Tesla Powerwall 2 settings question - Tariffs and SEG with Octopus

Smccran

Hi all,
I've got a question about the Tesla Powerwall 2 settings.

I'm with Octopus, where its:
- 34p per Kwh during the day
- 12.1p per Kwh between 12:30am to 4:30am
- 4.2p per Kwh SEG, selling per Kwh back down the grid

So in the Powerwall 2 settings there are two modes.

Self Powered, which is supposed store PV energy until the battery is at 100% then push additional PV energy back down the grid.

Time-Based Control, which tells the Powerwall to read the tariff details that you have input (as above) to charge itself from the grid when the rate is cheap, and sell back if the rate is better.

I'm having to switch between these two modes at the beginning and end of each day, as, in Self Powered mode, the PW doesn't draw from the grid overnight, so does not top up in the cheaper window.

If I put the PW into Time-Based control, it charges to 100% overnight, at a cheap rate, but then when the PV system kicks in, it pushes that energy down the grid, even if the charge level is at a level lower than 100%. For example, at 8am the PW has used 20% of its stored energy, PV is generating, but the PW is pushing that down the grid, not charging to 100% first, then doing it.

Has anyone else got a similar setup, and has figured out how input tariffs that tell the PW to charge up in the cheaper window, but then use PV to hit 100% before sending it back down the grid?

Thanks
Shaun

[Deleted User]

The PW2 is doing what it is supposed to do. I am now on Octopus Flux with Time Based Control and 3 time periods. Each period has a cost and an export price. My PW2 charges between 2 and 5 am; discharges between 5am and 4pm (if there is no solar) and then exports Solar from 4 to 7pm whilst providing power for the home for the battery.

The PW2 looks at the predicted forecast solar and historical usage. If it doesn’t need to be at 100% SOC then it will set a lower limit. 

If you want to stop the PW2 doing something then the best way is to fiddle with the tariff settings in Time-Based Control.

StevieGal

Hi Shaun
Just found your post as was looking for an answer about adding an additional Powerwall.

I have the same set up as you and at the moment run in TOU mode and all works perfectly. Charges between 00.00 until 05.00 then tops up with solar during the day. As spring is approaching and hopefully more sunshine I don’t really want to send surplus energy back to the grid but would like to store it in an additional Powerwall but have yet to figure out the best way to do this so am looking into Self Powered mode but think this would require a lot more input from me.

MWT

StevieGal said:

I have the same set up as you and at the moment run in TOU mode and all works perfectly. Charges between 00.00 until 05.00 then tops up with solar during the day. As spring is approaching and hopefully more sunshine I don’t really want to send surplus energy back to the grid but would like to store it in an additional Powerwall but have yet to figure out the best way to do this so am looking into Self Powered mode but think this would require a lot more input from me.

As per my reply to your other thread, when you add a second PW you just end up with one larger PW, so don't think of it as two distinct units.

Right now with 2xPW2, on the recent decent sunny days, in TOU mode it charged up to around 60% over night and then exported most of the solar production during the day as it had worked out how much I needed to take me through to the low-rate at 23:30 (IOG).

StevieGal

Thanks MWT
Sorry for repeating myself after your initial reply but trying to get to grips with my Powerwall. I have had my Solar for 12 years so am on the max FIT payment but only had my Powerwall for 3 months so am trying to work out what works best for me, am having the 2nd Powerwall installed in the coming weeks. I didn’t realise the Powerwall was intelligent enough to work out my daily usage so only charges to a certain amount and then used my anticipated solar generation. I will have to do some serious reading and research. Thanks again for your reply.

AlThoros

Thanks for all your info as I too am trying to get to grips with my new PW2!
Essentially the same query - I would like my battery to charge on cheap rate overnight, use solar during the day and battery at night. 

My rates are 🐙 Econ 7 so
day 0730-0030 .27p
night 0030-0730 .11p
export .15p
Eventually got TBC to charge during the night to start the day with a full battery but what is happening after 0730 as solar is kicking in the system exports all the solar and uses the battery without topping it up so at the end of the day the battery is depleted to 50-60%
I thought the priority would be with solar House, battery, grid.
I have tried reducing the sell price as thought it might be thinking its better to sell at 15p and charge at 11p but that didn't work
Any suggestions to get the priority Im after. 

At present I am going self powered manually in the morning and back to TBC at dusk but Id rather it be automatic!
TIA 

AlThoros

“system exports all the solar and uses the battery without topping it up”

sorry to clarify - 100% of the solar goes to export and the battery powers the house.

MWT

AlThoros said:

“system exports all the solar and uses the battery without topping it up”

sorry to clarify - 100% of the solar goes to export and the battery powers the house.

If you have a sufficiently large battery to cover your house use during the high-rate period, isn't this what you would want to happen?

Using solar energy for the house saves you 11p/kWh, selling it gets you 15p/kWh...

If you really don't want that to happen then if you reduce the selling price significantly below 11p it should start to use it rather than export it... may not be immediate but give it an hour or two to adjust.