@bontwoody Obviously I’m not Andris but that sort of thing has never stopped me from sticking my oar in if you don’t mind.

My installers were very reluctant (In 2021 when I first started researching my proposed plans) to even suggest I should have one Powerwall - never mind the two I enquired about; ‘Nah, the ROI on one is doubtful - never mind two, you would need far more PV production than you propose.’ [8.1kWp.] Then of course, the price of energy climbed vertically and all bets are off! In addition, the Octopus Energy Agile tariff was introduced enabling very useful 30 minute low-demand-thus-cheap periods enabling economic and convenient charging times.

When I had the ASHP installed, the electricity consumption increased as I knew it would when I originally enquired about having 27 kWh of Powerwall to provide a ‘buffer’ (the best type of buffer😉). My PV insttaller did not market heat pumps and did not seem very interested in seeing my views on planning ahead.

With 27kW/h of storage, I now only charge for sufficient hours to keep the battery topped up at the greenest half hours and rarely need to pay more than 14 pence per kW/h but usually much less. I am also able to export from the battery during ‘Saving Sessions’ which helps the grid and my bank balance! The previous set up I used with OE was with Cosy tariff which allowed a total of six hours at their ‘Cosy’ rate but this was still approx. 17 pence per kW/h; outside of the Cosy hours, a rather higher rate applied.

The MyEnergi Eddi is programmed to heat the water during the early hours coinciding with the cheapest and greenest rates too.

Our cooking is all electric and the timing is no problem as the battery supplies all we need during any peak time cooking.

Agile works for me and I tend to export as much of my PV energy as I am able as the return is good at 15 pence per kW/h; sell high - buy cheap!😉

Regards, Toodles.

@toodles Thanks toodles, does the import/export require a reasonable investment of time? I ask because I cant see my brother in law doing that. I would :-). Have you calculated the time period to see your ROI yet?

@bontwoody yes th

• Yes, the heating is never on at that time, but our house is a new build so the heating during the night is plenty for the whole day. It is never on during the day, and the lowest I have seen the temperature go was 21c if the house goes below 22.5c the heating kicks in but only beetwen 10:30-6am.
• I use a programable thermostat with weather compensation.

@andris Thanks 🙂

@bontwoody I decided that the ROI is just a concept when it comes to comparing this to the lack of a crystal ball to foresee the energy prices for the next 10 years but I think 10-12 years should see me on the gain side! I was given to understand 7-8 years at higher prices ought to cover the cost from the savings - so I am being a little pessimistic by planning on 10-12 years.

As to the ‘faff factor’ I spend about 5-10 minutes (I am retired!) checking the Octopus rates (via Octopus Watch) and tapping these into my Tesla app. My water heating stays the same day to day unless I see a plunge price and I’ll intervene to include this and if necessary, prevent the pre-programmed time from charging the Sunamp Thermino before we get to the plunge price times. 

My Tesla kit is set to allow me to toggle ‘everything’ as an export option and this I have done during ‘Saving Sessions’, I just need to remember to toggle the option off again after the session finishes. I have wondered if there might be a programming option for this one day but I haven’t seen anything yet. I understand that OE are considering the use of the API to connect various storage systems up for virtual battery systems but as yet, I have not seen anything in the offing for Tesla Powerwalls.

Regards, Toodles.

@toodles Thanks 🙂

Just had my latest bill and statement in from Octopus, excluding the period 12/01/24-10/02/24 when my smart meter had some communication issues. (That's another debacle but I won't bore you with it) On Cosy, my average kWh cost excl. VAT & standing charge was 17.41p. On Agile it is 12.66p. That's a big 27% saving. Well worth switching 🙂 

@allyfish Aligns with my thoughts entirely! Toodles

@allyfish that is back to pre energy crisis prices 😀!

I've just looked back on my bill for 15 Feb - 8 March and I was charged 14.05p/kWh +VAT.  I can't understand these people who insist they won't have a smart meter then complain about the price of energy and 'huge profits'.

Posted by: @ianmk13

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I can't understand these people who insist they won't have a smart meter then complain about the price of energy and 'huge profits'

That'll be my in-laws. They have a small second home nearby, which they have a pre-payment meter in. The previous owner was on pre-payment. They've had it 8 years, and refuse in principal to get a smart meter, so keep the pre-payment one. Madness! How many hundreds of pounds they must have overpaid in that time....