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So, fun times... I'm not overly bothered selling surplus solar back to the grid, as I dont envisage producing much more than I need for myself on a daily basis in the summer.
However, I thought would have a chat with the folks at Octopus to see what I might need to do to sell back power from my batteries.

My DNO UK Power has already agreed that I can push 6kWh back into the grid from my battery system should I have the surplus power to do so.

Octopus's claims of not requiring MCS certification at the back of last year appear to be a bit of hot air and some beta setup IF you pay £250.

I asked to move to one of the export tariffs should I go on holiday and have surplus solar (Not likely this summer !!), the request generated some automated responses namely, asking for my MCS approval. I dont have AC solar so its only going to come from my DC batteries right now, I provided my certificate for UK Power networks G99 but that resulted in a bounce back by a human suggesting it wasn't the MCS document they needed.

I mentioned the Octopus no longer requiring MCS certification and they responded by saying that it was by invite only but I could join a waiting list for £250 quid. Now with a couple of panels at the moment I'd never get the cash back ever not to mention the ongoing MCS costs.
So I thought it over and said stuff it, I'll skip for now and keep my own power to myself.

I got to thinking - What exactly does MCS certification get me? It seems like a health and safety exercise which is a bit like closing the gate after the horse has bolted for all those systems built like mine that didn't need MCS. If its this important why dont they just mandate that ANY solar needs to be MCS approved?.

I've also read that Octopus has riled up some of the suppliers by this move, the 3rd parties have put people through MCS approval courses/training, I understand that, it does seems odd that our surplus energy is now not going to go back to the grid due to seemingly more bureaucracy.
This seems a bit self defeating although I would imaging the annual renewal of an MCS certificate is a nice little earner for some companies.

I'm now tempted to add a few more batteries to capture when I generate and be done with it.

The good news is the ground mount Solar Charger is now installed and waiting for me to buy some panels after I build the green leanto shed kids play area thingy.



After a nightmare month for things to break; our 25 year old fridge gave up the ghost, there was no point keeping the matching freezer that we got at the same time (Likely that it wouldnt be far behind the fridge) and we've had to replace them with a large combination fridge/freezer and is rather more efficient. Overnight I'm seeing lows of 130w low to 275-300w high. I reckon its saved me half a batteries worth per day.

Back to reviewing the design and see how much cash I have left after the most recent install So I can start to chop my hedge back!!.

Hi Tay,

Very much echoing my own thoughts on this. Have you kept an eye on your smart meter export number? That is worth doing as you grow the system? We don't export that much as the Solar iboost system catches most of it. Probably about a 1/4MWh pa (maybe), could be close to 150kWh pa export but I stopped tracking it a few years back.

The more you can put in yourself (diy build), store and use yourself the better. Although it is all highly personal to your set up, ethos etc. An example of that would be that I could probably slip back into piped gas use for heating as the prices are dropping and export on my MCS cert including my DC build in that and run at a profit due to the disparity in pricing between gas & export? I don't know what Octopus export price is set at so I am genuinely just surmising.

As i say its all highly personal to mindset and power use circumstance as well as i suppose Geography (orientation as well as latitude). Some of the lads in the South have serious generation. Which solar controller do you have (or plan to)? I went Victron 150/60 solar charge controller with an intermediate step at 100/35 (I think). With hindsight i'd rather have went big, that's in panels storage and charge controller too!

In saying that, the original plan grew arms & legs as we realised how smashing it all just was. So its a 20/20 hindsight moment there. I think we've got about 11kW of panels through MCS or DC direct (give or take) and about 1.3kW AC via micro's. The AC micros option has been an eyeopener for me. Little cost, little impact to do and best of all you don't have to ask anyone to do it.

Gonna go a bit trippy now. The penny really dropped for me when I backpacked an Enphase IQ7 micro inverter out to Turkey to the house there. Got my cousin who doesn't have a clue about engineering to help me hook it up for a test. "Keep an eye on that light Brian, let me know when it flashes orange". He duly did that and then i said that's the house getting electricity in from the local star. He looked at me like i'm nuts! A fair point and true yet not for that particular truth.

I said "its like magic, eh cuz"? His wheels were blown at the reductive simplicity of tagging the house into the star. That was a good day.

P.S, I fly about 8 flights per year, sometimes 6 and a large part of my gas denial has been to compensate for a lifestyle that I have no intention of dropping. I thought it fair to be honest and forward in that so i'm not dumping on anyone's way. Cheers!

P.P.S Tay are you pulling from the grid at all?

Yup, I know what you mean.

I'm currently running a Victron SmartSolar 150/35 for the 2 panels on the pergola, this was the eye opener for me, i've seen days where I've generated 7.5Kw's which is half me daily usage currently.

The new ground mount will have 4 x 575w's panels and the controller for that is a Victron 250/60 as those Canadian Solar panels really kick out the juice, if I get similar results with those panels I could be seeing something in the region of 21-23Kw's per day or more as there is no early shading on the new four panels (When they go in of course), as I'm off for a week in the Isle of Man soon its not going to get built in the next month, maybe a chance for panels to drop in price a bit.

I've halved my draw from the grid, and what I do take is all off peak now too, Not used peak priced power since end of March. Leccy bill has dropped significantly, then I've got the storage heater experiment for winter, I suspect I'll be on the off peak tariff by then too, so hammer the off peak for those heaters in the winter.

I'm currently on Octopus Agile which is fun and although I've not sat down to work out whether its better than the standard off peak tariff, its more fun charging in specific windows and avoiding others.
That novelty will wear off soon I suspect. a few times I have hammered the crap out of it due to plunge pricing but still I don't think that it'll be better than the pure off peak in the longer term.

Once I get 3kWh of panels up and running that should hopefully give me some reasonable winter returns. Thus far the handle shade well, product a ton of power

What I need is lots of days like this.



As opposed to todays ^^




I think I'll be looking at something along the lines of the iBoost going forwards (and A/C for that matter) but that might be some time down the road.
if they dont want my power then sure as sh1t stinks I'll find a way to use it myself.

One thing about the installation of the 250/60 today was that my Lynx busbar is now full, there are ways to expand it but I think any other panels I put up might just be ad hoc ones that will go on the MicroInvertor, my LonghI 435 City Plumbing panels were perfectly suited to the M/C and that'll make a nice dent in the AC usage without taking the 3-4% hit on DC/AC conversions. The Victron is smart enough to handle any surplus AC on that side of the connection and push any surplus into the batteries as DC - I just wont get decent reporting.

You can see why I decided go with a chunky charge controller as these panels are quite lively in the sun/cold..sometimes they were quite high on the V and A's and I need to keep that 10-20% buffer.

Also tempted to stick a diode into the cabling if I use the 435's on the microinverter for prolonged use just to drop the volts a tad lower. or maybe get a chunkier one

Tay wrote: ↑Tue Jun 18, 2024 8:00 pm You can see why I decided go with a chunky charge controller as these panels are quite lively in the sun/cold..sometimes they were quite high on the V and A's and I need to keep that 10-20% buffer.

Also tempted to stick a diode into the cabling if I use the 435's on the microinverter for prolonged use just to drop the volts a tad lower. or maybe get a chunkier one

The Victron solar controllers DO have built in throttling. It is in the at times hard to find (for me) literature. We bounce off of our 60A limit all the time. As to voltage, you'd set that in your string design surely? Although I could see how it could be a worry if running strings of for example 4 on 40V peaks I run strings of 3 give or take about 40V.

The give or take is where I like to be, I.e well under the solar controller limit. I know that sounds simple but I'd rather undershoot than ever worry about cold bright days.

Pretty sure it was Nowty that taught me to look for the noc on panels. Used to be about 35V per panel, now up about 40v with the efficiency increases. Therein lies the difference tween a 3 or 4 panel string on a 150v solar charge controller. As to the Amps, I like to cast a big wide net to catch as many solar fish as possible. Hence the due diligence on the self throttling ability of the solar charge controller regarding power flow (A).

Being far North I have to sift more. Hence the bigger net. I might if funds allow step up again from the 150/60 Victron but I'll have to do some sums to ensure I won't be overcharging the batteries at solar peak with a higher power flow through a larger rated Victron unit. It may be that the bms onboard the Pylontechs would sense the excess combined flow from both the Victron and the Solaredge and throttle themselves but I don't really want to go there, not for a unsafe couple of kWh's per day... That's a maybe btw, I really haven't looked.

A day of sums if I go further I think. Hope the aforementioned acts as a kind of teaching tool/heads up for other fellas? Or at least a 'beware' roadsign.

I'm able to push 100A in to the batteries, but most of the time I run it at 90-95A, slower is better I was told, obviously for me thats from the mains but even so, unless I really am tight on time it generally sits lowish.

When charging with the 6 full panels up I'll drop the SOC to around 75% if its gonna be a good day but with our weather nothing is a given.. its harder to cock it up with just panels.

I've been looking at the possibility of adding some PV on the DC side and found the Victron MPPT calculator to be very useful as it lets you know what is acceptable to their solar controllers and what isn't.

I got a lot of time for the VIctron kit, I've really happy with the choice I made going towards it. I love the fack it throttles power nicely, my mate with the big twin Fronius unit has trouble with his, despite them playing nice with the Victron kit. The frequency shift stuff seems to clash with somethign he has causing issues. Probably his cooker clock ^^

I was surprised by how much bigger the 250/60 charger is to the 150/35



Its a bit of a beast, can't wait to get back from holiday and get the shed solar thing built and hooked up to this.

Almost snap.

I was surprised how much smaller the 100/20 charger is to the 150/35, so your 250/60 must be a beastly size.

I have them in a non recommended orientation but I air cool them with a low powered fan from below, they barely get warm.

I'll be interested to see if the bigger one gets warmer with the; as yet to be ordered; 575w panels, there will be a lot of juice going through them.