UK Only - Tesla Energy Plan/Octopus Energy

[JohnRatsey]

I'm happy that I didn't go ahead with this power plan. I had originally assumed that Tesla would tap into some solar generation forecasting to shift the solar export to the grid to later in the day and then, if necessary do some compensatory night time charging from the grid. The grid charging pattern reported by @Fred2 is similar to what I've been seeing (and not significant change in nearly 3 years). The off-peak charging is guided by the demand and the previous few day's solar generation. Tesla's software designers have evidently never experienced British weather to know that what happened yesterday is no guide as to what can be expected today. There's a seasonal range for the solar generation but, to get anything better it is necessary to interpret the weather forecast.

 

[Cuban8]

A simple minimum SoC at ‘x’ time would solve the problem. Yesterday, my panels generated 7kWhs from a starting SoC of 16% at 8am. The previous day’s generation was 16kWhs. This morning, I woke up to find a battery SoC of 30% with little forecast sun. I cannot see the battery getting us through the day. In fairness, this only happens after sunny days followed by bad days but for the sake of a slider in the App it is very annoying.

 

[JCUK]

I thought that charging and discharging would be controlled centrally by Octopus, it seems my optimism was misplaced.

My experience over the last 3 years is that the powerwall predicts solar generation based on the highest figure over the previous 3 days, and I have many examples which support this.

3 years ago I was informed by Tesla verbally that it predicted solar generation from local weather forecasts. I think this was an aspiration; and I have recently been informed by Tesla that they are still working on it, I am not optimistic.

 

[Dave101]

An update a few weeks in! I seem to be losing about 1.6Kw per day, consistently. Yesterday is a good example. I generated 27 and used 10.2 in the house leaving a net of 16.8. 23.8 went to the grid and 8.6 came back from the Grid a net of 15.2. So, my reckoning, 1.6 has got "lost" in the battery. I don't know if the battery started and ended the day at the same level. However, I have done the same calculation for the first 2 weeks of March and the days show 1.5, 1.6, 1.5, 1.7, 1.4, 1.8, 1.7, 1.4, 1.6, 1.6, 1.6, 1.5, 1.6. It is uncannily similar!

This suggests that I am "leaking" about 17.5p per day = about £65 per year.

My net export in this 14 day period is 34Kw, worth £3.80.

Whenever I look at the App during the day I seem to see random patterns of distribution of power is all directions!

I am beginning to wonder about the increased impact on the battery of power coming and and out so much more frequently.

Any observations?

 

[JohnRatsey]

See my reply to your other post on this subject in the SMETS meter thread.

When I prepared my own spreadsheet calculation of the costs and benefits of the Octopus Tesla energy plan I factored in my observed long term battery / gateway efficiency of 85% which might have been a little cautious as a higher daily power flow might, as your numbers suggest, increase the calculated efficiency if the overheads are approximately constant per day. It wasn't obvious to me where this loss was built in to the energy plan's bost-benefit estimator.

 

[Dave101]

Thanks John

The pattern is really consistent now, virtually everyday. The battery is charged up every day by a mix of solar and grid, the mix does not really matter. The battery then sits full for a while and is then discharged to about 19%. I am still losing 1.6KWH everyday.

One of my worries had been that there would be patterns of charge/discharge/recharge each day. This does happen occasionally for very small amounts, but is not a recurring pattern.

Therefore, from a battery life point of view, it seems to be getting fully charged each day and then discharged to 19%. Rinse and repeat.

Cheers

David

 

[Steerpike]

I have had a Powerwall for about 9 months and the average round trip efficiency for that period is 86.5%. The Powerwall is outside and the efficiency is slightly higher in the warmer months and a bit lower in the winter.

This ~15% loss was one of the things that put me off the TEP, other reasons were less control, loss of deemed export FIT, and concern about future changes to the rate.

 

[Dave101]

I have had a Powerwall for about 9 months and the average round trip efficiency for that period is 86.5%. The Powerwall is outside and the efficiency is slightly higher in the warmer months and a bit lower in the winter.

This ~15% loss was one of the things that put me off the TEP, other reasons were less control, loss of deemed export FIT, and concern about future changes to the rate.

Hi

Thanks fo this confirmation. The reason that I decided to go for TEP is that I have 2 arrays, so the difference between the income that I receive on the plan is much greater than I was getting through the deemed export amount. In reality, it looks like I am going to more than cover my gas bill through the income from TEP.

You are right about the loss of control, although we continue with the behaviours which we learned before switching to the rate.

Cheers