I am in the same position and of the same opinion - stick or jump?! Quandarous, Toodles.

Interesting, but IOF is so much better for us in summer, I will need to calculate if the saving would offset the £25 early exit fee to switch in spring.

It looks like a no-brainer to accept the Cosy Octopus Fixed rates as they are "only" 10% higher than the existing rates rather than 14.6% higher! I'm fortunate to be able to virtually always only use the off-peak rate as I over-sourced my battery capacity on the assumption of using Agile rather than Cosy. I can easily get through the day only using live and stored off-peak power. I don't think I'll ever go back to the tyranny that is Agile. Too many crazy-price days and too much messing about. On a related topic, only this week I replaced an old gas hob with a brand new one (heresy, I know). This was despite really wanting to go down the induction route. The reason? Purely based on the DNO only allowing a 7kW inverter rather than the 12kW I wanted. The difference meant that an induction hob would have regularly tripped us over into peak energy usage. What planet was the DNO living on when refusing a larger inverter for a customer with a large battery bank? Did they think I was ever going to use it to suck-up peak rate electricity and overload the local supply? Something needs to change at SP Energy Networks.    

Posted by: @howardp99

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It looks like a no-brainer to accept the Cosy Octopus Fixed rates as they are "only" 10% higher than the existing rates rather than 14.6% higher! I'm fortunate to be able to virtually always only use the off-peak rate as I over-sourced my battery capacity on the assumption of using Agile rather than Cosy. I can easily get through the day only using live and stored off-peak power. I don't think I'll ever go back to the tyranny that is Agile. Too many crazy-price days and too much messing about. On a related topic, only this week I replaced an old gas hob with a brand new one (heresy, I know). This was despite really wanting to go down the induction route. The reason? Purely based on the DNO only allowing a 7kW inverter rather than the 12kW I wanted. The difference meant that an induction hob would have regularly tripped us over into peak energy usage. What planet was the DNO living on when refusing a larger inverter for a customer with a large battery bank? Did they think I was ever going to use it to suck-up peak rate electricity and overload the local supply? Something needs to change at SP Energy Networks.    

Interesting Howard about Agile, I've never been on it but I suspected that it might be as you describe. Atm I get by using off-peak power, saving high load for those periods, and when it's colder turning the heat pump up in the off peak to get us through the peak, it's only when it's very very cold that it uses all of the battery storage. We too cook with gas, only due to us not being able to afford to have a new kitchen since we moved in, but once we do we'll be going electric. Given how well the current system has performed, I'm hoping to add more panels as I still have space and also get a higher capacity inverter and more battery storage so that we can cook and have the heat pump on at the same time in the peak period on those cold days.

Yes I find DNO's in general to be short sighted, I suspect it may be because they don't have the capacity in the network for large amounts of exported electricity when it's sunny.

@trbob Hi, it was not the export aspect that limited the inverter to 7kW. The export side was capped at 4kW due to the concern about local voltage exceeding the 253V maximum allowed. So, I accepted the 4kW export limit, and this is done on a 7kW inverted by a password protected setting. My solar is 4.2kWp on a SW and S arrays and so is incapable of exceeding 4kW at any time even on the best sunny day of the year so that was not an issue. The problem was that by limiting the import to 7kW it also meant that I could not self-distribute within my own home more than 7kW of stored battery power. So, I am now stuck with gas for the next 15 years.

@trbob Agile last winter was a disaster. The previous winters it was pretty good. A lot of folk tried to defend Octopus over the Agile pricing saying that the algorithm was transparent and nothing had changed. I think the truth was that Octopus chose to become very predatory over their peak pricing and hiked the maximum up to £1/kWh which was a tad cheeky. There was also some very dodgy practices in the auction market for electricity supply with generators sitting on their hands and choosing not to supply, which is their prerogative, I guess. It's also interesting to see there is now a £25 early exit fee on the fixed Cosy deal. I have never switched between Cosy and Agile, back and forth. I was simply on Agile for a couple of good years and moved to Cosy last February when I really couldn't make Agile work despite juggling the best time to charge day-in and day-out. Life is so much simpler on Cosy. I also export when I have spare solar capacity and time this between 16:00 and 19:00 to maximise the return.  The best rate is normally a few pence more than the Cosy cheap rate so if I over-export one day and need to use the off-peak Cosy the next day it's not a disaster, but there's no point buying on Cosy to re-export, unlike on a good Agile day. Just be careful when adding more solar panels. You may need or benefit from having Tigo optimisers fitted. I have two arrays, 4-off West-facing and 6-off South-facing, but when I went from a 3.6kW inverter to a 7kW inverter the 4-panel array was inadequate in voltage to activate the inverter and so they had to be wired as one array with all 10 panels fitted with optimisers. The cost of this fell to the installer as it was their fault in not realising this limitation. The cost of the optimisers (about £400 plus scaffolding charges) would have made a big dent in the economics.

Posted by: @old_scientist

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Interesting, but IOF is so much better for us in summer, I will need to calculate if the saving would offset the £25 early exit fee to switch in spring.

For our usage, I estimate I may save around £12 during the winter months for Fixed Cosy vs the Cosy Oct 2025 pricing, so not enough of a saving to cover the £25 early exit fee (assuming the Oct 2025 pricing does not change significantly in Jan 2026).

In my opinion, Agile works best in Spring and Autumn, where the weather is a little unpredictable and our usage is a little lower plus there is still a significant solar contribution. This means we can largely cover usage from solar plus a small top up from any cheap Agile slots on more expensive days, but can export the battery to fully benefit from any plunge pricing. High usage months (Dec-Feb) are just too risky unless you have a very large battery.

I've singed up to the fixed Cosy Octopus tariff. The fixed 12month rate is currently slightly cheaper than the October 2025 Cosy price rise rate. it's going to save me £8 over 12 months according to my calculations! 😉 Wholesale prices 'may' fall in 2026, but there's a lot of uncertainty still in the energy market and geo-political uncertainty as well. The UK's electricity generation will still be heavily reliant on imported natural gas to power it for many years to come and interconnect imports from Europe. The UK offshore wind industry development has slowed to a crawl, and new nuclear capacity is at least 5-10 years down the line.

@allyfish I'm somewhat surprised the saving you have worked out is only £8/year. Not wishing to pry, but that suggests your current annual cost excluding SC is only around £200. That would be for where I liver where the fixed Cosy rate is about 4% less than the new flexible rate (and 10% more than the old Cosy rate). So, an £8 annual saving therefore implies around a £200/year bill. My annual usage is around £1000 so I should save about £40/year on fixed Cosy, which is why I have fixed.

@howardp99 As I am still contemplating a summertime flirt with IOF next year, I am still dithering as to whether I could save the £25 termination fee or not (~6,000 kWh. for Nov. ‘24 to end of March ‘25) Must ‘do the math’ later to see. Regards, Toodles.

@howardp99 it might have saved me £8 compared to the price rise details announced 20th Sept. I didn't updated my spreadsheet with those. Were an all-electric house importing around 7000kWh a year. 88% of that is at Cosy low rate due to BESS and scheduled charging when we're importing. I currently pay £1200 a year or thereabouts, £100 a month DD. I calculate our average cost per kWh will be around 18.6p incl. standing charge. Fixed rates for our area: Oct 2025: day 27.46, low 13.47, peak 41.19, SC 58.21/day incl. VAT