• I have been receiving invitations from Octopus Energy to use ‘Free Electricity’ on some afternoons when the wind doth blow and an hour’s ‘free above your normal usage’ energy offer is made. I have endeavoured to employ my degree in Scroogenomics and arrange for the Powerwall to need charging, the Sunamp Thermino to need some charge plus various domestic appliances to run during the hour, (on one occasion, 2 hour period). Even the kettle has been poised ready for switch on and today, even the heat pump was given its’ head for an hour.
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• Wuddn’t you know it, during the preceding hours, there were numerous clouds and little solar energy to be harvested but, come the hour, the sun is bright, the air is cool and we have near record solar production! We did manage to extract about 10 kWh for free but the solar panels supplied about 6 kWh during that hour.
  

  

  Well I can only think that S*d was a busy boy writing all those Laws! Regards, Toodles.

@toodles this is another advantage of being on IOF. When there is a 'free electricity' hour, if you are on IOF then Octopus will credit you with a 'free hour of charging' in addition to any additional electricity usage. I'm not exactly sure what a credit for a 'free hour of charging' is, but I think it's 80% of my battery capacity (charging from 20% to 100%) at the day rate, so 10.8kWh x 22.36p = £2.41, plus any additional electricity I actually use for charging the battery etc. I've received amounts varying between £2.41 up to £2.93 for these sessions, so very happy with that given we've done nothing differently to our normal usage. As you have two powerwalls, I think you'd get a minimum of £4.82 per session in addition to any extra electricity used.

@old_scientist If IOF is still running next late spring / early summer…😉 Toodles.

@toodles Fun fact the free electricity session is technically not (quite) free (but very low cost) as the Vat on the energy is not reclaimed - effectively meaning you pay 5% of the average rate rather than nothing. So a 30p/pkwh daytime rate would cost 1.5p/pkwh. 

If you use 30p for 1 kwh this gets added to your bill then you get charged 5% on top of this in Vat (31.5p).

Then octopus refunds the 30p, but the 1.5p vat does not get refunded. 

@andrew-j-h There are two things in life that are certain and invariable… Death (eventually) and Energy Taxes (Immediately!) Toodles.

The new rate for OE’s Cosy Tariff from October suggests to me that I’ll be making an adjustment on my Tesla app so that I’ll use as much of the produced solar energy as my system allows - any advantage of ‘arbitrage’* has now vanished. I endeavour to only import during the cheapest 8 hours per day and run on battery for the other (more expensive) 16 hours. The new rate (inc. VAT will be 14.596 pence and as the ‘Outgoing’ rate is 15.0 pence, charging the battery from solar is going to be the better (cheaper) option for me; 14.596 pence per kWh plus the 10-15% losses in conversion suggests that exporting any energy that could be used is pointless now.

*Arbitrage was very marginal at the lower rate!

Regards, Toodles.

Our region has increased to 14.794p which is a 14.6% increase, notified in a letter from Octopus that states "Energy prices will rise 1-2% for most homes from October-December". Still it's significantly less that the ~26p I received for export on IOF over the summer so there is still good leverage there, and it is that credit built up over the summer that will be paying the bills in winter.

As you say the optimum strategy seems to be to pull from the grid during cheap periods (which means by definition we are not exporting), and to self consume solar at all other times rather than exporting it as charging the battery from the grid will now cost more than 15p after losses are considered.

I'm considering if Agile is worth a gamble for October/November, where there is still some solar generation and one may well be able to achieve a net import price below 15p as there only need to be a few cheap slots (below 15p) each day to top up the battery. My usage was around 20kWh/day, so with 13.5kWh battery, some solar generation and some cheap slots, I think I could manage on Agile until the really cold weather hits in December.

I am on Octopus Intelligent @ 6.67p on the overnight rate. I have 18.8kw batteries (no solar) so will be interesting to see how much of my winter usage I can do at the cheap 6.67p rate or how often they run out and I will have to use the peak rate. 

The current rates are fixed until end of June 2026. 

Off Peak Rate - 6.67p - 23:30 - 5:30

Peak Rate - 28.25p - 5:30 - 23:30

I have a Heat Pump, so on the Cosy Tariff I get 7h at 12p, 3h at 36p and the rest at 24p.

i have 5kW off batteries and Solar, from April to November I am self sufficient, the only challenge is the max draw off the batteries is 3kW/h so if you can only use 1 high power appliance, either cooking or washing, without the inverter maxing out.

The Washing Machine and Tumble Dryer are Ultra efficient with energy, with a Heat Pump Dryer using 600W instead of old types at 2.3kW

Octopus breakdown the energy usage for the 3 charge rates, since April, I’ve managed to get 95%+ off my energy at the cheap rate; Solar during day and Batteries for evenings or when a cloud goes over!

@agentgeorge Come the Ist of October, the Cosy cheapest 8 hours per day will cost a fair % more; in SE England, I’ll be paying 14.596 inc. Vat per kWh.☹️ Toodles.

Reminder for anyone with batteries, with prices going up tomorrow, today would be a good time to fill those batteries to 100% before tomorrow's increases.

Ideal for Cosy users with that cheap rate slot 10pm to midnight 😀 

@toodles ive just accepted cosy fixed as its cost saving in the midlands