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

[azdave]

If your production cover near 100% of your demand, then it's a no-brainer that you don't want to use TOU plan.

I know I'm quoting an old reply but check with your utility if you can even get a basic plan if you generate power on site.

In the case of SRP in Phoenix, they now prevent anyone with on site generation from signing up for anything but the E-27 TOU plan with a new demand charge applied too. All the other price plan choices are not allowed unless you buy all of your power through SRP.

[nevetsyad]

Has anyone run these numbers again, but with a Powerwall 2 installed? Charge 13kWh during super off peak, discharge in the morning before the sun is fully up. Charge off the sun while everyone is at work. Discharge/be assisted by solar until peek times are over Could end up with 13kWh solar banked for peek times, and 13kWh purchased during super off peek, used during peek. Plus, backup power during a storm or emergency.

Thoughts?

[solarix]

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

[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.

[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'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 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]

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.

[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.

[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.

[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.

[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.

[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]

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]

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.