Tesla Powerwall $350 / kwh Retail

[Hillhater]

I hope those figures are comparing apples to apples, because that $250 /kWhr figure is pure cell cost, not installed cost.
The 7 kWhr home PowerWall module has been quoted as costing $7+ k installed with necessary ancillaries !
That's over $1000 per kWhr

SolarCity is only offering the bigger Powerwall to customers buying new rooftop solar systems. Customers can prepay $5,000, everything included, to add a nine-year battery lease to their system or buy the Tesla battery outright outright for $7,140. .

Obviously the commercial/ industrial systems won't have that pricing, but it won't just be cell cost either !

 

[Hillhater]

Can someone explain the intended function of the 7 kWhr PowerWall.
I get the 10kWhr unit as an emergency backup for power outages, and fully understand the logic of the large 250kWhr ++ modules for distribution utilities to cover power peaks and outages,.....
....but these 7 kWhr domestic " daily cycle" units do not add up ?
They only have a 2 kW continuous output rating, so would not support a cooking or heating appliance, would hardly boil a water kettle infact, let alone cover the "peak" demand periods , which by definition have high power draws.
A single unit would be unrealistic for a Solar system storage for night time cover...(many multiples would be needed).. And then the costs become impractical ( even tesla have said as much !)
At best, I can see they might carry a fridge/freezer and a few lights overnight for a off grid solar installation.
.....So , have I misunderstood their intended function ?....if so what should it be ?

 

[speedmd]

It would work for us. We run light stuff only and cook with gas or wood during the winter. Easily run our efficient frig, lighting and central heat burner /pumps.

 

[quamau]

Same here (Italy).

AFAIK, the 7kWh model is meant to maximize the percentage of solar energy that you use locally, and to avoid putting most of it back to the grid. There are many financial models for solar panels at work, and I guess some are (and will be) such that self-consumption becomes the most convenient option.

So the 2kW of power is just meant to cover most of the standard consumption, as any peak will be covered by the grid, which is already there (peaks are free, in a sense).

Here in Italy most houses get 3kW max power from the grid, hence 2kW would cover most of the use cases. I see a tendency to decrease max power, and the move of reducing max power of vacuum cleaners is a smart one that goes into that direction. Power can be traded with efficiency! Plus, the vacuum robots which are growing fast use very little power (1-2 tenths of W) when charging. The incandescent bulbs are out of market since a few years, same for halogen in the very near future, and this is another step towards abating max power requirements.

 

[spinningmagnets]

Can someone explain the intended function of the 7 kWhr PowerWall

Federal tax credits similar to the German model. Every time a new coal-fired electric generating plant is proposed in the US (we are the Saudi Arabia of coal, a thousand years worth is under our feet), the public votes it down (thats a separate issue).

If we can't build more coal burning electric plants, how can we power all those air-conditioners during the summer peak demand hours? Its called "time shifting", when the power walls charge up at night (when the coal plants are running at an idle speed), and then put electric back into the grid during 11AM-5PM peak heat hours.

Thats the first customer model, the second is "local net-metering" where houses that agree to have solar-PV panels mounted on their roof will get a price break on the install and monthly electrical use. houses with the solar panels and Tesla walls will feed the local grid during peak demand.

Existing coal will feed the Tesla walls at night, and the sun will feed the Tesla walls as soon as the sun comes up. People who don't participate will have their electric rates go up, people who join will feel slightly less financial pain.

The Gigafactory will have no problem finding a use for cylindrical 20700 cell that it makes for the next five years. Whe Tesla finishes endurance testing of their version of solid-state batteries, the power walls will still continue to use the 20700 cell, and the cars/motorcycles/ebikes will transition to using SSBs due to the smaller size per kWh. The Gigafactory(ies) can transition to making SSBs as the demand for those grows.

 

[Cephalotus]

Can someone explain the intended function of the 7 kWhr PowerWall....

We already have many thousands of similar systems installed in Germany. Feed in tariff for PV electricity is around 12ct/kWh, tariff for buying electricity is around 28ct/kWh.

So people want to optimize their solar energy self consumption.

This is what even a small 2kWh storage system can do in Germany (where 3-4 months have next to no solar irradiation):

http://www.sma-sunny.com/wp-content/uploads/2015/04/Kompaktspeicher-Placebo-oder-Zukunftsl%C3%B6sung-Ergebnisse-aus-einem-Jahr-Felderfahrung.pdf (sadly only in German)

For a typical German household 7kWh is larger than it would be economical wise and 2kW will keep the batteries alive for a much longer time (=less heat), which is much more important than maximizing self production rate from 80% to lets say 82%.

Why someone would buy such a storage system in the US with is net metering solar tariff is beyond my imagination. maybe because Tesla is written o it? maybe Apple could also sell a storage system? Make it white with a nice apple logo and you will have 10.000 customers in the first day?

 

[Hillhater]

Same here (Italy).
So the 2kW of power is just meant to cover most of the standard consumption, as any peak will be covered by the grid, which is already there (peaks are free, in a sense).

Here in Italy most houses get 3kW max power from the grid, hence 2kW would cover most of the use cases..

2 points..
A) are you sure of that 3 kW figure ?
.....I could understand it as an " average" daily consumption, ..but not as a max figure.
Heating, A/C, hot water, ?..just using a hair dryer whilst making a coffee, would max out that 3kW.
And what will you guys do when EV"s do become the norm and need charging ?

B) "...if any "peaks". (Power shortages ?)...are to be covered by the grid, ..why bother with this battery anyway ??

Oh, and robot vacs are next to useless in any real situation, and a 1 kW vac is equally a toy compared to a 2.5 kW vac which is still the norm' in my world.

 

[Hillhater]

Same here (Italy).
So the 2kW of power is just meant to cover most of the standard consumption, as any peak will be covered by the grid, which is already there (peaks are free, in a sense).
..

[
, how can we power all those air-conditioners during the summer peak demand hours? Its called "time shifting", when the power walls charge up at night (when the coal plants are running at an idle speed), and then put electric back into the grid during 11AM-5PM peak heat hours...

Thats the first customer model, the second is "local net-metering" where houses that agree to have solar-PV panels mounted on their roof will get a price break on the install and monthly electrical use. houses with the solar panels and Tesla walls will feed the local grid during peak demand.
.

Why someone would buy such a storage system in the US with is net metering solar tariff is beyond my imagination. maybe because Tesla is written o it? ?

Well, not much consensus there !
Infact several totally opposing views
It sounds like there "May" be a application in some cases in Europe,.. But I doubt that is the market Tesla were aiming for.
( sorry, I could not translate that PDF !)
SM?.. The "peak smoothing" idea is the function of the large " Power pack" modules installed by utility Co's .
Don't believe the sales pitch... There is no way a domestic installation feeding network peaks on "Net metering" would ever be allowed to be economical whilst the utilities are setting the tariffs .( even tesla said as much )
And anyway, ar'nt those "peaks" Or power shortages.. By definition, exactly when you might need the extra power yourself ?

 

[speedmd]

We don't have or need AC here in the berkshires. Two weeks of hot summer weather most years. Makes no sense to have an expensive battery if your power never goes out and you get near full credit on the power you send to the grid, but this swap deal will not last for long. You can bet on that. Having a battery that can help with high demand appliances is part of the value to the power system as a whole. Eliminating the spikes in demand by acting as a supply buffer when you need to light up the the big TIG welder to fix your bike frame or rapid charge your EV.

 

[quamau]

Hillhater: yes, I am positive of the 3kW max power limit. In detail: the limit is 3.0kW but the meter actually breaks at 3.3kW (10% tolerance); ii) there are grace periods, like 20% excess allowed for 1', the slightest excess of 0.x% will cut the power after 15'; iii) it is of course possible to have more power on your household, but this costs a lot: say 50% more on the fixed costs and 30% more for each kWh used. A rough estimate is that one fourth - one fifth only of the households use higher power.

I personally regard this system of pushing towards low power as a very effective way of keeping the country system under control. From an environmental viewpoint, power consumption brings about its costs, similarly to energy consumption.

Will we need extra power? That's too general a question. I personally don't, so far, although I have a cooking stovetop that by itself has 7+kW peak power consumption; I have lightweight ebike batteries only to recharge, heating is not electric, hot water is not electric, conditioning is not needed thank to thermal design of building, lightning is modern and low-power, my vacuum bot is extremely satisfaying, way more than the conventional one. The only anticipated scenario where I'd need more power is for an electric car. In this case.. I'd buy a powerwall!

 

[Hillhater]

OK, I see the logic, to encourage reduced electricity demand, but I don't necessarily agree that it's a smart idea.
All it's doing is forcing people to use other energy sources, (gas, oil, coal, wood,) or , ideally, install solar.
That is government opting out of it's elected obligations and forcing the public to make compromises and find solutions to energy shortages, when Utility companies should be investing in mass solar, wind, geothermal, mass storage, etc and other renewable clean, energy sources.
Electricity is still (potentially) the cleanest source of renewable energy...it makes sense to encourage its use in preference to other options.
You would need a few of those PowerWalls to feed your cooker , let alone charge the EV. ,

 

[speedmd]

Age old argument to centralize or decentralize power. With roof top PV cells coming of age, is it better to invest in centralized power plant / mass distribution grid networks with all its waste or store it where it is used / needed over the course of the average day. We are nearing a suitable cost trade off. Still a bit out of reach, but with demand charges constantly going up, battery prices going down and durability increasing, it may not be long before it is cost effective. Industrial demand charges are out of sight in our area, and most small shops that run large machines sporadically would benefit in short order from a large bank of these.

 

[Hillhater]

. Industrial demand charges are out of sight in our area, and most small shops that run large machines sporadically would benefit in short order from a large bank of these.

Yes, energy cost in industry is a major factor, . Tariffs for electricity , gas, etc are usually structured to encourage constant reviews of energy consumption. Just as PFC has been a focus, battery "peakers" should be high on the list for consideration.
But likely the large "PowerPack" modules !

 

[arkmundi]

Massachusetts has the most aggressive RPS in the nation along with the RGGI to manage block purchases of REC's for compliance. After years of considering rooftop solar, I may take the plunge. I have long felt that I had a great supplier in MassEnergy and have been on their 100% wind energy plan. Then earlier this year MassEnergy sent out a plea for their customer base to go solar with a plan they had worked out with Direct Energy Solar. Since its grid-tied net-metering, I don't need a Tesla Powerwall. Unless, that is, I want to detach from the grid and go mobiling around. And take the Google challenge of batter-powered EV AS grid storage.

 

[Joseph C.]

The Powerwall doesn't make economic sense for America or Canada but it should work well in Germany, Switzerland etc. Though you'd need at least two of them to make it work for most people. A kettle alone uses 3KW, an immersion heater 3.5KW. Power showers would be completely out of the question at up to 11KW. A fairly energy efficient house will only use about three or four KW hours a day if they're being heated by alternatives to electricity.

The Powerpack, on the other hand, really does make financial sense for utilities. At 25k a unit that works out at about 5 cent per KW/hr over 5,000 cycles for 15 years (the specs Musk gave). If the utilities can live with a 20 per cent reduction for another thousand cycles that price drops to 4 cent per KW/hr. If you use just 80 per cent per cycle the numbers go to 6 and 5 cent respectively.

Right now the cells are probably costing roughly 150 dollars per KW/hr - so the packaging and other elements is worth about 10,000 per pack minus the battery connections. If the utilities don't have to pay for replacing the packaging and thermal management in 15 years time that will be an even bigger saving for them.

In 15 years from now the price for a Powerpack will probably be $10,000 plus inflation. That's two cent per KW/hr for 5,000 cycles if you go with a completely new replacement pack - one cent if you just replace the battery.

 

[Joseph C.]

I hope those figures are comparing apples to apples, because that $250 /kWhr figure is pure cell cost, not installed cost.
The 7 kWhr home PowerWall module has been quoted as costing $7+ k installed with necessary ancillaries !
That's over $1000 per kWhr

SolarCity is only offering the bigger Powerwall to customers buying new rooftop solar systems. Customers can prepay $5,000, everything included, to add a nine-year battery lease to their system or buy the Tesla battery outright outright for $7,140. .

Obviously the commercial/ industrial systems won't have that pricing, but it won't just be cell cost either !

Treehouse are quoting 3,000 as their retail price. Solar City are notorious for having very large mark-ups if someone pays $7,140 for $3,000 battery they need their head examined - they are being ripped off. It should only cost an extra 500 or to install it. It's just a question of drilling some holes, getting two people to lift it into place and having an electrician connect it to the solar panel set up. An hour's work at most for people who will have installed hundreds of the things.

The raw cell cost is about 1K for 7KW/hr. $1,155 if you go by the now outdated price by Credit Suisse of $165 per KW/hr in their 2014 report.

 

[megacycle]

I'm confused about the operation of the Powerwall.
Does the dc output of the PV panels feed into the powerwall at high voltage dc and the powerwall output feed into the consumers solar inverter?

 

[Joseph C.]

I'm confused about the operation of the Powerwall.
Does the dc output of the PV panels feed into the powerwall at high voltage dc and the powerwall output feed into the consumers solar inverter?

Looking at Tesla's figure of 92 per cent efficiency, I think that means that it bypasses the inverter but the numbers don't look right either way unless Tesla has rounded up.

If you look at Solar Edge's website the solar panels are connected to Power Optimisers which are DC to DC and 98.8 per cent efficient - then they do to a 97.6 per cent efficient inverter.

98.8 to 98.8 to 97.6 is 95.8 per cent efficient. But if you go through the Inverter I think you add two extra processes DC to AC and AC to DC again bringing the total down to 91 per cent but they might bypass the inverter steps.

By the way if Tesla used the peak efficiency for the Power Optimisers the number adds up fairly close to 92 per cent if you don't bypass the inverter.

99.5 = DC-DC > 97.6 DC-AC > 97.6 AC-DC > 99.5 DC-DC > 97.6 DC-AC total loses 8.2 per cent - round total efficiency of 91.8 per cent. I think they go through the inverter but I also think if that is the case the real efficiency is 90.4 per cent not 92.



Solar Edge are an official partner for the Powerwall stuff.

http://www.solaredge.com/groups/powerbox-power-optimizer

 

[megacycle]

I think that means that it bypasses the inverter

Solar Edge are an official partner for the Powerwall stuff.
http://www.solaredge.com/groups/powerbox-power-optimizer

Yes I've been installing solar edge products here in Australia and they're great, due to the really long strings we can now do with optimization, individual monitoring and output protection is really cool.
I've heard powerwall will be compatible with a range of inverters, but I'm unsure how, the powerwall must have a compatible internal high voltage inverter/charger in its package, as most solar inverters sold, need another inverter/charger with automatic switching which detects the grid and can keep the solar inverter feeding the house in a power outage, it's called a.c. coupling.

 

[megacycle]

This is the configuration ive been used to seeing-
https://www.google.com.au/search?q=sp+go+pro+grid+backup&biw=360&bih=592&noj=1&source=lnms&tbm=isch&sa=X&ei=yPZUVcf-BuTAmwXFroCgDA&ved=0CAcQ_AUoAQ#imgrc=hK3yVojOsZ5OqM%253A%3BGQyFqBGvEkqeQM%3Bhttp%253A%252F%252Fwww.glsolar.com.au%252Fcmsimages%252FHybrid%252520architecture%252520Retro%252520fit.png%3Bhttp%253A%252F%252Fwww.glsolar.com.au%252Foff-grid-hybrid-systems.asp%3B805%3B616
The configuration maybe more like this, with integrated high voltage pv charge controller.
http://uvpower.com.au/hybrid/

 

[MitchJi]

I'm confused about the operation of the Powerwall.
Does the dc output of the PV panels feed into the powerwall at high voltage dc and the powerwall output feed into the consumers solar inverter?

Hi,

The Powerwall comes with a DC-DC Convertor. You are correct about it using the solar systems AC Invertor.

 

[megacycle]

The Powerwall comes with a DC-DC Convertor. You are correct about it using the solar systems AC Invertor.

But it says it can only deliver 2kW, so in ac coupled mode, it must have a good supply of solar output boosting it, as 2kW, generally, wouldn't be enough for a family household, without energy management, or seperate essential loads board, when the system transfers over to 'off grid'.
Could see this might work ok during daylight hours with good sun, but at other times, it couldn't transfer over without load management.
I can't find any real in depth operational details on this gear, to work it out.

 

[Joseph C.]

The Powerwall comes with a DC-DC Convertor. You are correct about it using the solar systems AC Invertor.

But it says it can only deliver 2kW, so in ac coupled mode, it must have a good supply of solar output boosting it, as 2kW, generally, wouldn't be enough for a family household, without energy management, or seperate essential loads board, when the system transfers over to 'off grid'.
Could see this might work ok during daylight hours with good sun, but at other times, it couldn't transfer over without load management.
I can't find any real in depth operational details on this gear, to work it out.

I wonder how long it can put out a peak of 3.3KW for? I think you'd need at least three of them even for energy efficient homes if you wanted to go off-grid.

 

[liveforphysics]

In most solar setups, the DC-DC is just sized to handle the amount of solar pannels feeding it to charge. The inverter is powered by a tap to the pack. A pity we don't have a good schematic or pics, but I bet this can be setup the same way.

 

[megacycle]

I wonder how long it can put out a peak of 3.3KW for? I think you'd need at least three of them even for energy efficient homes if you wanted to go off-grid.

I think 2 might do for an average sized household, that has energy efficient appliances and alternate methods of heating and cooling using gas and efficient aircon, like evaporative or efficient reverse cycle, if the peaks can sustain the 6.6kW for half hour or more, that's a lot of juice.