Tesla Powerwall

[dwh]

Off-grid makes sense.

Maybe, maybe not. For less than twice the price, you can get 3.5 times the storage capacity with a forklift battery (with 7 year warranty):

http://xtrapowerbatteries.com/index.php/battery-for-cat-e20k-18-85-25.html


An average daily consumption of 5 kwh would take the Tesla battery down by 1/2, but would only take the forklift battery down by 1/7. Double the Tesla battery to get a 10 kwh daily budget, and it would take the pair of Teslas down by 1/2, but for that same cost, the forklift battery would be down by less than 1/3.

So if you don't have to carry it around and don't care that the forklift battery weighs 3,000 pounds, then it would probably be a better solution for long-term off-grid.

Plus, to charge the Tesla at 350v-450v, using MPPT, you'd probably need to rig the solar array for 600v, which is the max that most PV modules are rated for.



But also, I just noticed that the Tesla site says:

'Powerwall comes in 10 kWh weekly cycle and 7 kWh daily cycle models.'

http://www.teslamotors.com/powerwall


So the numbers are all very rough unless we know exactly how deeply they can be drained and still last 10 years...

 

[dwh]

Idk where you live but in California. HO pay anywhere between 100-900 a month in electric bills.

With a solar and battery set up. You pay a month payment usually 10-20% less than your current bill.

Your already paying for power. Why not just pay less.

Solar companies are basically power companies who sell you power for less
With a battery system. You can just about go off the grid.


Sent from my iPad using Tapatalk

Most on-grid solar leasing arrangements do NOT have batteries.

Quite a few utility companies don't even allow batteries to be used in a grid-tie solar setup. Their theory is to prevent people buying power from the grid at low rates, sticking it in a battery, and then selling it back to the grid later in the day at higher rates.

For almost all on-grid solar - the grid is the battery.

 

[Yuman Desert Rat]

WHAT do you think is going to happen when big brother starts taking a hit on tax revenues due to large numbers of people using and consuming less electricity from the taxable grid?

 

[dwh]

WHAT do you think is going to happen when big brother starts taking a hit on tax revenues due to large numbers of people using and consuming less electricity from the taxable grid?

Lemme guess...more taxes?

 

[mpinco]

WHAT do you think is going to happen when big brother starts taking a hit on tax revenues due to large numbers of people using and consuming less electricity from the taxable grid?

Ask Saudi Arabia .......... they have a recommendation.

 

[IdaSHO]

WHAT do you think is going to happen when big brother starts taking a hit on tax revenues due to large numbers of people using and consuming less electricity from the taxable grid?

Easy, you will be taxed on your energy usage, regardless of how it was generated.


Things are already changing that way for hybrid and electric cars. They are charging the taxation structure for "fuel" taxes.

Taxed by the mile.

 

[adam88]

I heard that the 7kwh daily cycle unit isn't actually 7kwh, its actually 10kw of batteries... rated to cycle at 7kwh a day. Not sure if there's any truth to that, but I heard it from several places. If its true then the 7kwh is effectively a 10kwh battery, something to keep in mind, and it can actually be cycled a full 7kwh a day. For comparison, you would need a 14kwh battery bank of normal batteries (to avoid discharging below 50%) to achieve 7kwh, assuming a daily cycle.

 

[pexic]

Hello

The above article is not well documented since the autor suppose (and make his calculations) that Accu from Tesla is Lead-Acid type .. but what if it's not Lead-Acid but LiFePo4 ?

https://www.youtube.com/watch?v=ZkMk8djVUQk

p.s. sorry for my English.

 

[mpinco]

What do you really get for a $7,000 Tesla Powerwall home battery?

"........That future, though, is not close. "Off-grid electricity supply will remain punishingly expensive for the foreseeable future," wrote Bernstein Research analyst Hugh Wynne in a recent report.

For now, and likely for several more years, Tesla's home battery, called a Powerwall, is a backup power source not much different from the generators for sale at any hardware store. It will keep the lights on and the refrigerator cold during a blackout, but it doesn't run power-hungry devices like air conditioners or clothes dryers.

At an installed cost of about $7,000, it's an appliance that makes very little financial sense for most people.......

......The price to go completely off the grid is even higher because that would require a rooftop solar system bigger than what is now usually installed, and at least two Powerwall batteries. That kind of system would cost $96,000 without subsidies, about 74 years of electric bills for an average US customer, calculates Bernstein Research's Wynne. Even assuming the cost of solar and batteries declines by 80 percent in the coming years and that it will be subsidized by clean-energy incentives, the system would still cost 2.5 times more than buying electricity from the grid, according to Wynne......."

 

[Dan Grec]

......The price to go completely off the grid is even higher because that would require a rooftop solar system bigger than what is now usually installed, and at least two Powerwall batteries. That kind of system would cost $96,000 without subsidies, about 74 years of electric bills for an average US customer, calculates Bernstein Research's Wynne. Even assuming the cost of solar and batteries declines by 80 percent in the coming years and that it will be subsidized by clean-energy incentives, the system would still cost 2.5 times more than buying electricity from the grid, according to Wynne......."[/I]

People who want you to continue to consume are always going to spout this nonsense. It's simply not true.

My Parents just had 5kW of solar installed, with inverter and all for $10,000. (the government later re-reimbursed them $5k of that, but that's not relevant here)
Over the last 3 months, on average they're using ~10kW hours of electricity for their 4 bedroom house, and generating about ~20kW hours of electricity from solar.
Their power bills are now negative (i.e. the power company is paying them).

Add a powerwall for another ~$7k, and they'd be paid even more, because they would never take power from the grid at night, and only ever charge the powerwall and put energy back into the grid during the day.

-Dan

 

[mpinco]

.....My Parents just had 5kW of solar installed, with inverter and all for $10,000. (the government later re-reimbursed them $5k of that, but that's not relevant here).....

Hmmmmm ...........

How much does a typical residential solar electric system cost?

The average residential system is 5 kW or 5,000 watts.

System cost 5,000 w x $5.50/watt $27,500

Federal tax credit 30% x $27,500 $8,250

Total after tax credit $19,250


How Much Does it Cost to Install Solar on an Average US House?

".....At the time of this writing, the installed cost of solar panels was between $7-$9 per watt: A 5 kW system would cost around $25,000-$35,000. Many utility companies offer incentives, and some subsidize as much as 50% of system costs. Even at half the cost, though, a system that generates an average $75 of electricity per month could take a long time to pay for itself.

For example: A system that costs $18,000 has a payback period of about 20 years. The cost of a solar panel today is around $3 per watt, and the extra cost of installation brings costs up to $5- $6 per watt.......

......Assuming that installation and auxiliary equipment costs can be reduced to around $1 per watt, then a 5 kW system may cost as little as $10,000........."

Labor Costs of Installing Solar Panels

The total costs of a typical solar panel system of 5kW (15 – 25 solar panels), is typically somewhere around $30,000. According to Lawrence Berkley National Laboratory (LBNL), average cost of labor is $0.59/W – about 10% of total system costs ($6.19/W).[1] You should expect to pay around $3,000 in labor costs for a 5kW solar system.......





Just a quick review but looks like solar cost are in the $6-$9 per watt range, then add in the PowerWall at $7K, plus financing, and your in the $35K to $45K range or ~$8K per kW




How Fast Are The Costs Of Solar Really Coming Down?

.....Less Than Meets The Eye

Claims that solar will continue to see rapid global growth rates are largely predicated upon assumptions regarding sustained subsidies and cost declines. Feed-in tariff support in Germany has fallen from $0.50/kWh in 2000 to below $0.16/kWh in recent years. The installed cost of solar in Germany has fallen correspondingly, dropping from above $6500/kW in 2006 to approximately $2250/kW today.

Germany today has the cheapest solar in the world, and the country's FIT program has been instrumental in driving these cost declines. This, unfortunately, has limited impact to countries outside of Germany. That is because two-thirds or more of the installed cost of residential solar systems are soft costs, unrelated to the cost of the modules. Owing to costs related to permitting, installation, supply chains, mounts, inverters, and other non-module costs, solar PV systems cost as much as two to three times more in other countries than they do in Germany. In the United States, the installed costs of residential solar remain about $5000/kW, according to GTM Research and the Solar Energy Industry Association. According to the International Renewable Energy Association (IRENA), most major solar markets have installed costs for residential solar significantly higher than those in Germany. In short, German policies have made solar's soft costs much cheaper in Germany, but they haven't done so for the rest of the world.

To date, there is little evidence that it is possible to rapidly reduce domestic solar soft costs without spending a decade subsidizing production and installation as Germany has.........."

 

[dwh]

Their power bills are now negative (i.e. the power company is paying them).

Which utility company is that? I was unaware that any were actually paying money out to customers.

Most simply issue a credit to the account for any excess. Generally, this credit builds up for a year and then once a year the account is reset to zero.

In other words, if you send more to the grid than you take from the grid, they keep the extra.

For this reason, when installing grid-tie co-generation, it's normal to size the system to generate however much the building uses, but it's not financially justifiable to install more than that.



I would be interested to know which utility companies have upgraded their billing systems to where they actually pay money out to customers for the excess rather than just keeping it.

 

[dwh]

http://emp.lbl.gov/publications/tra...led-price-photovoltaics-united-states-1998-20

 

[mpinco]

FYI ...... haven't had chance to critique the math.

Why Tesla's Batteries Won't Work For Roof-Top Solar

Submitted by Euan Mearns via OilPrice.com,

In How Much Battery Storage Does a Solar PV System Need? I assumed that the rooftop PV system would generate just enough power to fill annual domestic demand and that the surplus power generated in summer would be stored for re-use in the winter in Tesla batteries. The result was an across-the board generation cost of around $35/kWh. Clearly the Tesla battery storage option isn't economically viable, or at least not under the scenario I chose.

As Phil Chapman and others pointed out in comments, however, this is not the only way a domestic solar PV system can generate enough year-round power to allow a household to go off-grid. Another is to overdesign the system so that it's large enough to fill demand in winter when solar output is at a minimum and simply curtail the excess power generated in summer. How does this “no storage” option pan out?

To evaluate the no-storage case I use the same four scenarios as for the battery storage case (Equator, 20, 40 and 60 degrees north latitude) and add another (50 degrees north latitude) to provide more detail. ..........

 

[dwh]

FYI ...... haven't had chance to critique the math.

Why Tesla's Batteries Won't Work For Roof-Top Solar

Submitted by Euan Mearns via OilPrice.com,

In How Much Battery Storage Does a Solar PV System Need? I assumed that the rooftop PV system would generate just enough power to fill annual domestic demand and that the surplus power generated in summer would be stored for re-use in the winter in Tesla batteries. The result was an across-the board generation cost of around $35/kWh. Clearly the Tesla battery storage option isn't economically viable, or at least not under the scenario I chose.

As Phil Chapman and others pointed out in comments, however, this is not the only way a domestic solar PV system can generate enough year-round power to allow a household to go off-grid. Another is to overdesign the system so that it's large enough to fill demand in winter when solar output is at a minimum and simply curtail the excess power generated in summer. How does this “no storage” option pan out?

To evaluate the no-storage case I use the same four scenarios as for the battery storage case (Equator, 20, 40 and 60 degrees north latitude) and add another (50 degrees north latitude) to provide more detail. ..........

Yea, his premise for the original article - storing enough power in batteries to last through the winter - was goofball in the extreme. Fortunately someone pointed out in the comments for that original article that you can just upsize the array to get the job done a whole lot cheaper than buying enough battery to get through the winter.

His second article - the one you linked to - is also a bit goofball. He's basing his calculatiions on yearly average, and calling it a "no-storage case" but tossing in a battery as well:

"And while I refer to it as the no-storage case there will inevitably be times when the rooftop solar system won't generate enough energy to meet household demand, meaning that some backup storage will be needed. To supply it I add one 10kWh Tesla battery storage unit, which would be capable of filling demand for at least one powerless winter night, and just in case I also add a 3kW backup gasoline generator."

The reason that's goofball, is exactly because of what he put there in bold: "there will inevitably be times when the rooftop solar system won't generate enough energy to meet household demand, meaning that some backup storage will be needed".

I would say to him, "Well yea...no ******** Sherlock. That's gonna happen every freaking night!"


His math is correct, but his basic screw up, is ignoring daily use and instead focusing on annual use. The people actually living in the building and using the system can't do that. They need power to get through the night, every night.


A "no-storage case" is not even possible in the real world using solar. To get through the night, you've either got to store the excess in a battery, or sell it to the grid so you can buy it back at night.