Worth switching to net "time-of-use" metering for grid-tie solar system in NY (ConEd)

[ButchDeal]

I believe it was said in the unveiling that they can be charged directly via DC, for slightly higher efficiency. The rumor is, the solar cells are going to push high voltage DC into the powerwall 2 and it's going to charge and do the inversion, no need for a dedicated solar inverter anymore! It's also the only way a grid tied setup could charge a powerwall, if the powerwall was completely discharged. Unless there's some "emergency jump start capacity" that lets you fire up the inverter using what's left of the battery when the sun comes up. That would be cool.

I'm hoping the $1,000 install for the powerwall covers the auto transformer and all with Tesla hardware. I'd just need to make my SE7600 able to put DC current into the battery, let it handle control of AC power in and out of the house. Who knows until the installer comes out and shows me options though.

True, more reason to do it in DC, if it doesn't cost thousands extra. But it's good to know the AC-DC-AC loss is single digit percentages, I thought it would be more. Thanks for that.

What do you mean by dedicated solar inverter. Al DC coupled bimodal systems work with only one inverter and the powerwall 1 storedge solution only has one inverter.
The powerwall 2 is an AC coupled solution that was mentioned will work with most existing solar inverters.
You can charge the powerwall two via AC coupling from any solar inverter. Your statement about e only way to charge makes no since, even a DC coupled system will. Not start if the battery is dead. The emergency jump start is with a generator BTW.

[nevetsyad]

It is not evident that the powerwall 2 has a DC to DC capability. Further the solaredge inverter is 98% efficient and likely the powerwall 2 inverter is close. The lose is in the chemical transition from electromechanical energy ( electricity ) to chemical stored energy in the battery and back. So you would have a smaller efficiency gain by using DC to DC vs AC to AC to DC .

BTW it is $1500 in parts to upgrade the SE7600-US to the storedge ( SE7600-USS) but even more to upgrade it to backup capable with the auto transformer, emergency panel and wiring, and consumption meter.


What you are talking about is a DC coupled solution with powerwall 1 vs an AC coupled solution with powerwall 2

I am not a big fan of AC coupled solutions of any type due to over complexity, multiple equipment manufacturers ( some do not support the solution), and excess wear to the equipment from the poor throttle ability of the designs.

DC coupled solutions are simpler, and much more easily controlled.

I believe it was said in the unveiling that they can be charged directly via DC, for slightly higher efficiency. The rumor is, the solar cells are going to push high voltage DC into the powerwall 2 and it's going to charge and do the inversion, no need for a dedicated solar inverter anymore! It's also the only way a grid tied setup could charge a powerwall, if the powerwall was completely discharged. Unless there's some "emergency jump start capacity" that lets you fire up the inverter using what's left of the battery when the sun comes up. That would be cool.

I'm hoping the $1,000 install for the powerwall covers the auto transformer and all with Tesla hardware. I'd just need to make my SE7600 able to put DC current into the battery, let it handle control of AC power in and out of the house. Who knows until the installer comes out and shows me options though.

True, more reason to do it in DC, if it doesn't cost thousands extra. But it's good to know the AC-DC-AC loss is single digit percentages, I thought it would be more. Thanks for that.

[ButchDeal]

I like the idea of charging with DC. The Powerwall 2 has a 90% efficiency AC-DC-AC again with it's onboard inverter and charger. If I charge it DC-DC, then let it output AC, I should gain ~5% efficiency. Plus the fact that it will charge via DC if it goes completely empty at night and can't turn on again in the morning.

What I don't like is that it's about $1,500 in parts to upgrade the SE7600-US to the USS that can charge a Powerwall via DC. I'm sure that will be at least $2K installed. But again, I really do love the idea of being able to start the system with no line current and a dead battery. Will have to see what quotes I get when they start shipping the hardware.

It is not evident that the powerwall 2 has a DC to DC capability. Further the solaredge inverter is 98% efficient and likely the powerwall 2 inverter is close. The lose is in the chemical transition from electromechanical energy ( electricity ) to chemical stored energy in the battery and back. So you would have a smaller efficiency gain by using DC to DC vs AC to AC to DC .

BTW it is $1500 in parts to upgrade the SE7600-US to the storedge ( SE7600-USS) but even more to upgrade it to backup capable with the auto transformer, emergency panel and wiring, and consumption meter.


What you are talking about is a DC coupled solution with powerwall 1 vs an AC coupled solution with powerwall 2

I am not a big fan of AC coupled solutions of any type due to over complexity, multiple equipment manufacturers ( some do not support the solution), and excess wear to the equipment from the poor throttle ability of the designs.

DC coupled solutions are simpler, and much more easily controlled.

[nevetsyad]

Is there something wrong with charging via DC? All DC coupled systems work that way.

The storedge has the disconnect part, yes so you would have to add disconnect method for the powerwall 2.
Both the storedge and the powerwall 2 will need an auto transformer to give you 120v from the 240v inverters.

I like the idea of charging with DC. The Powerwall 2 has a 90% efficiency AC-DC-AC again with it's onboard inverter and charger. If I charge it DC-DC, then let it output AC, I should gain ~5% efficiency. Plus the fact that it will charge via DC if it goes completely empty at night and can't turn on again in the morning.

What I don't like is that it's about $1,500 in parts to upgrade the SE7600-US to the USS that can charge a Powerwall via DC. I'm sure that will be at least $2K installed. But again, I really do love the idea of being able to start the system with no line current and a dead battery. Will have to see what quotes I get when they start shipping the hardware.

[ButchDeal]

Only if you want to charge it via DC. The Powerwall 2 can connect to AC exclusively and charge/discharge into it on its own. However, if I go that route, and my battery dies at night, my solar won't start generating in the morning.

https://electrek.co/2016/10/28/tesla...inverter-5500/

Also, the Powerwall 2 will have to have some sort of auto transformer or whatever installed so it can cut off outside AC if the line doesn't have current. Before, that was done with SolarEdge optional hardware.

Is there something wrong with charging via DC? All DC coupled systems work that way.

The storedge has the disconnect part, yes so you would have to add disconnect method for the powerwall 2.
Both the storedge and the powerwall 2 will need an auto transformer to give you 120v from the 240v inverters.

[nevetsyad]

The storedge is capable but requires more parts to configure it for backup. It will be the same for the powerwall 2.

Only if you want to charge it via DC. The Powerwall 2 can connect to AC exclusively and charge/discharge into it on its own. However, if I go that route, and my battery dies at night, my solar won't start generating in the morning.

https://electrek.co/2016/10/28/tesla...inverter-5500/

Also, the Powerwall 2 will have to have some sort of auto transformer or whatever installed so it can cut off outside AC if the line doesn't have current. Before, that was done with SolarEdge optional hardware.

[nevetsyad]

I might be wrong, but I believe the Powerwall battery (or at least the inverters that work with it) is not capable of running as backup power during an outage.

It includes a 7kW peak output, 5kW sustained, inverter onboard. If it's online, my SE7600 will put out 5-6kW during a good day also. I can optionally upgrade my SE7600 so that it charges the battery directly via DC.

[ButchDeal]

I might be wrong, but I believe the Powerwall battery (or at least the inverters that work with it) is not capable of running as backup power during an outage.

The storedge is capable but requires more parts to configure it for backup. It will be the same for the powerwall 2.

[solarix]

I might be wrong, but I believe the Powerwall battery (or at least the inverters that work with it) is not capable of running as backup power during an outage.

[nevetsyad]

Again, my primary goal is being able to keep the furnace going during a winter storm, keep the fridge going, possibly run the AC in the summer while the sun is out. If I can save a grand or two over the battery's life by load shifting, that's just gravy.

They installed a few hundred of them (I think) in Australia and there's some very happy owners down there. Primarily using them for shifting solar production for peek time use. http://mobile.abc.net.au/news/2016-0...orking/7664450

The new one is a joint venture with Panasonic, using new cells, and much more efficient battery packs, allowing them to double the energy in roughly the same size package. I think they'll deliver on time, it's pretty much all the gigafactory 1 is building right now.

[J.P.M.]

I'm hoping the smart meter they just installed will let me look into when I use power. I'll set power hungry loads to run from 1-5AM, and see how much I can shift to then. The AC is my big concern, if it's going to use 30kWh in the evenings, or 50kWh during a hot summer Saturday while we're home, that could kill all saving. Actually, solar may be up to 40kWh for a summer day, and if I can shift over 10kWh from super off peak, even 50kWh of HVAC on a horrible summer day may not be too bad. I could end up paying $.05 per kWh for 99% of my needs.

Have you seen the specs and pricing for the Powerwall 2? With the included inverter, it's pretty much half the price of anything else on the market, maybe a quarter if you try to match it for capacity. I hate the idea that during an emergency, my solar just sits up there doing nothing, unable to charge my EVs or even run the furnace fan to heat the house.

I'm hoping to install another 1kW of solar with the wall, for under 10K total. The package will qualify everything for a 30% tax credit, making it cost just over 6 grand, backup power, time of use shifting, and a little extra generation. Not horrible at all.

Yes, and until I see some actual numbers from users and feedback, I consider the specs little more than vaporware. Even at that, and even if the power wall performs as advertised, I suspect that in most cases the potential savings will lead to a long payback, especially when considering most potential users are clueless about how they use energy and bereft of any ideas about reducing usage.

Before I spent $6K on anything such as a storage device, I'd want to be pretty sure of what an objective estimate (that is, from someone with no skin in the game like a peddler) of what annual savings might be before I pulled the trigger.

The key is accurate information and the ability to analyze it.

[nevetsyad]

I'd first find out if I could try T.O.U. for, say, 1 yr. as a trial period, keep good records as in a daily log of electrical use, see what it does to my bills and switch back if it doesn't pay. If that's possible, do it. Then, with a year's data in hand, see if some form of storage makes economic sense.

At this time, you have no data for informed decision making, only feelings and guesses based on wishes and hype from Musk, and likely no clue about how, or how much electricity you use.

At the end of a year, Musk's storage will get some exposure in the market, the price may be less, perhaps to the degree of a year's possible savings from using the device, and there may be competition from other products, or at least more info on product performance (or lack of it).

Right now, the power wall thing is an overpriced toy with no track record, ideal for those with more money than brains.

I'm hoping the smart meter they just installed will let me look into when I use power. I'll set power hungry loads to run from 1-5AM, and see how much I can shift to then. The AC is my big concern, if it's going to use 30kWh in the evenings, or 50kWh during a hot summer Saturday while we're home, that could kill all saving. Actually, solar may be up to 40kWh for a summer day, and if I can shift over 10kWh from super off peak, even 50kWh of HVAC on a horrible summer day may not be too bad. I could end up paying $.05 per kWh for 99% of my needs.

Have you seen the specs and pricing for the Powerwall 2? With the included inverter, it's pretty much half the price of anything else on the market, maybe a quarter if you try to match it for capacity. I hate the idea that during an emergency, my solar just sits up there doing nothing, unable to charge my EVs or even run the furnace fan to heat the house.

I'm hoping to install another 1kW of solar with the wall, for under 10K total. The package will qualify everything for a 30% tax credit, making it cost just over 6 grand, backup power, time of use shifting, and a little extra generation. Not horrible at all.

[J.P.M.]

I'm getting one for backup power. The question is, should I switch to time of use and try to gain back some of the cost by time shifting my solar generation. Or leave it charger as an emergency standby only and keep net metering.

The bulk of my non-summer use is at night, EV charging. But even summer I think charging at night and discharging during peek times would be benifitial.

I'd first find out if I could try T.O.U. for, say, 1 yr. as a trial period, keep good records as in a daily log of electrical use, see what it does to my bills and switch back if it doesn't pay. If that's possible, do it. Then, with a year's data in hand, see if some form of storage makes economic sense.

At this time, you have no data for informed decision making, only feelings and guesses based on wishes and hype from Musk, and likely no clue about how, or how much electricity you use.

At the end of a year, Musk's storage will get some exposure in the market, the price may be less, perhaps to the degree of a year's possible savings from using the device, and there may be competition from other products, or at least more info on product performance (or lack of it).

Right now, the power wall thing is an overpriced toy with no track record, ideal for those with more money than brains.

[nevetsyad]

I'm getting one for backup power. The question is, should I switch to time of use and try to gain back some of the cost by time shifting my solar generation. Or leave it charged as an emergency standby only and keep net metering.

The bulk of my non-summer use is at night, EV charging. But even summer I think charging at night and discharging during peek times would be beneficial.

[solarix]

There is no way a Powerwall will ever pay for itself.