Phoenix Heat + Powerwalls = shortened Lifespan?

[teasla]

So it’s generally known that high temperatures can drastically reduce a rechargeable battery’s “max cycle” count.

With the recent heat wave and temps easily exceeding 110 F continuously for over three weeks (and more to come), is there any reason to be optimistic that the powerwalls installed in Phoenix are not going to die prematurely?

 

[aesculus]

Well good question and probably who knows? They have a liquid cooling system and fans, but mine when the temps exceed 100F often get to 38F+ for a period. I guess we will find out.

My average days over 100F is about 25 per year now and my PWs have not degraded even 1% after 3 years. They are on Time Based Control so they get cycled almost daily from 100% to 20-40%.

 

[jjrandorin]

So it’s generally known that high temperatures can drastically reduce a rechargeable battery’s “max cycle” count.

With the recent heat wave and temps easily exceeding 110 F continuously for over three weeks (and more to come), is there any reason to be optimistic that the powerwalls installed in Phoenix are not going to die prematurely?

They have a warranty that states they will retain at least 70% of their capacity the first 10 years they are installed, so if they reach that threshold, the warranty would apply (assuming by "die prematurely" you mean during the first 10 years, and more than 30% capacity lost).

 

[ucmndd]

Heat is the enemy of lithium batteries. So yes, expect them to degrade faster than those that aren’t being cooked.

That said, they have a warranty, so…

It was 106 here today. My un-insulated garage where the powerwalls are was every bit as hot. They run the fans at a pretty high speed when it’s that hot, but that’s all I notice.

 

[Matt-FL]

Mine are in my garage, it's been hot here to (Florida). My garage faces north, so I don't get a ton of heat transfer through the garage door, and I have a heat pump hot water heater that sucks hot air out of the garage and converts to hot water, expelling cold air. That keeps my garage in the high 80s on very hot days.

Powerwall Dashboard pulls PW temp data so you can track over time. Might be helpful to know just how hot they are getting during the day.

GitHub - jasonacox/Powerwall-Dashboard: Grafana Monitoring Dashboard for Tesla Solar and Powerwall Systems

Grafana Monitoring Dashboard for Tesla Solar and Powerwall Systems - jasonacox/Powerwall-Dashboard

github.com

 

[bwb1]

I live in Rancho Mirage, CA and have temps similar to AZ. I have a mini-split unit for the garage that keeps my two Powerwalls and two Tesla vehicles at about 82 degrees all summer.

 

[Matt-FL]

I do have a 2 ton mini-split in my garage, however it is only used when I am in there woodworking or fabricating. My garage has an insulated garage door, and the wall that is attached to the house. The rest is not. It would run constantly, and we use enough electricity as it is. Here in the summer, my 4 powerwalls drain from 100% to 35% each night. With that running, I'd be in the teens at best.

 

[CrazyRabbit]

I’m in Fort Worth, the compressor shuts off around 2 am and starts up around 10 am. Most of the time it is only pulling .5kw per hour. Temp is set at 82F. Now I can leave my other batteries in the garage, like for the Z6…

 

[ArizonaJon]

Mine are in my garage, it's been hot here to (Florida). My garage faces north, so I don't get a ton of heat transfer through the garage door, and I have a heat pump hot water heater that sucks hot air out of the garage and converts to hot water, expelling cold air. That keeps my garage in the high 80s on very hot days.

Powerwall Dashboard pulls PW temp data so you can track over time. Might be helpful to know just how hot they are getting during the day.

View attachment 959155

GitHub - jasonacox/Powerwall-Dashboard: Grafana Monitoring Dashboard for Tesla Solar and Powerwall Systems

Grafana Monitoring Dashboard for Tesla Solar and Powerwall Systems - jasonacox/Powerwall-Dashboard

github.com

Very interesting. Please share your ideas on why PW 1 & 3 run about 3 degrees hotter. Are they in a 2 x 2 stack?

 

[Matt-FL]

Great question! I posted on this very topic a few weeks ago. They are stacked.

Temperature Impacts of Stacked Powerwalls

The other day I installed and setup Powerwall-Monitor, which is an amazing tool if you haven't use it. One thing that stuck out to me was the impact of stacking and temperature. The temperatures are slightly higher for the inside powerwalls, but obviously well within limits. Just thought I'd...

teslamotorsclub.com

 

[3rror]

I have also recently considered Powerwall and I am in AZ. My garage during this heatwave has been about 106 degrees during the daytime and usually sits in the evenings at around 101 degrees until around 10:30 in the evening. The last couple nights have been up to 100 degrees even up until about midnight. I don't know how well this works with or degrades Powerwall? I already have Tesla Solar and I'm on my 3rd inverter since having it installed in October 2019. The PW will cost me around $16K up front here, so I'm not sure if I should make that purchase or not? I know during our winters I usually get an electric bill credit, but I have a feeling that I actually use a lot of my Solar production during the miserable hot months here, so I'm not sure how much the PW can actually fill up while my AC is running for the greater portion of the day?

 

[Matt-FL]

The units have fans in them, so I imagine they are no different than what an EV sitting in your driveway would experience, maybe less if in your garage. Couple that with the 70% capacity at 10 year warranty, that puts a lot of the weight on Tesla that the unit will run in those temperatures based on their own rating.

As far as how it might help in your situation, I suppose you'll need to see how many days in the summer you are able to push back kWh back to your utility (that would then in turn go to a powerwall). If you are consistently pushing 13kwH most days, then you won't have any trouble charging it on a daily basis.

As others have stated, PWs make financial sense if you have high TOD usage rates or opportunities to be a powerplant.

Personally, I didn't see a decent ROI for powerwalls, however I got them for peace of mind. They are my 10+ year generators that need zero maintenance.

HTH

 

[ArizonaJon]

For AZ there is not any real ROI for PWs. The peak to non-peak rates are to close. Not like parts of CA where the differ by up to 30 cents per kWh. In Tucson, the delta is only about 3 cents per kWh.
The ROI I get is not having AC shut off, clocks to reset, etc. during a power failure. We had a real bad storm last night and the power went off twice for about 1 and 3 minutes respectively (prior outage was 3 hours), but I didn't even see a blip on the evening news that I was watching.

 

[ptdusn]

As @ArizonaJon says the major benefit of PWs is not losing A/C in the summer. Right now, we are running the house off the PVs in the day and our PWs last just long enough, before hitting the reserve I have set, to get up past the Peak period at 8:00pm. Wintertime is when we are feeding a bunch back to the grid and knocking the $32 service fee down to almost zero. Two times in March, a week apart, our neighborhood lost power for an hour each time. We didn't due to the PWs, which in my opinion made them pay for themselves.

 

[Matt-FL]

For AZ there is not any real ROI for PWs. The peak to non-peak rates are to close. Not like parts of CA where the differ by up to 30 cents per kWh. In Tucson, the delta is only about 3 cents per kWh.
The ROI I get is not having AC shut off, clocks to reset, etc. during a power failure. We had a real bad storm last night and the power went off twice for about 1 and 3 minutes respectively (prior outage was 3 hours), but I didn't even see a blip on the evening news that I was watching.

Similar situation here, very little ROI in Florida for PWs (sell rate = 1/3 of buy rate). For me, it was for peace of mind and, albeit an expensive generator, having zero maintenance and not having to bury propane tanks (no natural gas here) is a huge plus. I have found that the PWs do add benefit, similar to @ptdusn, in my case having enough reserve to run my house during the night before recharging the next day which has greatly accelerated my solar ROI. My original predictions/calculations were about 8 years for just solar, 11.5 years for solar + PWs. My actual calculations (if they continue as they have for this year) are 5.6 years solar and 9.8 years for solar + PW, just in time for warranty expiration. I expect to get at least another 5 years post warranty out of the PWs, and lots more years from the Tesla 400w panels.

In 11 months, I've imported 1,200kWhs, and exported 4600kWhs. I'd say a good third of the imported kWhs were in the first month where 'charge from grid' was locked turned on, along with 'stormwatch' until I could get Tesla support to unlock the settings. In any case, 1,200kWh is less than half of what I used to import in a single month prior to PV. A major reason for that low number is the PWs.

Of course, If I didn't have PWs, I would have exported an additional 10,800kWh. When added up would be about $972 in credits. I would also (have to guess here) imported about half of that to cover the house on less productive days and nights, which would have cost about $1,080.

I know I had a point when I started this response, but it has since left my brain. I guess you can call this a general rambling about PW ROI.

 

[CrazyRabbit]

I wish tesla would have designed powerwall with the ability to add a optional cooling/heating heat pump to the cooling loop.

 

[Don_Singer]

I live in Phoenix and have SRP so the buy/sell difference on-peak to 3X, 8 cents off-peak, 28 cents on-peak up until 8pm so the PV is not generating much if any energy and the system should use PW.

My issue is that when it is hot, like in the summer, the PW throttles its output to 1.0kw, both my HVACs pull 6+kw so my Tesla system primarily relies on the grid during on-peak times, so there really isn't any savings. Tesla says this is normal.

Not really capacity longevity in hot climates but severely limited performance.

 

[Matt-FL]

My issue is that when it is hot, like in the summer, the PW throttles its output to 1.0kw, both my HVACs pull 6+kw so my Tesla system primarily relies on the grid during on-peak times, so there really isn't any savings. Tesla says this is normal.

That is great information, I wasn't aware of this limitation. I'm curious what the Powerwall temp cutoff is for the throttling to kick in...

 

[cali8484]

Not really capacity longevity in hot climates but severely limited performance.

Technically true but still related as it's a heat issue. If the PW didn't throttle output then it could cause longevity issues. It appears Tesla has prioritized longevity over performance.

 

[ptdusn]

I live in Phoenix and have SRP so the buy/sell difference on-peak to 3X, 8 cents off-peak, 28 cents on-peak up until 8pm so the PV is not generating much if any energy and the system should use PW.

My issue is that when it is hot, like in the summer, the PW throttles its output to 1.0kw, both my HVACs pull 6+kw so my Tesla system primarily relies on the grid during on-peak times, so there really isn't any savings. Tesla says this is normal.

Not really capacity longevity in hot climates but severely limited performance.

I live in Gilbert in the East Valley and my PWs DON'T throttle output due to the heat?