@peterackstraw A few observations rather than a recommendation for a particular tariff. As you are using a Tesla PW2, I would assume you may have had this installed before last winter commenced. My sunny day solar production is twice yours and my average winter day production is perhaps ~10 - 12% of this. This suggests that your Outgoing returns are not going to amount to much in the winter months so possibly of minor consideration. I don’t have EV charging rates so have stuck with Cosy for importing from the grid. I have 27 kWh of PW2 and use just the cheapest 8 hours of each day to charge the PW’s and this is sufficient to power everything including an 8 kW Daikin heat pump. Some readers are using the Agile tariff and this probably works best if you have smart control over the charging and heat pump. I am unsure whether any EV tariff is able to provide sufficient charge time so that with a large enough battery, there would be little or no need to use the more expensive periods; perhaps users of EV tariffs could advise here.

Of course there is still a great need for a crystal ball to determine what tariffs and deals might be in operation in 3 - 6 months time. There seems to be a lot of possible changes in the offing - not helped by the geopolitical situation of course.

I’m sorry if this is not of much help, but I hope it may have provided food for thought nevertheless. Regards, Toodles.

@toodles may thanks. My solar was fitted 7 years ago. 23 kw at best per day. A bit disappointed with that.

Regards Pete 

Inteligent octopus go. 

So charge battery over night at 7p.

Then get paid 12p per kW for all solar produced on any given day. This is with outgoing octopus. 

@peterackstraw 13.5 kWh’s of battery capacity is unlikely to ‘see the day out’ even with any solar energy contribution. Once the battery and solar contribution run out, what will the EV tariff’s daytime rate be? At least with Cosy, there are three ‘chances’ each day to top up the battery. This means there are eight hours per day when the house consumption would be supplied at the lowest Cosy rate and the PW2 could be topped up. During those remaining 16 hours, battery and any solar available would be used to try and avoid using grid energy at higher rates. That’s how I see it anyway. Regards, Toodles.

Many thanks. Good info 

@peterackstraw What's the calculated heat loss for your property? Ours is a relatively new build with a heat loss of about 6 kW for approx 200 sqm house in the South East. We were on the Cosy tariff, but switched to Octopus Go when we doubled the battery capacity to 13 kWh. Surprisingly, now Go is comparable to Cosy other than probably January, and from March to October, it's much cheaper than Cosy. With one hour extra on Intelligent Octopus Go, it might be a good tariff to be on. But the 12 kW heat pump might tip in favour of Cosy. Try out the tariff comparison tool on Tim and Kat's Green Walk website, if you haven't tried that already.

@chandykris

Thank you this is really helpful info. I will look into this. Regards Pete 

@peterackstraw as others have said, it's going to depend on usage. For reference, we have a PW3 (13.5kWh), and on the coldest day in winter our total house usage is around 45kWh which we are able to completely cover from the Cosy cheap rate periods. Besides being nicely spread out during the day (never more than 6h between cheap rate periods), they also fall at reasonable times for heat pump usage directly from the grid whereas we tend to set back (or even turn off) the heating overnight when Intelligent Go is cheapest.

Until you've had your heat pump for one complete winter it's difficult to say whether Cosy or Go would be cheaper, and you are probably only looking at the 3 coldest months of Dec-Feb for Cosy. As @chandykris suggests, I'd also suggest having a play with the excellent tariff comparison tool on Tim and Kat's Green Walk website. If you have relatively accurate numbers to what your usage may be it should be able to give you a reasonable answer. Maybe you can estimate your ASHP usage from looking at smart meter gas usage from last winter, assume efficiency of the old boiler and then assume a COP of 3 in winter to give you a ballpark estimate for the equivalent electrical usage, and you won't be too far out.

Hi and thanks for the info. 

Maybe cosy in the coldest months and intelligent go for all other months. 

Regards Pete 

Posted by: @peterackstraw

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Hi and thanks for the info. 

Maybe cosy in the coldest months and intelligent go for all other months. 

Regards Pete 

That's what I do - Cosy in the winter and (intelligent) Flux in the summer as I don't have an EV.

Whether you can make an EV tariff work for you in winter will really depend on the size of battery (and solar, which can still make a useful contribution in winter) and heat loss of the property.

The downside of Cosy, which will be a factor for you, is you'll be paying more to charge the car versus Intelligent Go, so you also need to factor in that which will swing things back towards the EV tariff. There really is no one-size-fits-all answer, and very much depends on your own individual usage.

Great info. Thank you. 

Regards Pete 

@papahuhu the numbers are in for Flux for July, and it's been quite the month.

My net income (excluding standing charges) on Flux is around 170% of what I would have generated if I'd just self-consumed and exported the excess as SEG at 12p/kWh

My average import and export prices were actually very similar. My average import price was around 20.8p and average export price 20.6p. The average export price was dragged down due to the exceptionally sunny weather, hence more exported at the lower day rate of 10.2p than otherwise might have been expected, so normally I would expect to achieve a slightly higher export price which would be useful in helping to offset any conversion losses.

My strategy was to fully export the battery every evening peak (4-7pm) and then draw house load from the grid. We prioritised as much usage as possible from excess daytime solar rather than export at 10.2p/kWh. The battery added minimal charge at the end of the cheap rate overnight period (2-5am), just enough to see us through our background load until the sun came up at 6:30am. Sometimes it wasn't quite enough, so if I woke early, I was manually making sure there was 5% in the battery. The Tesla AI did a rubbish job of predicting days where there wasn't enough sun to charge the battery - one day the battery only charged to 40% and another only 50%. If I had automation, I would have set it to manually charge to 50% overnight knowing the weather forecast looked poor the following day. However, most days were sunny and the battery was typically full by lunchtime.

In the absence of IOF, regular Flux has been OK and the best summertime tariff currently available, for me at least.