PowerWall and "The Missing Piece..." Event

[EldestOyster]

I had decided to withhold my snarky remarks about the gas tax allegedly going to fix the roads. But, yeah, that :smile:

 

[Owner]

I agree. Particularly for those of us who have known and met other CEOs personally....one of which was VERY well known and the encounter was not pleasant.

In my opinion, Elon is the most likable and identifiable billionaire CEO, visionary maybe ever. If you didn't know it, you would think you're listening to your nerdy buddy in algebra class, or your quirky college roommate late at night cramming for finals hyped up on red bull fumes. He expresses his fears, foibles, but never gives up on reaching higher for all his friends and family(and the rest of us too). Elon is using his mind to have the courage to follow his heart and that's something we wish to do in our own lives. His palpable fear of public speaking just makes him more endearing and real and that's something rare in this world of polished, calculating, and distant, and scripted CEOs looking no further then their golden parachute. Elon is the business Titan of our times and needs to be emulated for generations to come.

 

[ReversePolarity]

I do get the impression that plugging them into an existing solar string inverter is the current use case as it stands. I still don't see the financial benefit to doing so, however. See my analysis of such things in my other thread.




Grid arbitrage is not going to work out well with this without solar. See my other thread.

Wk057, I do agree, there is some unknowns with the loss associates with whole "Roundtrip" issue ie pushing off-peak power onto the battery to use. Based on your extensive experience in this field I think you're definitely onto something in not embracing the practical usage... I'm just going by the numbers, and the ROI seems to depend heavily on tax benefits... After all a profitable business taking a tax deduction is similar to getting a 40% discount on the power storage. But who knows, just need to wait for some of the early adopters to report some real world numbers.

 

[Papafox]

If the 10kwh pack is not meant for daily cycling, then it could possibly be defended for tax purposes for use primarily as a standby battery. Although I toyed with the power shifting idea, my real reason for getting one of these is to enable my house to continue operating from PV panels after the grid goes down. Thoughts?

 

[TheTalkingMule]

Does this product open the option for an RV type vehicle power system paired with solar? Certainly seems small enough to fit in a generator sized compartment and could be paired with something like roll out solar awnings, no?

 

[austinEV]

Sorry if it has been discussed, but do you think the scale on his carbon chart was intentional or a mistake? Some people on Reddit are pointing out that the scale goes linearly in 100 year increments but the next increment after 2000 is 3000, not 2100. During the presentation I figured it just meant that meant he was being LESS alarmist suggesting that it would take hundreds of years to get really bad. But I think that exponential rise is usually shown to happen by 2100.

 

[brucet999]

this would not let one go off grid unless you live near the equator, or have a huge number of solar panels.

+1

Ours is a modest house in SoCal near the beach, so no need for heavy power loads like air conditioning. We have a gas dryer, water heater, furnace and stove, one small EnergyStar freezer, and a fridge, just wife and me so not a lot of laundry. Even so, we averaged 11.73 kWh per day over the past 12 months. If we went off grid, the 10kWh Powerwall would not carry us through one sunless day.

For those with time-of-day metering, it might be enough to load-shift from peak rates to off-peak rates I suppose.

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I think you're severely underestimating the solar power generation during non-summer months. Nonetheless, it's impossible for anyone to tell you if the Powerwall makes financial sense without knowing your monthly energy consumption, your exact variable rates, and your monthly solar power generation. Without those details, it's just a guessing game that doesn't serve any real purpose.

It appears to me that "Owner" gave us all the info necessary. He is on net metering, generating about the same amount of power annually as he uses, and his monthly connection charge is small enough not to make much difference. The only benefit he would likely get would be ability to get through Grid power outages without going dark.

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People here have commented on why they won't buy this product. Here are my thoughts as to why I am going to line up (all alone) outside Tesla here and buy the very first unit I can get my hands on.

First power here is expensive (with a capital E).

- Grid power costs $0,33 pr kWh (all prices in $US) and 80% of that is tax.
- Solarpower shipped to the grid can be used inside of an hour with no penalty. Hence the grid is a 1-hour battery.
- Solarpower sold back to the grid gives me $0,195 pr kWh.

Since we are not home at noon and can't use our solarpower this means that we effectively become an underpaid generator for the grid. The Powerwall would allow us to run without the grid for approx. 150-250 days pr year. It really makes solarpanels a much better deal than before and as an added bonus the tax-man never sees a dime.

Our daily usage is between 8-14 kWh's and with just a little work we could probably get below 8 kWh all the time.

So to sum it up: I want this powerwall and I wanted it yesteryear.

You are, indeed, the ideal candidate for Powerwall. In most US locations, solar panels are connected under net-metering rates, so power from the Grid and power sent to the Grid are tracked and at year's end the difference is either charged to the user or credited. Home owners may elect to sell any credits to the PoCo at a lower than retail rate. This reduces the utility of Powerwall to backup power in case the Grid is down (our solar inverters will not work unless they "see" Grid power to sync with) or for non-solar panel consumers with time-of-day rates, to shift power use from peak hours of higher rates to off-peak hours with lower rates.

 

[InTheShadows]

If the 10kwh pack is not meant for daily cycling, then it could possibly be defended for tax purposes for use primarily as a standby battery. Although I toyed with the power shifting idea, my real reason for getting one of these is to enable my house to continue operating from PV panels after the grid goes down. Thoughts?

From the specs, my very strong suspicion is that the 7kw will easily be defended for the tax credits.

The output looks to me like it will go between solar panels and a new or existing solar inverter. No possible way to charge it from the grid to load shift. It will get all of its energy from the sun, and take the early morning energy, store it and dump it from 6-9pm, this shaving off the peak that occurs when the sun is setting.

In this scenerio, there is no question wether it would qualify for the ITC.

 

[Papafox]

From the specs, my very strong suspicion is that the 7kw will easily be defended for the tax credits.

The output looks to me like it will go between solar panels and a new or existing solar inverter. No possible way to charge it from the grid to load shift. It will get all of its energy from the sun, and take the early morning energy, store it and dump it from 6-9pm, this shaving off the peak that occurs when the sun is setting.

In this scenerio, there is no question wether it would qualify for the ITC.

Thanks for this interpretation, Theshadows. Although I currently have microinverters on all my 54 PV panels, the microinverters are failing at a pretty good clip right now (about 10% in the past year). I may choose to have microinverters removed from some of the PVs (if that is possible), hold onto the good microinverters as spares, are then take the DC current from the modified PV panels, run it through the Powerwall batteries, then use a traditional inverter to connect with my system. The whole idea is to enhance the reliability of my electric power at the house and provide backup power for times when the grid is down. If I get tax breaks, I'd probably go for two 7kwh powerwalls. I'm hoping if my panels are producing 30kwh or more in a day that I could pass some of that current through the powerwall (or bypass) and use more than 14kwh of PV power that day when the grid is down.

 

[InTheShadows]

Thanks for this interpretation, Theshadows. Although I currently have microinverters on all my 54 PV panels, the microinverters are failing at a pretty good clip right now (about 10% in the past year). I may choose to have microinverters removed from some of the PVs (if that is possible), hold onto the good microinverters as spares, are then take the DC current from the modified PV panels, run it through the Powerwall batteries, then use a traditional inverter to connect with my system. The whole idea is to enhance the reliability of my electric power at the house and provide backup power for times when the grid is down. If I get tax breaks, I'd probably go for two 7kwh powerwalls. I'm hoping if my panels are producing 30kwh or more in a day that I could pass some of that current through the powerwall (or bypass) and use more than 14kwh of PV power that day when the grid is down.

Let me guess, Enphase.

They are the next Tesla battery killer didn't you know?

http://enphase.com/wp-uploads/enphase.com/2014/10/Enphase-AC-Battery-Brochure-1.pdf

I think this product will the the one that ends them for good.

They want to put small packs of lifepo4 batteries on people's roofs. Where it easily hits 180 deg F.

We send guys out every week to do warranty work on Enphase systems.

 

[beeeerock]

Let me guess, Enphase.

They are the next Tesla battery killer didn't you know?

Just tried to PM you on micro-inverters in general... message bounce, said your inbox quota has been reached...!

 

[dhanson865]

Let me guess, Enphase.

They are the next Tesla battery killer didn't you know?

http://enphase.com/wp-uploads/enphase.com/2014/10/Enphase-AC-Battery-Brochure-1.pdf

I think this product will the the one that ends them for good.

They want to put small packs of lifepo4 batteries on people's roofs. Where it easily hits 180 deg F.

We send guys out every week to do warranty work on Enphase systems.

Have you seen this thread?

My Nissan Leaf Forum View topic - Enphase field MTBF: M190: ~50 Years M215: ~925 Years and the spreadsheet at Enphase Microinverter and Envoy Field MTBF Estimate - Google Sheets

Reg is serious about tracking failures on M190 (Also includes M380 models) and M215.

I'm in TN and still haven't decided on the micro vs string inverter but I'm leaning towards Enphase for functionality/reporting and either way when it comes to price/reliability (as in I'm open to actual data and will let that sway my decision).

oh, and no I don't want batteries on my roof, I'd rather have them in my garage where the AC spillage from my living space and the heat pump water heater keep the garage no warmer than 80F at the worst.

 

[Phil Seastrand]

As another data point: We've had solar with Enphase (44 panels) for 5 years and I had one inverter die within the first 6 months, then no failures since (knock on wood). I have intermittent shading problems and would have lost significant generation if I went with the traditional monolithic inverter. YMMV.

 

[InTheShadows]

We installed 1209 Enphase micro inverters before we realized there were reliability issues. I asked our PM to run a report for me tomorrow to see exactly how many inverters we have replaced.

Tesla Motors chose SolarEdge string inverters that have a panel level optimization system. They handle shade down to the panel level and they are also much safer to work on.

SolarEdge: maximum PV energy at a lower cost - Part 1/3 - YouTube

In my experience with solar inverters there is no doubt in my mind that Tesla chose the right partner.

We only install SMA and SolarEdge inverters and there is a reason for that.

 

[Foghat]

We installed 1209 Enphase micro inverters before we realized there were reliability issues. I asked our PM to run a report for me tomorrow to see exactly how many inverters we have replaced.

Tesla Motors chose SolarEdge string inverters that have a panel level optimization system. They handle shade down to the panel level and they are also much safer to work on.

SolarEdge: maximum PV energy at a lower cost - Part 1/3 - YouTube

In my experience with solar inverters there is no doubt in my mind that Tesla chose the right partner.

We only install SMA and SolarEdge inverters and there is a reason for that.

To add, I've also heard Solarcity is solarEdge's largest customer, so they also may be collaborating on a total pv+powerwall package currently as well.

 

[Papafox]

Let me guess, Enphase.

Guilty as charged ; ) Sounds like I have all the more reason to dump the Enphase microinverters and go with a string inverter for a bunch of the panels. Now, if I can just find out if that's possible. I understand the issues of shade and orientation when changing from microinverters to a string inverter.

 

[InTheShadows]

Guilty as charged ; ) Sounds like I have all the more reason to dump the Enphase microinverters and go with a string inverter for a bunch of the panels. Now, if I can just find out if that's possible. I understand the issues of shade and orientation when changing from microinverters to a string inverter.

0 issues if you go with Solar Edge.

If your shading isn't too bad, the new SMA -22 series are really good too. Not as good as Solar Edge though.

 

[Papafox]

0 issues if you go with Solar Edge.

If your shading isn't too bad, the new SMA -22 series are really good too. Not as good as Solar Edge though.

Many thanks!

 

[tga]

Let me guess, Enphase.

They are the next Tesla battery killer didn't you know?

http://enphase.com/wp-uploads/enphase.com/2014/10/Enphase-AC-Battery-Brochure-1.pdf

I think this product will the the one that ends them for good.

They want to put small packs of lifepo4 batteries on people's roofs. Where it easily hits 180 deg F.

We send guys out every week to do warranty work on Enphase systems.

Agreed, putting batteries on the roof is stupid, but the "AC Battery" brochure says nothing about roof mounting. "Install mounting bracket on studs", "Flexible configurations for any garage" says to me they clearly intend them to be mounted inside the house.

FWIW, it's only one data point, but I have 36 M215's that are a little over 1 year old with no issues.

Tesla Motors chose SolarEdge string inverters that have a panel level optimization system. They handle shade down to the panel level and they are also much safer to work on.

So are you saying that the optimizers can handle complete shading of a panel? Is there a limit to the number that can be shaded (absolute #, or % of string)? I couldn't find that clearly stated in the brochures I looked at.

Why are the safer to work on? Are you comparing low voltage DC at the panel to 240VAC coming out of the micro inverter?

 

[InTheShadows]

Here's the stats from our Enphase failure rate.

Installed Units,Failed,ratio
1231,106,11.61

It's likely worse than that because some of the monitoring units have failed and customers don't want to plunk down 350 to replace them. Also Enphase will not replace inverters that are not hooked up to their monitoring system.

Edit: fixed typos.