MrTWales

Ah thanks for this. I wasn't aware of this - I thought that you could have Flux Export only with Flux Import, but I wasn't aware of any other options. When I can face it I'll think it through and get it sorted. My inverter has a fair number of options but not quite as many as I'd like, but I can set several windows to imports / push to the grid.

I'm one day shy of a full year with panels and it's amazing how generation varies. Not just by month but by day. I know it's kind of obvious but one day can be three times the previous day very easily. My system is 12*410w panels at only 10 degrees on a flat roof, so bad for winter but it was an easy install and I can clean myself etc. The chart shows the amazing May and crappy July/August that we had!

Oww...I'm on Flux but it looks like I should be thinking about Cosy. What I'm worried about is judging how much to charge the battery. If it gets full in the day then I'm at least getting an export amount paid now, but this stops with Cosy? I guess it's less of an issue each day and you can top up to a certain figure before the high import rates start.

As others have said, shading is a big issue potentially and another is weight. The usual fitting method with a flat roof I believe is ballast, so they add concrete to the fixing brackets. With the panels maybe being 20kg each that's a lot of weight so the rafters need to be strong enough.

No worries - at the moment my usage charge is a decent credit, but in the winter I may be better off with a different tariff. I suspect the best ones for those with a decent sized battery will require an EV.

What are the export rates? I don't have an EV so I'm not sure it's an option for me though anyway.

Well, being on this tariff certainly makes things interesting. As far as I can see I can't change the priority discharge ordering in the inverter settings (to using the battery first) in the evening Flux period of 4pm to 7pm, but I can force a battery discharge. But if I discharge at 25% say, which is 1kw in my case, then it just pushes this much out and won't increase if the load is higher. If I discharge at 100% then the export is 4kw + solar - useage, which can be loads. The downside is potentially depleting the battery and having to import at the highest rate. It seems to me that the best solution is to ignore the first part of the Flux period and set the discharge from something like 6pm to be 100% with a cut off whereby the battery doesn't get below a certain point. The latter is just because it may mean importing at the heighest rate if the battery runs out, but not leaving much battery at 7pm isn't a disaster as the Flux export rate is probably very close to the standard import once effeciency has been factored in. There then is the Flux period from 2am to 5am. After efficiency it seems like importing then and exporting at the standard rate is virtually break even, maybe a tiny gain. So there is probably merit to just fully charging the battery in this period. I think I'll not bother recharging when the weather is good as the battery will get to 100% before 4pm on most summer days, but otherwise charge to a specific percentage figure.

I take there is no gas installed? If so and you can get on something like the Octopus Flux tariff then it's cheaper to use gas for water than to reduce the export. Fwiw I had a water diverter installed way after the main installation (they just ran out of time on the day) and it was maybe 90 mins or so to install if not less when they finally came back. It looked simple for any electrician to be honest.

Just to update this - I am now on the Flux Export Tariff. For anyone doing through this process, it's worth calling Octopus if there are any delays. Eg the MSC cert had the wrong MPAN code so I had to get the installer to change this and send it on (it wasn't their fault fwiw), and when I called Octopus after a few days to make sure they had it it was just sat there but the moment I called it got forwarded on. Also, when the export was set up it it showed incorrectly in the app (as if it was an import on the variable tariff) but a quick call got it flagged correctly. So now I can see that I exported 19.1 kWh yesterday (being on holiday now!), compared to 19.4 kWh as per the inverter app. So that seems pretty good, with £3.93 credit.

I think my smart meter is different, it just has up and down buttons. I've checked the G99 letter and it mentions something or other about max export but doesn't have any reference to a MPAN so I guess I'll have to wait. Mind you, the weather forecase is pretty crappy so at least I can use any excess for the water.

Thanks, looks like 10-14 days and I better put the immersion diverter back on!

Edit - I think I'm on Flux Import so I can't export yet, I assume anyway. Hopefully not for long!

Update - I am on Flux! I won't break open any champagne until I see exports working (I can't see how this shows in the app) but the process was very quick. I had a smart meter install on Wednesday (via Shell, or a contracttor should I say) I called Octopus on Thursday to switch. They said I'd be on the variable tarrif (which was the same rates as Shell, but for the standing charge which is a bit lower) and needed to apply to Flux, but it could take 6 weeks as they need to test that they could communicate with the smart meter etc. I applied on Friday for Flux, which meant ticking some boxes and providing a G99 letter (to show DNO approval) and the MCS cert number (which they look up and tie to the property). Now, two says later, they say that I'm Flux. So, I'm very impressed so far - even without being on Flux the app is very good, with usage data easily seen for electric and gas. Fingers crossed that the export works properly.

This is what I've just got from Shell. I guess there is some change in wholesale costs or something from 1 July. Your electricity rates are changing from 33.282p to 30.222p per kWh. Your electricity standing charge per day will remain the same at 53.82p. Your gas rates are changing from 10.467p per kWh to 7.664p per kWh. Your gas standing charge per day will remain the same at 29.11p.

This is why phrases like "utility" are used when trying to model decisions etc. Most people would rather £1m with certainty than £2.1m with probability 50%, as this would likely maximise their happiness even though the decision to take the £1m loses £50k in value. My 65 inch TV absolutely pays for itself in happiness units, as does the doughnut I'm about to eat!