Elon, I love you... but the PowerWall isn't that great...... yet.

[Evbwcaer]

The difference is my electricity cost for the a ToU customer, over 10 years at 1000kwh/month @ 2 cents KwH, is .02*1000*12*10= $2,400.

Why do you have $10,800?

 

[wk057]

It's not just the inverter. If the PowerWall battery needs to be heated before you can draw full power out of it (ala Model S), there is nothing that the inverter can do by itself to overcome that.

True, however I would think this is factored into the 2kW continuous draw rating, which is only 1/5C. The Model S pack can draw that from the pack when its very cold without issue while using some power to heat the pack.

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The difference is my electricity cost for the a ToU customer, over 10 years at 1000kwh/month @ 2 cents KwH, is .02*1000*12*10= $2,400.

Why do you have $10,800?

Your ToU example was 9A-9P on peak and 9P-9A off-peak. A 1000kWh/mo customer without a PowerWall at a constant load would have 500kWh on peak and 500kWh off-peak. (500*$0.02) + (500*$0.16) = $90/mo = $1,080/yr = $10,800 over 10 years.

As I pointed out, even with the PowerWalls you can not shift 100% of usage over to off-peak, and certainly not without them. You can only shift 14kWh worth (max at 100% efficiency, more like 13kWh in reality), which is less than expected on-peak usage per day (~17kWh on the constant load scenario). See the spreadsheet for an hour by hour breakdown.

Edit: You really don't even need the breakdown to do the math. We can just take the $90/mo number and assume that the output from the PowerWalls can move 14kWh worth of on peak time to off peak time, a difference of $0.14/kWh, or $1.96/day in savings at 100% efficiency. No need to get too complicated.

 

[GSP]

Assume it was a $$$ tie, are there meaningful environmental gains to be had?

For an off-grid system: no noisy and smelling generator, no carting fuel to it, and no generator maintence. Just a solid-state PV-battery system that just works for ten years or longer, with no maintence.

Very attractive for remote locations and island residents with costly petroleum produced electricity.

GSP

 

[CalDreamin]

I took a stab at estimating the value of integrating a Powerwall into a solar PV system, using PG&E's EV rate plan. I premised that the Powerwall would be installed between solar PV panels and an existing inverter, and assumed this is a simple, relatively low cost ($500) installation. I assumed 7 kWh of PV solar would be moved every day, shifting partial-peak energy to peak energy on weekdays, and off-peak energy to peak energy on weekends and holidays. Taking into account 92% efficiency, the payback looks to be about 8.4 years. This system doesn't provide battery backup or allow grid arbitrage; need some additional hardware for those capabilities.

Over the next several years a lot more solar will be installed in California. When that happens, I expect that most solar PV energy will become off peak, while peak rates will be something like 5 pm to 10 pm. Payback improves to about 5.9 years in that scenario. In addition to that, if the Gigafactory decreases the Powerwall cost by 30% over the next several years, payback improves to about 4.4 years.

Edit: Battery storage added to a solar PV system is reportedly eligible for the 30% federal tax credit. If that is the case, the estimated payback decreases from 8.4 years to 5.9 years. In the future case where I premise PG&E's off-peak rate for all solar PV time shifted to peak, the payback improves to 4.2 years, and further improves to 3.1 years if the Gigafactory decreases Powerwall cost by 30%.

 

[callmesam]

I took a stab at estimating the value of integrating a Powerwall into a solar PV system, using PG&E's EV rate plan. I premised that the Powerwall would be installed between solar PV panels and an existing inverter, and assumed this is a simple, relatively low cost ($500) installation. I assumed 7 kWh of PV solar would be moved every day, shifting partial-peak energy to peak energy on weekdays, and off-peak energy to peak energy on weekends and holidays. Taking into account 92% efficiency, the payback looks to be about 8.4 years. This system doesn't provide battery backup or allow grid arbitrage; need some additional hardware for those capabilities.

Over the next several years a lot more solar will be installed in California. When that happens, I expect that most solar PV energy will become off peak, while peak rates will be something like 5 pm to 10 pm. Payback improves to about 5.9 years in that scenario. In addition to that, if the Gigafactory decreases the Powerwall cost by 30% over the next several years, payback improves to about 4.4 years.

Edit: Battery storage added to a solar PV system is reportedly eligible for the 30% federal tax credit. If that is the case, the estimated payback decreases from 8.4 years to 5.9 years. In the future case where I premise PG&E's off-peak rate for all solar PV time shifted to peak, the payback improves to 4.2 years, and further improves to 3.1 years if the Gigafactory decreases Powerwall cost by 30%.

@CalDreamin,

At the Tesla Energy press conference, Elon singled out Germany, Hawaii and California as good candidates initially.

CA has rebates on batteries at 1.46 $/W

About the SGIP


What does Germany have in terms of feed-in value?

Will they get paid for arbitrage in a system designed to shift pay producers directly?

Will the car's battery become a mobile asset, PAID to charge at various parking facilities so that property owners can integrate the cars into a new energy "system" and prevent power spikes and TOU charges.

@OP,

Agree that the use case for a single pack is marginal without solar. And scaling doesn't begin to work until you get to the module level.

When the cost of the 100kWh is $25,000, I start to think that this is the path forward since it includes so much more.

(If anyone can help with pics . . .)

Interesting to note that there are 14 modules x 7kWh likely means that these are the more advanced battery cell composition and NOT the "stock" Panasonic that may be in the 10kWh PowerWall modules.

 

[Johan]

Interesting to note that there are 14 modules x 7kWh likely means that these are the more advanced battery cell composition and NOT the "stock" Panasonic that may be in the 10kWh PowerWall modules.

Very good observation. It suggests that the "large scale units" have the "daily cycler grade" cells rather than the "weekly cycler grade" ones (whatever this means in reality). I would expect nothing less since of course a large customer like a utility, a factory or a data center would want to cycle their storage aggressively to maximize their ROI.

 

[lolachampcar]

I keep reading all the posts referring to, and using for calculations, the PowerWall as a 7 KW-Hr device. Even if the PW is charged directly from PV DC, you still have DC to AC inverter losses meaning the daily cycle PW is really only good for about 80% of the rated 7 KW-Hr battery capacity or 5.6 KW-Hr of usable AC. Its like my 10 KW PV array that, at most, provides 8 KW of usable AC to my house. The inverters are hungry.

 

[liuping]

@CalDreamin,

At the Tesla Energy press conference, Elon singled out Germany, Hawaii and California as good candidates initially.

CA has rebates on batteries at 1.46 $/W

About the SGIP

I was wondering about SGIP in California. Is that program still running and does it have any funds left?

At $1.46 per watt, the SGIP rebate would be $10,220 for a 7kWh system. That does not seem right as that would make the cost less than $0 for CA residents.

 

[callmesam]

Very good observation. It suggests that the "large scale units" have the "daily cycler grade" cells rather than the "weekly cycler grade" ones (whatever this means in reality). I would expect nothing less since of course a large customer like a utility, a factory or a data center would want to cycle their storage aggressively to maximize their ROI.

During the Q&A before the event at 8pm, Elon was asked if the Powerwall had the same chemistry as the car and he said no. "Some" of the packs had different chemistries. I've made some assumptions with less than great data.

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I was wondering about SGIP in California. Is that program still running and does it have any funds left?

At $1.46 per watt, the SGIP rebate would be $10,220 for a 7kWh system. That does not seem right as that would make the cost less than $0 for CA residents.

Seems right by calculation, but isn't the system output 2kW?

Powerwall specs:

• Mounting: Wall Mounted Indoor/Outdoor
• Inverter: Pairs with growing list of inverters
• Energy: 7 kWh or 10 kWh
• Continuous Power: 2 kW
• Peak Power: 3.3 kW
• Round Trip Efficiency: >92%
• Operating Temperature Range: -20C (-4F) to 43C (110F)
• Warranty: 10 years
• Dimensions: H: 1300mm W: 860mm D:180mm

Press Kit | Tesla Motors

Then the SGIP rebate would be $1,022 which seems more reasonable.

 

[Foghat]

One major reason Powerwall will be extremely popular: agregated DG... Virtual power plant. Customers will opt into the virtual power plant plan through Solarcity with the local utilties and receive price per kWh credit. Since Solarcity will have control of over 2GWs of capacity or approximately 2.8-3TWhs/yr by YE2015 alone, they could really offer the utilties a tremendously valuable asset very fast as they approach projected 9-10thws/year within the next three years. By this model, those customers with pv+solar will see much higher savings on their electricity bill compared to pv only or regular grid utility customers. Solarcity has guided for 1mln customers by 2018, so I see a lot of powerwalls being sold in short order, making powerwall pure genius and on he money in my book for this reason alone.

 

[jerry33]

Edit: In reality this entire hypothetical is contrived in favor of the PowerWall, and it still fails. In reality your loads will exceed 14kWh during peak times, and be lower during off-peak (hence the terms) which would make the advantage of the whole thing cancel out entirely for the ToU savings, and make the PowerWall even more expensive in the long haul.

Well, if you add the cost of a UPS (I have a 6 KVA one which cost more than a couple of Powerwalls ten years ago--and the six battery packs have had to be replaced occasionally) it wouldn't fail. Of course, I don't have solar or TOU, and my cost of electricity from renewable sources is less than $0.10, so the calculation won't work for me either, but should I have to replace the current UPS, it would be with a Powerwall. (I have to redo the wall int he bedroom anyway

 

[nwdiver]

So... is the total battery voltage 350/400 or is that the DC voltage it can accept from an array; How does it work off-grid? AC-coupled? They did a piss poor job explaining how it works...

Saying it works 'seamlessly' with Solaredge and Fronius inverters doesn't help... those inverter cannot work off-grid....

 

[woof]

So, what in your opinion needs to change to make it great? Price, power output, kWh? You had the "...yet" part in the title but I don't see the solution here (perhaps I missed that).

 

[Skotty]

To add another opinion -- I think suggesting it's not a product worth buying due to it's cost effectiveness is kind of silly in the USA. The grid is quite stable here, power rarely ever goes out, and when it does, it's usually only for a few hours. No one here needs a stand by generator. People don't buy stand by generators or the little portable gas generators because they are needed. It's a luxury purchase. The same is true for the Powerwall. It doesn't need to pay for itself. It just needs to be competitive with other generators. Price/performance-wise, I think the Powerwall is a little pricey, but it's one HUGE advantage, in my humble opinion, that makes it worth it is that it is quiet. Gas powered generators, stand by and stand alone, are both really frickin loud. That alone is worth a ton of money to me.

 

[mitch672]

There is another use case never mentioned. I have a house in a condo community (they are seperate houses that fall under a HOA). We cannot modify or add anything to the exterior of the building.. This means no solar panels on the roof, or any kind of backup generator outside of the house (even though every house has natural gas). With the powerwall, I can install a whole house UPS, if I wanted.. There is plenty of space on the interior garage wall. Also hoping that after the residents take over the HOA (currently the builder runs it), we can try and push to allow for Solar arrays on the roofs, everyone is aware of the high electric rates after this winter, and might not oppose solar for the houses that have the correct southern exposure for it.

 

[Tedkidd]

Great post, particularly this:

To ROI in 7 years (a reasonable long term investment, beyond this it's best to invest elsewhere usually) the unit would have to save about $1.18/day @ $3000. This isn't counting installation and other equipment needed. At a daily cycle, 7kWh per day, those kWh would each need to save at least $0.168 after efficiency losses.

I see powerwall solving duckneck. Ultimately we'll probably be able to set our buy and sell rates.

I imagine a day when you do this with your car also. Most people seem to rarely need all their capacity - I don't with 18 kwh... So leaving say, 2/3 of your 85 pack available for peak flattening at whatever price you deem or the market pays (sometimes North of $2 a kWh?). And this provides significant societal benefit as building new peaker plants and substations can be avoided.

 

[MattMDK]

SolarCity only installing PowerWall for NEW customers

I've had a solar system from SolarCity for three years. I was surprised to hear from my rep that they will only be installing the PowerWall for NEW customers. I would be considered a new customer if I added additional panels to my system. They are selling the 10kw PowerWall for $5000 installed. I told him I was surprised that a loyal customer and Tesla owner was being told that new customers took precedence. He said new customers currently can get the PowerWall in Sept/Oct. He did not have a date for existing customers, but didn't expect it to be this year. He also said even if I ordered it directly from Tesla, SolarCity is the only one authorized to install and integrate with their solar system. Disappointing. Has anyone else heard this yet?

 

[TheTalkingMule]

There is another use case never mentioned. I have a house in a condo community (they are seperate houses that fall under a HOA). We cannot modify or add anything to the exterior of the building.. This means no solar panels on the roof, or any kind of backup generator outside of the house (even though every house has natural gas). With the powerwall, I can install a whole house UPS, if I wanted.. There is plenty of space on the interior garage wall. Also hoping that after the residents take over the HOA (currently the builder runs it), we can try and push to allow for Solar arrays on the roofs, everyone is aware of the high electric rates after this winter, and might not oppose solar for the houses that have the correct southern exposure for it.

And there are TONS of these 55+ communities where solar will eventually become acceptable, but exterior generators will not. My parents had a nat gas generator installed in New Jersey 2 years ago out of medical need and were required to go in front of the HOA board a bunch of times to get approval, but there are plenty of places that will not bend.

Considering the $14k cost of their generator, I'm sure they'd just go with 3 of the new Tesla backups in concert with solar if they had to do it again and be much happier. There's definitely plenty of demand for this product and then once it's twice as good for half the cost it'll be universal.

For now, people who have solar and live anywhere near trees and thunderstorms could use this system for the summertime when they lose power for a couple days at a time a few times a summer plus once or twice in the winter. So long as your grid tied solar can charge this thing during an outage.

 

[scaesare]

They are selling the 10kw PowerWall for $5000 installed.

So, given that you already have solar, I assume that did not include an inverter in the price?

 

[DFibRL8R]

For now, people who have solar and live anywhere near trees and thunderstorms could use this system for the summertime when they lose power for a couple days at a time a few times a summer plus once or twice in the winter. So long as your grid tied solar can charge this thing during an outage.

For this use (emergency/rare use for a grid outage of a few hours or longer), I would like to see Tesla allow an owner to tap into the massive (compared to PowerWall) amount of energy in a Model S battery. I can understand why they would not want the wear and tear on the Model S battery for daily use with the grid/time of use but I would rather not purchase more lithium ion batteries from Tesla or a stand alone ICE generator for this purpose. Even better, I can drive my battery to a friend's home to charge and come back with a full battery if needed in a more prolonged outage situation.