Cost savings more vs saving my powerwalls lifespan

[LadyLion]

I read an article that suggested not using cost saving in the wintertime because the rate differential is small with TOU A for example with PGE and it is better to pay more for winter utility and preserve the life expectancy of your PWs.

is this a legitimate consideration when choosing your selection of Tesla energy app plan as well.as selecting your PGE TOU A, B, or EV (even if you don't have an EV as I don't YET)?

 

[cwied]

Yes, depending on the differential. Given the 10% round-trip loss on energy flowing through the Powerwall, it is a no-brainer to switch to backup-only if the difference in peak and off-peak rates is 10% or less. That's the case for me on the winter E-6 rate. However, when I switch to EV2-A, I will be on cost saving year-round since peak is 2x off-peak even in the winter.

Given the impact on the Powerwalls, the actual breakpoint for the decision is probably a little higher than 10%, but I don't think anyone has the data to do a quantitative calculation on the exact point at which you'd be indifferent to using the Powerwalls or not. The lifespan of Powerwalls is a big unknown right now.

 

[jjrandorin]

The only thing we know about lifespan, is that they are warrantied to have 70% of their capacity remaining at the year 10 mark, if charged from solar.

Its a gamble, for sure. I am using self powered mode, so I am charging and discharging them daily. in the summer time from 100% to about 25% (my reserve) and right now from 100% to 40% (my reserve). This is a highly personal choice, I think, but i am somewhat gambling that either everything will be fine long term, OR that constantly cycling them causes more than 70% degradation at the 10 year mark.

I am also enjoying pulling as little energy as possible from the grid, in general, so there is some self satisfaction on my part to that, as well.

 

[MJ_CA_2019]

The only thing we know about lifespan, is that they are warrantied to have 70% of their capacity remaining at the year 10 mark, if charged from solar.

And to this point, if cycling it daily causes it to be lower than 70% at the 10 year mark (or another relative point in the lifespan) wouldn't that trigger some cure from Tesla? I personally wouldn't stop myself from getting the maximum benefit from my item to prevent the warranty from kicking in... quite the opposite actually.

 

[wjgjr]

And to this point, if cycling it daily causes it to be lower than 70% at the 10 year mark (or another relative point in the lifespan) wouldn't that trigger some cure from Tesla? I personally wouldn't stop myself from getting the maximum benefit from my item to prevent the warranty from kicking in... quite the opposite actually.

I think the issue is there are a range of possibilities. For example, it could be that using cost savings causes it to hit 70% at 10 years, versus 90% for backup-only. In that example, there is a net negative to cost savings of 20% of capacity, and possibly an indication of overall shorter usable lifespan of the PW. (And to be clear, that doesn't mean it is wrong to use cost savings, just that there is a negative to factor in.) But, it might be 60% vs 80%, in which case, yes, you can claim the warranty and might even come out ahead (depending on the condition of the replacement, which might be used.) And it is also possible that cost savings doesn't actually affect the loss, so it comes out at 80% (or some other number) for both.

And it is likely both that it will be somewhere in the middle and it will depend on the specific install (including some luck as well as the exact usage patterns and the environment of the batteries.) That is where it becomes a bit of a guess/gamble if the specific goal is to maximize savings in situations where there is an opportunity to take advantage of TOU rates.

 

[jjrandorin]

I think the issue is there are a range of possibilities. For example, it could be that using cost savings causes it to hit 70% at 10 years, versus 90% for backup-only. In that example, there is a net negative to cost savings of 20% of capacity, and possibly an indication of overall shorter usable lifespan of the PW. (And to be clear, that doesn't mean it is wrong to use cost savings, just that there is a negative to factor in.) But, it might be 60% vs 80%, in which case, yes, you can claim the warranty and might even come out ahead (depending on the condition of the replacement, which might be used.) And it is also possible that cost savings doesn't actually affect the loss, so it comes out at 80% (or some other number) for both.

And it is likely both that it will be somewhere in the middle and it will depend on the specific install (including some luck as well as the exact usage patterns and the environment of the batteries.) That is where it becomes a bit of a guess/gamble if the specific goal is to maximize savings in situations where there is an opportunity to take advantage of TOU rates.

Yeah this is where I am on it. Its a gamble, but I figure I will just use it to reduce power I pull from the grid, because that makes me feel good. SCE is not "quite" as bad as PGE, and I dont dislike SCE as much as many up in PGE land dislike them (@holeydonut @Merrill @RKCRLR et al.) but.. I dont "love" them either, and the less I pull from the grid, the better it makes me feel.

 

[Merrill]

Yeah this is where I am on it. Its a gamble, but I figure I will just use it to reduce power I pull from the grid, because that makes me feel good. SCE is not "quite" as bad as PGE, and I dont dislike SCE as much as many up in PGE land dislike them (@holeydonut @Merrill @RKCRLR et al.) but.. I dont "love" them either, and the less I pull from the grid, the better it makes me feel.

You need to watch Power Trip on independent lens, very informative.

 

[holeydonut]

You need to watch Power Trip on independent lens, very informative.

You know, everyone keeps telling me to watch that. But it doesn't show up when I search for it on AT&T UVerse.

But my wife says I shouldn't watch it since it'd just make me hate PG&E more.

 

[jboy210]

I was originally concerned about the Powerwall lifespan. But with the announcement of new cells on Battery Day I am less concerned. I imagine if I replace my V2 PWs in 10 years I will be able to get much higher capacity for the same amount of money and similar size from a V3 or V4 product.

 

[Merrill]

You know, everyone keeps telling me to watch that. But it doesn't show up when I search for it on AT&T UVerse.

But my wife says I shouldn't watch it since it'd just make me hate PG&E more.

It is on PBS in the Bay Area channel 9 and 54, you can go to independent lens and look up the local channels. You wife is correct. Also if you cannot find it on tv you can watch it on your computer thru the video on the independent lens web site.

 

[bob_p]

Assuming PowerWalls perform similarly to our Model S and X battery packs, the PowerWalls will probably be OK as long as you stay above 5-10% of charge and don't stay above 90-95% charge for extended periods.

The greatest risk to our PowerWalls could be the use of Storm Watch - when our PowerWalls are sitting at 100% charge for multiple days, ready to power the house for an extended outage if a hurricane disrupts power.

And, I'm assuming Tesla has included in the PowerWall some protection for the batteries when the pack is fully charged (it's possible Tesla has some cushion designed in so that 100% of charge is actually less than 100% of the battery capacity).

When designing our system, we assumed we would lose some capacity over a 10 year period, and after that, the PowerWalls may need to be replaced - or, more likely, by then there will be a "refresh" program to restore some capacity to old packs.

 

[jboy210]

Assuming PowerWalls perform similarly to our Model S and X battery packs, the PowerWalls will probably be OK as long as you stay above 5-10% of charge and don't stay above 90-95% charge for extended periods.

The greatest risk to our PowerWalls could be the use of Storm Watch - when our PowerWalls are sitting at 100% charge for multiple days, ready to power the house for an extended outage if a hurricane disrupts power.

And, I'm assuming Tesla has included in the PowerWall some protection for the batteries when the pack is fully charged (it's possible Tesla has some cushion designed in so that 100% of charge is actually less than 100% of the battery capacity).

When designing our system, we assumed we would lose some capacity over a 10 year period, and after that, the PowerWalls may need to be replaced - or, more likely, by then there will be a "refresh" program to restore some capacity to old packs.

The Powerwall comes with a guarantee of 70% retention of charge after 10 years with unlimited recharge cycles.

I set mine to drop down to 10-15% and charge to 100%. They are charged and discharged daily. If they can't meet the warranty conditions I will giveTesla a service call. My guess is the call will result in replacement by a new powerwall based on the current battery cell technology.

 

[AxlxA]

I'm using time based advanced setting. Is there a way to set charging max to 90%?

 

[acalbear]

I'm using time based advanced setting. Is there a way to set charging max to 90%?

Have the same question. I'd like the option of not having to fill PW to 100% when using time based settings.

 

[jjrandorin]

I'm using time based advanced setting. Is there a way to set charging max to 90%?

Have the same question. I'd like the option of not having to fill PW to 100% when using time based settings.

No