The Solar Thread

Can anyone comment on their experiences of withdrawing credit from their Octopus account please.  It took 2 phonecalls to get it set up and I thought I was setting it up so that i could do it all online thereafter.

The first time I withdrew credit it took 23 days.  I phoned them and explained I thought I’d set it up so I could withdraw credit online, the fellow I spoke to told me I’d have to phone each time I wanted to withdraw.

I phoned to withdraw credit again on the 7th and this was showing on my account as pending, but has now disappeared, everything is hassle with them so far.

I’ve only withdrawn once but I’m positive I just did it online.

Flux export was really fast for us – 14 days after signup and it was all done.

In general, Octopus have been pretty great.  Everything has been done exactly when they said it would and did what it was supposed to.

I only joined in June and am already sat on £200 worth of credit for a single £30 direct debit.   If we can get to October with £300 in credit, that should see most of our winter usage paid for and maybe a little paid toward the standing charge.  We won’t be totally cost neutral, but using off peak to force charge the batteries, we may be able to come close, so circa  £2000 saved this year, maybe a little more, but that would require the British summer to arrive some time.

We tripped over onto the grid (0.15kWh for 2 hours) for the first time this morning since early March.  A combination of heavy oven use on Thursday evening with utter abysmal generation through the day (4.3kWh) meant we were a little short before sunrise.

A question on inverter and battery efficiency.
On the current flux tariff, import cost between 02:00 and 05:00 is marginally cheaper than the export rate (aside from 16:00 to 19:00)

given it’s cheaper to import than export why not charge the battery fully between 02:00 and 05:00 and do any high draw activities form the grid. Then during the day you will export a greater amount

muddyjames: thats exactly what I do. Though I suspect that with losses the gap between 0200-0500 buying and daytime selling is close to zero. What it does mean however is full battery every day irrespective of the weather. I also force discharge at 3kW between 4pm and 7pm. So about 9kWh discharge, leaving 3kWh approx to run the house between 7pm and the next 2am slot. Tweaked settings to maximise sale but also ensure enough remaining in batteries at 1901 to last a typical remainder of evening.

Those settings I suspect I will keep all year as the only variable really is solar yield and surplus of that goes straight to flux export.

Solar newb here – we were fortunate enough to get a fixed tarrif just before energy prices went mad, but now that’s coming to an end and that’s probably the final shove we needed to do something about solar plus battery etc.

So, first question – is there an unbiased idiots guide anywhere that will let me work out how many panels to put where (tiny bit of roof faces S, most is more or less E or W), what size battery makes sense etc.

Second question – how to find an installer and what questions to ask them (Swinley area if anyone has a recommendation)

And finally for now – MrsP is a structural engineer who wants lots of stuff about roof loading, fixing systems, maintenance etc – any helpful resources there?

Number of panels is dictated by the size of the roof, the size (both capacity and size – the former drives the latter), the inverter and in some cases the mounting system. Also what the customer wants,

Most panels are affixed using brackets to the roof joists modifying the tiles and sealing again often using leadwork.  The panels aren’t usually a huge weight compared to the tiles.  A typical 1.8*1.2m panel will be around 18kg, so 20kg per panel with the brackets.

If installed on-roof as above, you may want some protection (mesh netting) around the edges of the panels to stop birds nesting underneath them.

Mine are slightly different as mine are in-roof.  Essentially, the tiles are replaced by overlapping plastic mounting trays and the panels are attached to these with a border of tiles and galvanised steel.  The roof weight is now lower with the panels than it was before as almost 100 concrete tiles are removed.  There’s also no need for bird protection and, IMO, it looks better, but they will be slightly less efficient on VERY hot days, maybe 5% as they have less convection cooling.  In roof is around £2k more expensive.

Batteries and sizing are tricky.  Cost effectively, smaller batteries and a good tariff and management will work great, but if you want true self sufficiency, bigger batteries will do this, but the economic argument loses weight.

In a gas heating cooking household, 5kWh is probably around the right value.  In an electric cooking household, maybe 10kWh.

Hope this helps.

Thanks Daffy – some great info. Our current energy supplier says we’re using about 3300kwh per year but I’d want to leave headroom for when we finally get an EV.

In roof is around £2k more expensive.

Is this just for fitting to an existing roof? We’re building a new extension and I’ve currently specced in roof as I figured it would be cheaper (due to fewer tiles) than on roof

Your best bet is to get a couple of quotes rolling, they can make a pretty good estimate from google maps

i used a company called dual fuel solutions and i have no complaints, and the pricing was competive, and they were flexible with my quotes until we got where we needed to be, installation from first quote to sign off was 12 days… insanity, if you speak to them please mention me as a referral (PM’d)

Battery sizing, i figured bigger was better, as its easier to keep a little in reserve, for a bad day, or a missed low cost charge etc

On a new roof it should be slightly more expensive, but not by much.  The tiles will be about the same as the trays, so cost neutral. But the steel sheeting, sealing, extra wood work and bolts will all add up.  Labour will almost certainly be higher too, especially if tiles and ridges need to be trimmed or shaped.

To keep ours near perfectly centred in the roof, every border needed all the tiles trimmed after careful measuring.

Hi All, apologies if this is covered elsewhere, but what are the best online resources for interfacing third party apps, raspberry pis, controllers etc to one’s inverter ?

Ta.

Usually people use Home Assistant through a Pi to perform the interface.  Some inverters and Batteries can be directly connected.

Most panels are affixed using brackets to the roof joists modifying the tiles and sealing again often using leadwork.

They cut a slot in the slate tile for the bracket which goes under the slates against the joist. A plastic sheet sits over that and then they replace the slate tiles. Takes a while as each bracket requires two slates to be notched by hand using an angle grinder.

Solar install by Ben Freeman[/url], on Flickr

Solar install by Ben Freeman[/url], on Flickr

Solar install by Ben Freeman[/url], on Flickr

Solar panels on South facing part of the roof by Ben Freeman[/url], on Flickr

Looking out of my office window it does not look like our tiles were modified. The mounting system has stainless bracket that slip under the tiles.

Looking out of my office window it does not look like our tiles were modified. The mounting system has stainless bracket that slip under the tiles.

Depends on the tile design. If you do that with slates you’ll end up with flying tiles.

Odd question, I’m keen on Solar but concerned of hassle(cost) if we need to replace the roof in the next 10-20 years.

Has anyone fitted solar and then paid to have it removed and refitted for roofing work?

Was it expensive?

Current roof in good enough state to justify not replacing it as part of Solar install.

Cheers

@jacobff.  I got a real finger in the air “£2k” to remove 16 panels so I guess you’d need to add a bit more to put them back up again.  Hope that helps, that’s a big ol’ dent in the payback hey – I only know this as I was weighing up getting a 2nd array that we felt we may want to remove for the purposes of selling the property as it’s a period cottage

I got my whole roof/gutters/soffits redone at the same time just to make sure this didn’t have to happen.

Truthfully though, I’m not sure how much of a big job it would be – If the scaffold is going up anyway to fix the roof, the panels are held on my a few brackets and an electrical connector.  They’re not heavy and can be easily stacked.  You’d likely need to get someone back to reinstall the brackets once the membrane and battons are replaced, but most of the hard/technical work would already be done.   Panels are already up there, wiring is already in place.

Current roof in good enough state to justify not replacing it as part of Solar install.

But not in a good enough state for the lifetime of the panels? Pesky. I’d suggest sort out the roof now and then no problem in 20 years.

It was easy for us, the roof needed replacing before the panels went on.

Likewise, we did the roof first, then added panels.

Realised I didn’t update this for August:  5.5kWp array, south facing, in the southwest with battery storage.

613kWh generated,

280kWh exported,  (£66 paid to us by Octopus)

16kWh imported.  (£21.62 paid by us to Octopus inc standing charge)

£44.50 profit.

Anyone able to comment on the effect of hot weather on the output of their system?

Mine is an old system, 11 years now so well past it’s pay-back period, but still well within FIT payment timescale so not worth replacing yet. I had to replace the inverter back in the winter so this is the first year I’ve had real-time stats of what they’re producing.

On these significantly warm days, I’ve noticed my max output is 1.6kW, from a system that is rated at 2.25kW – so down about 25%. Can anyone comment – are you guys seeing a similar reduction?

Edit – I should point out that on cold days with a sudden sunny spell I get up to 2.5kW out of the system, so I reckon it’s heat not simply age/deterioration…..

Lots of variables at play I suspect. Although very hot and sunny at the mo the sky is certainly not as clear as it is on those crisp sunny winters days. That takes the edge of it a bit. Mine was showing a max of just over 4.5K today. It can often go above 5.5Kw (Theoretical max of 6KW). Also my roof angle is quite steep so gets better maximum output in winter when the sun is a bit lower than it does now in summer. And when were your panels last cleaned. Maybe some summer dust on them?

I’m in Spain currently so can’t even use my output but my system 4.14 panels 3.6kw inverter with batteries

I’ve been producing 5.2+ this week and the garden weather station showed 32degrees. .

Panel output degrades with heat.

August (4.2kW array split east/west, 3.7kW inverter, battery storage and EV).

Generation: 429 kWh.
Inverter calculated export: 280 kWh.
Import: 171 kWh.

Overall for August: £55 profit. Not brilliant but weather was awful. Full year generation of 3,600 kWh, exactly as predicted by the installers.

4kw array heavily shaded 🙁 4.2kW of batteries.

Generation 405.8kW

Consumption 196.9kW

of which Battery charging 81.7kW

Energy from grid 30.1kW

Export to grid 210kW

I think thats ok but i dont really know?

Well, I’m a month in of having added my solar diverter and it really isn’t going to be worth it. I kind of expected it, our array doesn’t produce much and we use alot of what’s generated.

I’m consoling myself that it’s nice to get a view of what I’m exporting (already had a view of generation total from the FIT meter and live generation from the octopus Ihd)

Well August wasnt the best month, but not too shabby.

18 panels (10 facing east, slight 15° towards south) 8 facing west (slight towards north)  12.8kw battery set to discharge/recharge to about 25% each day before recharging.

In Leeds we got 677kWh solar, with domestic usage 377kWh.

Combination of surplus solar and Lux/Hanchu battery load shedding we exported 696kWh at an average of 23.81p and imported 477kWh at an average of 17.86p.

Total for the month, about £60 profit even after standing charges etc.

So far in past 7 days we are £18.5 up, mainly due to sun since the weekend.

I’m a little disappointed by our generation this week.  It’s been uniformly sunny, but we’ve struggled to exceed 4kw of generation at peak power.  That’s on a 5.5kWp array with no shading.

I’m going to try cleaning the panels on Friday – they’ve been up for a year and are at quite a shallow 30deg, so maybe it’s just dirt…?

Octopus billing problem: has anyone one else experienced this.

We were swapped from Bulb to Octopus in April this year and all was well I thought. In June I noticed I wasn’t getting billed for electricity used, gas and export were fine. The app showed they were getting all the data, but no bills. It took a number of unanswered emails and finally a phone call to sort this, and now my August bill, and Octopus aren’t billing me again for electricity! Has this happened to anybody else?

it took about 3 months for me to get a bill properly.

Yeah this week has been epic for me. Perfect parabolas since Saturday.

28kwh/day

And as I’ve used zero I’m up about 19-20 quid

Octopus billing problem: has anyone one else experienced this.

Yes. I’m in my third year of Octopus supply and I still can’t work out what the hell is going on most of the time.

I do get a bill once in a while and I go through it and it checks out, also the app shows me stuff in terms of usage so I know they have the data, it’s just weird that they don’t seem to have it automated.

@daffy, I’m assuming your baseline is actual data from a year back? (rather than an unreasonable expectation of what you’d generate?)

At the other end of the scale: 12 old panels in a valley (so partially shaded) and East:West (so presumably not as good as 12 all south facing).

Yesterday: 8kw generated!

I think it’s the heat holding them back rather than any kind of problem but what’s people’s view? – get someone out to service/assess they’re all working fine? Get up there and clean them?

My challenge is I don’t have much in the way of reporting from 12yrs back to say that the generation would have been any different back then

My array wasn’t activated until late November last year, but was installed in September, so no data to directly compare to.  What I’m comparing to is generation in March and May.

in March we were getting sustained peaks of 5.3kW, in May, it was sustained at 5.2kW, the rare days in August when it was sunny for longer periods were 4.6kW, now we’re down to 4-4.2kW.  It could be simply what happens in September with the sun at a less than optimal angle, it could be dirt, temperature or something else or even a combination, but I think cleaning has to be the first step.

Our generation of the last 4-5days has been around 30kWh a day.

Ah, got you. I’d be surprised 9 months later if you’re experiencing degradation as a result of dirty panels but it’s a nice easy action to take

It could be simply what happens in September with the sun at a less than optimal angle, it could be dirt, temperature or something else or even a combination, but I think cleaning has to be the first step.

Mine are the same. I doubt it’s dirt – we’re just a long way past the solar irradiance peak of mid June and you should expect similar generation capabilities to early April. Couple this with hot panels and the output looks about right.

FWIW I have a 12 panel east/west split and generated 14 kWh yesterday. That would have been 30 kWh in June. Not helped at this time of year by tall trees to the west of the house.

August figures for us:

Production – 957

Import – 275

Export – 705

Net profit from Octopus for period 20July to 20 August was £91

Octopus give the breakdown of which rates we export at on flux.

We sold: 545 kWh @ 19.3p and 155 @31.4p

Had a quick look at production peaks vs temperature. Comparing two very sunny days. 8th June, whole day average temperature was 14.9, peak output was 5.86kw. This Monday, average temp was 20.9 and peak was 5.01. Panels are 2 years old and never been cleaned (its on the list!)