@scoob Hello Scoob,

Very interesting to compare notes! Our system was installed in August 2022; we have an 8.1 kWp. system consisting of 21 Canadian Solar panels spread across four areas. 5 on the house roof facing approx SSW, and 4 on a flat roof with 2 more on a garden workshop roof and 10 garden mounted, these all face more or less SSE. We do have some shading from the hill we live on, some trees and our own chimney - so not ideal.

We have Enphase IQ7 microinverters feeding to a Tesla Gateway thence to 27 kW/h of Powerwall storage. Last year production (according to my Enphase Envoy) was 7.4 MW/h. I am on OE’s Agile tariff and freely admit to manipulating my charge and export settings to fit in with the cheapest 30 minute periods each day (work for retired nerds here!) Ensuring that the import and export rates are most advantageous as I use Agile Outgoing at 15 p p kW/h., can be quite satisfying sometimes. I saw a peak of solar output of 6.0 kW for a few seconds today - best I’ve observed so far this year.

We are all-electric these days and of course the Homely controlled heat pump is the biggest consumer. DHW is supplied via a Sunamp Thermino solar / grid powered 210 litre equivalent unit connected to the Eddi diverter. I usually allow this to charge our system during the cheaper hours in the early morning from grid and any top-up may be from solar during the day. Our daily DHW needs use 3.5 - 4.5 kW/h depending on time of year, there are two of us in a 4 bedroomed well insulated 1930’s semi detached. 10 x radiators throughout and a dual fuel towel rail. The kitchen is well catered for with an induction hob, 2 x combi microwave cookers and an air fryer! Regards, Toodles.

Posted by: @toodles

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I am on OE’s Agile tariff and freely admit to manipulating my charge and export settings to fit in with the cheapest 30 minute periods each day (work for retired nerds here!)

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I recently, in my home automation background reading, came across a few posts on various forums (or alternatively fora, for the grammatically precise amongst us) that are relevant here.

Basically, every time you make a tweak to your inverter's settings that is a configuration change that is written to the inverter's eeprom. The eeprom has a finite write life (some rated to about 100,000, some to about 1,000,000) and although this is an averaged figure with many exceeding that life quite happily, it's still worth being at least a little circumspect about the number of tweaks you make per day. As a result, I personally stick to getting the inverter to react to a smaller number of higher return events (e.g. if the price goes negative, pile into the battery from grid at maximum rate) which means not that many eeprom writes and therefore the likelihood the inverter will survive to at least its expected lifespan.

Doesn't mean I'm right, of course, or that I'm not being over-protective of my kit. Just one of those little things you find out and make a mental note of.

@majordennisbloodnok Let’s take it to the i00,000 writes then and imagine I would like the system to carry on performing for 20 years. 365 x 20 = 7,300. Now imagine I make 24 changes per day every day throughout the 20 years (yes I know I have left out the leap years!) I seem to have exceeded my 100,000 by 75,000! Err…. Whoops! I may have to replace the electronics after about 15 years when the cells also need replacing. I have just checked on my Tesla app for today’s configuration and I note there are 14 changes in all over the 24 hours - I think I’ll take a chance on it probably providing a reasonable lifespan as 15 years will take me into my 90’s and I don’t know if I will be quite so keen a nerd by then.😉 Regards, Toodles.

Posted by: @toodles

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@majordennisbloodnok Let’s take it to the i00,000 writes then and imagine I would like the system to carry on performing for 20 years. 365 x 20 = 7,300. Now imagine I make 24 changes per day every day throughout the 20 years (yes I know I have left out the leap years!) I seem to have exceeded my 100,000 by 75,000! Err…. Whoops! I may have to replace the electronics after about 15 years when the cells also need replacing. I have just checked on my Tesla app for today’s configuration and I note there are 14 changes in all over the 24 hours - I think I’ll take a chance on it probably providing a reasonable lifespan as 15 years will take me into my 90’s and I don’t know if I will be quite so keen a nerd by then.😉 Regards, Toodles.

Precisely. It's not something to suddenly get us all worried about every little write we make; just an extra bit of info to keep tucked away.

My reason for being cautious is that these quoted eeprom lifespans are effectively MTBF figures (mean time between failures, for others like me who had to look that up first time). That means something rated for 100,000 writes could still fail at 10,000, and that'd still be long enough for the inverter to be well out of warranty and yet no longer useable. I don't think the scale of configuration changes any of us have so far described is on an order of magnitude to be concerned about but as automation systems become smarter and incorporate more variables I can easily see implementations that, left to their own devices, would want to make minor tweaks every few minutes or even seconds. As long as we keep those extremes under control I reckon we'll be fine. 

@majordennisbloodnok For some reason, all the diodes down my right side ache now… 😳 Toodles.

Posted by: @toodles

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@majordennisbloodnok For some reason, all the diodes down my right side ache now… 😳 Toodles.

He, he. That's what happens when techies like us wander down rabbit-holes on our voyages of discovery. My brain has turned to jelly and trickled down my spine more than once during my renewable energy/heating quest.

@majordennisbloodnok Unfortunately, solar panels don’t seem to produce much energy when sited down rabbit holes…😉 Toodles.

Posted by: @toodles

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@majordennisbloodnok Unfortunately, solar panels don’t seem to produce much energy when sited down rabbit holes…😉 Toodles.

No. That'd void the warren-ty.

Badoom, tsh.

@majordennisbloodnok That’s all my plans scut ered then.

I have just received my OE bill for April - May and my average unit cost on Agile has worked out at 10.52 p p kWh. I feel sure that this tariff is better for me than Cosy would be. Regards, Toodles.

Now, I know that this may be a little simplistic and perhaps not a true reflection on the actual costs on a given tariff but here goes… (All calculations including VAT but not standing charges.)

My annual consumption (all-electric home) is calculated to be just over 10,000 kWh.

On OE’s fixed 12 month tariff (price per unit = 23.61p.), my annual bill might amount to £2361.

On OE’s Agile tariff (working on an average price per unit = 10.52p.), my annual bill might amount to £1,052.

I feel that the difference (£1,509) goes a fair way towards paying for the Tesla kit over a few years!

As I say, this may all be a little simplistic but is based on present prices and I realise that Agile rates might rocket or (less likely) drop further; at present, I am quite please with my decision to ‘time shift’ my consumption to follow Agile’s troughs. Regards, Toodles.

Hi, im looking into solar for my home, I have been offered 7.8kwp array by a few installers so 18panels. I am unsure about orientating them however as i dont have big south facing roof. We used most electric in the evenings so thinking west facing with some south will be ok.

Would the roofs on the left(south facing) and on right/straight ahead in pic(west facing) in first attachment impact negatively on each other, shading etc? Installer wanted to put 12 on west facing roof in attachment 2 and 6 on south in attachment 1.

I was thinking putting 6 on both roofs in attachment 1 and remaining 6 on nearside west roof in attachment 2. Thinking that further over roof slots on west facing in attachment 2 will be last to get sun. Not sure if that makes sense.