on where you are, they will get dirty quicker or slower.  But I refuse to believe that a glass panel installed 2 years ago has no dirt on it.  How much that dirt affects generation is related to two factors, absorption and radiation.  My panels are almost certainly more affected by the latter.  Coupled with the roof angle and our location surrounded by fields/dirt, this might explain why I see such a difference.

A solar panel should have rain regularly washing over it, whereas windows are generally sheltered from it, so it might be a little clearer?

Sorry Daffy but I’m struggling to see how you can tell such a difference when there are so many variables plus the fact that panel output is constantly varying.

But if it makes you feel better ?

Maybe some panels have a better non stick properties than others.

I know the flat panels on my van DO need cleaning. They get obviously dirty as they are flat. That said I still don’t see noticeable output issues unless they are covered in green tree sap. Baked on dust seems to be negligible…and that’s on 2*100w panels

But as sharkbait says. What ever makes you feel better.

solar panel should have rain regularly washing over it, whereas windows are generally sheltered from it, so it might be a little clearer?

Our velux windows are on the same roof as the panels, and get dirty quite quickly. But the panels apparently have a coating that means they should clear in the rain.

Who knew. Inspired by ransos post – as I also have velux on the same roof they I DO have to clean regular I Just did some reading and window glass ain’t smooth and will hold dirt on.

Most modern solar panels have a polymer hydrophobic coating hence are designed to be self cleaning.

Rather frustratingly as I’ve only just learned this. It seems I may need to clean my solar thermal regularly….it’s standard glass. FML

Anyone tried rain X or any other off the shelf chemical coating ? I know it will still need cleaning but hopefully not as much ? – if it’s anything like my velux it’ll be down on efficiency quickly

Just coming back to this.  I cleaned my panels in July, so thought I’d pop up for a look:

These photos show the array from a distance, from stood next to it, close up and with one small area cleaned with a damp cloth.  It rained here on Saturday.

i would be wary about using a coating like rainx or a ceramic. isnt there a chance they would limit uv rays and as such performance?