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Powerwall and Octopus Go experience?

gangzoom

Active Member
May 22, 2014
1,320
1,129
Uk
Finally got a date for our PowerWall install, 4th of November. Still a while away but cannot wait.

We are currently on E7 with Bulb, and have solar PV, but clearly in November sun will be limited.

I've seen lots of people have said the PowerWall software does its own thing with AI and not to micromanage.

Just wondered any real life owners have experience of using the PowerWall to maximise the crazy 5p per kWh Octopus offers for 4 hrs every night?

We only use 3-4kWh a day outside the car charging so potentially if we can get the Powerwall to charge at 5p per kWh thats very cheap electricity!!!

Though Bulb is only 8p per kWh, so absolute cost difference is tiny, still every bit helps :).

Or another general Powerwall advice/tips welcome!
 

Mark_T

Active Member
Nov 1, 2017
1,305
1,131
UK
There is a lot of good information over here that you might find useful:

Tesla Powerwall 2, one month in..... [Page 2]

I'm still researching the praticalities of the Powerwall, but at least we can now charge from the grid in the UK, so it does make sense to consider using the cheap off-peak from Octopus.

I've already moved to Octopus anyway (PM me if you want a referral code), smart meter should go in week after next.
 
Jul 5, 2019
176
133
Sussex, UK
If you have solar PV and a Tesla Powerwall can you charge the Powerwall from Solar PV during the day AND charge it using cheap night time electricity?
I've got the impression the Powerwall is either set up to charge from Solar OR from the grid.
Please can anybody with Powerwall and Solar PV tell me their experience.
 

Mark77a

Member
Jul 7, 2012
460
181
Poole, Dorset, UK
Screenshot_20200917-205031.png
If you have solar PV and a Tesla Powerwall can you charge the Powerwall from Solar PV during the day AND charge it using cheap night time electricity?
I've got the impression the Powerwall is either set up to charge from Solar OR from the grid.
Please can anybody with Powerwall and Solar PV tell me their experience.
Yes the PW can be charged from either PV's or Grid, and so good to charge at night from low cost rates (eg 5p /kWh Octopus go 12-30 to 4-40am) - or even they pay YOU to take energy (eg Octopus Agile when there is excess grid wind energy).
 
Jul 5, 2019
176
133
Sussex, UK
Thanks @Mark77a, very helpful. As I'm a newbie to this powerwall business I've annotated your graphs. Have I got it correct? Between about noon and 3pm a 3kW load appears, is this an immersion heater switching on when solar is above 3kW to heat your water? Can you tell me how many kW your solar system is?

Powerwall and Solar.png
 

Mark77a

Member
Jul 7, 2012
460
181
Poole, Dorset, UK
Thanks @Mark77a, very helpful. As I'm a newbie to this powerwall business I've annotated your graphs. Have I got it correct? Between about noon and 3pm a 3kW load appears, is this an immersion heater switching on when solar is above 3kW to heat your water? Can you tell me how many kW your solar system is?

View attachment 589409
Spot on except During the day I was also using the solar to charge an ev (although as you said this could be for heating water).
 

Mark77a

Member
Jul 7, 2012
460
181
Poole, Dorset, UK
The system is a nominal 4.2kW (14 x 300w panels with solar edge controller). South facing, on south coast it Gives up to 25 kWh on a sunny day in summer and up to 7kWh in winter. PowerWall is 13kWh.
 

tomorrowman

Member
Mar 10, 2020
296
273
Hampshire
Interesting. So even without solar a case could be made to install power wall and ensuring always use cheap off peak energy via a Octopus Go or Agile Tariff - Need to do the sums.

Is there ever a scenario where the car charger draws power from the power wall directly (I thought this was something to be avoided)
 
Jul 5, 2019
176
133
Sussex, UK
@Mark77a thanks for confirmation. Looks like a good system. Have you ever tried to work out the payback period? I assume it is more than a couple of decades, but good to know you are doing the right thing for the environment and a bit of techno fun too.
 

KennethS

Supporting Member
Supporting Member
May 3, 2019
517
359
UK
I'm looking at this very simplistically but payback period, in my mind, will depend primarily on a person's estimated annual electric use. Despite our best efforts, our house uses a substantial amount of electric and we can fully make use of a full Powerwall every day. So if I can use 13 kWh daily (essentially one full Powerwall) at 5p vs say 15p (the lowest all day tariff in my area) then that's £1.30 per day saved or £475 per year. Makes for a long payback but you also have to have a crystal ball to know where rates will be in 5, 10 and further years. I need more than 13kWh of cheaper energy daily, so went with the Tesla Energy Plan. At 8p per kWh 24/7 and no daily standing charge, it nearly halves my electric bill. Who knows how long that 8p rate will hold, but it makes the payback period for my Powerwall far easier to accept when I'm saving nearly 50% on a very large electric bill.
 
Jul 5, 2019
176
133
Sussex, UK
I assume the solar / powerwall system is also capable of exporting to the grid at peak times as a source of income. Charge at night with cheap electricity, charge some more with solar during the day, then sell some power to the grid during the evening peak.
Am I correct in thinking that the autobidder software is part of the system and could optimise income?
 
Jul 5, 2019
176
133
Sussex, UK
I'm looking at this very simplistically but payback period, in my mind, will depend primarily on a person's estimated annual electric use. Despite our best efforts, our house uses a substantial amount of electric and we can fully make use of a full Powerwall every day. So if I can use 13 kWh daily (essentially one full Powerwall) at 5p vs say 15p (the lowest all day tariff in my area) then that's £1.30 per day saved or £475 per year. Makes for a long payback but you also have to have a crystal ball to know where rates will be in 5, 10 and further years. I need more than 13kWh of cheaper energy daily, so went with the Tesla Energy Plan. At 8p per kWh 24/7 and no daily standing charge, it nearly halves my electric bill. Who knows how long that 8p rate will hold, but it makes the payback period for my Powerwall far easier to accept when I'm saving nearly 50% on a very large electric bill.

Wow, I did not even know that there was a Tesla Energy Plan. Thanks for telling me about it. So much to learn!
 

KennethS

Supporting Member
Supporting Member
May 3, 2019
517
359
UK
Wow, I did not even know that there was a Tesla Energy Plan. Thanks for telling me about it. So much to learn!
It's apparently not available everywhere and requires you to have 1. a Tesla. 2. some Solar PV (not clear to me how large a system, ours is 3.5 kW), and (iii) a Powerwall. As part of the process, having had solar and a Tesla, we had the Powerwall installed. Tesla threw in a free Tesla Wall Charger and 12 months of free electric capped at £500 (so in our case it will be £500 as a result of our high usage). The incentives took some of the sting from the Powerwall purchase. Not sure what the current offering is. With battery day around the corner I would likely wait to see what they announce if I were looking right now. But, with the Tesla Gateway now installed if there is some amazing new battery coming I may add it to my system down the line if the numbers make sense.
 

LukeUK

Member
Feb 25, 2020
394
236
Shropshire, UK
Makes for a long payback but you also have to have a crystal ball to know where rates will be in 5, 10 and further years.

Have you allowed anything for performance degradation over time, and expected lifetime, specifically outside of warranty?

My concern is that the kit just doesn't last long enough/well enough to pay for itself. A similar issue occurs with PV - the inverter dies outside of warranty and effectively re-sets the payback date by quite a period of time.
 
Jul 5, 2019
176
133
Sussex, UK
As part of the process, having had solar and a Tesla, we had the Powerwall installed. Tesla threw in a free Tesla Wall Charger and 12 months of free electric capped at £500
Always good if there are incentives. I can not find any at present, I just need to watch out for some future incentive to help ease the pain.
 

KennethS

Supporting Member
Supporting Member
May 3, 2019
517
359
UK
Have you allowed anything for performance degradation over time, and expected lifetime, specifically outside of warranty?

My concern is that the kit just doesn't last long enough/well enough to pay for itself. A similar issue occurs with PV - the inverter dies outside of warranty and effectively re-sets the payback date by quite a period of time.
Very valid concerns all. The warranty on the Powerwall being 10 years to 80% of original 13.5 capacity gives me a lot of comfort. In our case, my bigger worry is that the Tesla Energy Plan rate materially changes to a rate closer to the prevailing market rate for 24/7 power. Again in very crude maths terms, the current deal saves us £1,000 per year. So a payback period of less than 9 years. I recognise that within 10 years batteries will be cheaper and better, but as long as the Tesla Gateway (the computer brain behind the system, and it is quite clever) remains operating then adding or swapping battery should be a pretty straightforward affair. And with the Tesla Energy Plan there is nothing contingent on my Solar PV performance. I installed the Solar in 2011 and the return on investment has exceeded my expectations and it continues to perform well. A replacement inverter is inevitable, but budgeted for out of the FIT anyway. The Powerwall for us was an entirely separate consideration and the existence of the Tesla Energy Plan (and to a small degree the incentives given by Tesla for signing up early this summer) put us over the edge to go ahead.
 
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roadcred

Member
Aug 23, 2019
184
96
UK
I have 7kW of Solar and a Powerwall 2. Stayed on Octopus Go for a month nthen moved to Agile. Problem is still got the standing charge but hopefully will solve that by moving to TEsla Energy Plan. Slight problem I am currently between Teslas.
I have found the savings really racked up with my Powerwall. Will get a second one when I can afford it. Its not just about cost its also about energy security.
 

Dilly

Active Member
Feb 24, 2020
2,051
1,666
Norfolk
I have 2 Powerwalls and 11Kw PV.
With the right settings in place (by the PW installer) I draw about 180Wh a day which is just over a kilowatt a week from the grid during the spring and summer quarters. That’s mainly the PW’s balancing against the grid.
I also charge the M3, an Outlander and the PW’s from solar during these quarters as well as heating water.
In late autumn I’ll switch the Powerwalls from self powered to balanced and then later to cost saving using off-peak Octopus Go to top up the cars and PW’s.
The advantage of having two PW’s allows me to draw 10Kw and charge at 10Kw minimising any likely grid draw. All my winter power is cheap rate or a small amount of solar.
I only got the M3 in March so have no winter fuel costs. But it’s cost me a penny for nearly 1400 miles so far.
My previous EV, an Ioniq did 5500 miles over 18 months at a cost of £71

There no real payback but a lot of satisfaction and of course I haven’t suffered any effects from the 21 power cuts we’ve had!
 
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Fred2

Member
Sep 12, 2019
68
57
Uk
Makes for a long payback but you also have to have a crystal ball to know where rates will be in 5, 10 and further years.

if you want to refine your crystal ball there is historic data from the ONS on consumer electricity prices. I’ve no idea how they account for variations between providers but their index is currently at 160 (their basis point of 100 is 2010). Last 25 years or so of data is here: https://assets.publishing.service.g...ds/attachment_data/file/912024/table_213.xlsx

over the past 10 years that’s an average of nearly 5% increase per year, which is much beyond expected performance degradation of panels or battery
 

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