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PowerWall Without Solar?

swedge

Member
May 12, 2020
67
53
Oakland, CA
Does anyone here have a PowerWall without solar? I want to know if the Time Based, Cost Saving mode is available in such a system, and how it behaves.

My guess is that PowerWall would charge from the grid beginning at the end of peak (or partial peak) periods, until it is fully charged. Then it waits untill peak period starts, when it begins to discharge at the same rate the house consumes power, making the draw from the gird go to zero. It would continue discharging until it gets down to the reserve level or the peak period ends. This would allow the customer to time-shift his draw from the grid to off-peak times, saving him money and reducing peak demand on the grid, a win-win situation, as well as providing backup during all but extended grid outages. This is my guess, but Tesla and installers have been unable able to confirm this, because there are so few non-solar customers.

I ask this because a friend, who is not able to get solar, is considering a PowerWall, and asked me to help him calculate the savings he could expect with a PW under the various time-of-use tariffs available to him.

I do have solar, and PowerWall charges only from solar, except when Storm Watch is active when it charges from the grid. On sunny days here in October, our solar production is more than enough to fully charge the PW and thus allow us to use gird power only during off-peak hours. Cloudy or short winter days will result in inadequate charging, of course, and hence some peak price consumption.

I would appreciate any feedback on this, especially from someone with experience or specific knowledge of non-solar installations.

Thanks,
SW
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,170
9,027
Riverside Co. CA
I believe @HankLloydRight might have a powerwall without solar. Tagging him here to see if thats the case. I believe powerwalls without solar can charge off peak and discharge during peak to reduce peak load, but not sure how "the maths" pencil out as far as how long would it take to save the roughly 10-11k it would take to buy and get a single powerwall installed.

There would also be no tax credit for a powerwall installed without solar, so the purchaser would have to bear the full cost. I doubt it makes sense financially, unless one was getting a free referral powerwall (or powerwalls), which is what I believe @HankLloydRight has. That is just a guess at the math. Let us know how it pencils out.
 

swedge

Member
May 12, 2020
67
53
Oakland, CA
I believe @HankLloydRight might have a powerwall without solar. Tagging him here to see if thats the case. I believe powerwalls without solar can charge off peak and discharge during peak to reduce peak load, but not sure how "the maths" pencil out as far as how long would it take to save the roughly 10-11k it would take to buy and get a single powerwall installed.

There would also be no tax credit for a powerwall installed without solar, so the purchaser would have to bear the full cost. I doubt it makes sense financially, unless one was getting a free referral powerwall (or powerwalls), which is what I believe @HankLloydRight has. That is just a guess at the math. Let us know how it pencils out.
JJ, Thanks, I hope we hear from HLR.

Regarding the math, in my friend's case, the PW is nearly fully funded by SGIP's "Equity Resiliency Budget" an amazing California rebate program, the same program which funded my PW. "Free" makes the economics a very different proposition!
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,170
9,027
Riverside Co. CA
JJ, Thanks, I hope we hear from HLR.

Regarding the math, in my friend's case, the PW is nearly fully funded by SGIP's "Equity Resiliency Budget" an amazing California rebate program, the same program which funded my PW. "Free" makes the economics a very different proposition!

Absolutely. Free (so referral, or equity and resilliency) makes a ton of sense. Does that plan also help with solar?
 

EinSV

Active Member
Feb 6, 2016
4,328
21,513
NorCal
Does anyone here have a PowerWall without solar? I want to know if the Time Based, Cost Saving mode is available in such a system, and how it behaves.

My guess is that PowerWall would charge from the grid beginning at the end of peak (or partial peak) periods, until it is fully charged. Then it waits untill peak period starts, when it begins to discharge at the same rate the house consumes power, making the draw from the gird go to zero. It would continue discharging until it gets down to the reserve level or the peak period ends. This would allow the customer to time-shift his draw from the grid to off-peak times, saving him money and reducing peak demand on the grid, a win-win situation, as well as providing backup during all but extended grid outages. This is my guess, but Tesla and installers have been unable able to confirm this, because there are so few non-solar customers.

I ask this because a friend, who is not able to get solar, is considering a PowerWall, and asked me to help him calculate the savings he could expect with a PW under the various time-of-use tariffs available to him.

I do have solar, and PowerWall charges only from solar, except when Storm Watch is active when it charges from the grid. On sunny days here in October, our solar production is more than enough to fully charge the PW and thus allow us to use gird power only during off-peak hours. Cloudy or short winter days will result in inadequate charging, of course, and hence some peak price consumption.

I would appreciate any feedback on this, especially from someone with experience or specific knowledge of non-solar installations.

Thanks,
SW

This is a bit OT but has your friend looked into solar to go with the Powerwall?

It is so cheap -- and California electricity rates so expensive -- that solar+Powerwall will very likely provide cheaper energy than PG&E (especially if s/he is getting a subsidy on the PW). And the savings are immediate if s/he finances it (electricity savings > monthly payment for solar+Powerwall).

Also provides added energy security (more protection against longer blackouts than Powerwall alone).
 

HankLloydRight

No Roads
Jan 18, 2014
12,893
10,891
Connecticut
I'm actually in an interesting transition right now, so this discussion is timely.

As far as I know, PW without solar can not use TOU rates to power shift. But I could be wrong. (I am) The reason I don't know this for sure is that my power company, Eversource, did not offer residential TOU rates. (Well that's not entirely true, they have a Variable Peak Pricing, but the rates change daily and was complex). It wasn't as simple as an on-peak price vs off-peak price. If Eversource did offer a simple residential TOU rate, I would have pursued power-shifing further. I'm pretty sure when buying a Powerwall from Tesla, if you don't have solar, it makes it clear that the only use of PW is for grid outages, which was how we used it.

I do know there is a web interface for the powerwall where these settings may exist. There is no facility in the Tesla app to enable/disable a TOU feature (may vary if you also have solar). See next post.

But I just moved into a new area where the power company here does offer TOU rates $0.38 peak, $0.167 off peak) . But I also have a new solar order placed with Tesla (8.84kw), which includes moving my existing PW to my new home, plus one new additional referral powerwall. I hope the combination of TOU rates and 2 PWs will allow me to entirely avoid the on-peak rates. I think the way it will work is that the PWs will grid charge during off-peak hours, and during peak hours the house will run on solar+PWs. The solar array isn't large enough to run the house and charge the PWs for use during off-peak hours.
 
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HankLloydRight

No Roads
Jan 18, 2014
12,893
10,891
Connecticut
Geeze, now after I wrote all that, it does look like PW w/o Solar allows TOU powershifting in the app.

So there you go.

upload_2020-10-15_21-33-11.png
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,170
9,027
Riverside Co. CA
I'm actually in an interesting transition right now, so this discussion is timely.

As far as I know, PW without solar can not use TOU rates to power shift. But I could be wrong. The reason I don't know this for sure is that my power company, Eversource, did not offer residential TOU rates. (Well that's not entirely true, they have a Variable Peak Pricing, but the rates change daily and was complex). It wasn't as simple as an on-peak price vs off-peak price. If Eversource did offer a simple residential TOU rate, I would have pursued power-shifing further. I'm pretty sure when buying a Powerwall from Tesla, if you don't have solar, it makes it clear that the only use of PW is for grid outages, which was how we used it.

I do know there is a web interface for the powerwall where these settings may exist. There is no facility in the Tesla app to enable/disable a TOU feature (may vary if you also have solar). See next post.

But I just moved into a new area where the power company here does offer TOU rates $0.38 peak, $0.167 off peak) . But I also have a new solar order placed with Tesla (8.84kw), which includes moving my existing PW to my new home, plus one new additional referral powerwall. I hope the combination of TOU rates and 2 PWs will allow me to entirely avoid the on-peak rates. I think the way it will work is that the PWs will grid charge during off-peak hours, and during peak hours the house will run on solar+PWs. The solar array isn't large enough to run the house and charge the PWs for use during off-peak hours.

If you have solar, it is not going to "grid charge" at all, if you are in the US. which I believe you are (except for tesla triggered storm watch).
 

BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
I think the way it will work is that the PWs will grid charge during off-peak hours, and during peak hours the house will run on solar+PWs. The solar array isn't large enough to run the house and charge the PWs for use during off-peak hours.

If you have solar then the powerwalls won’t be allowed to charge from the grid at all (except in the case of stormwatch), so it will not work like that.

Instead, during off peak times it will charge the powerwalls from solar, even if that means running your house from the grid, then during peak times it will run the house from the powerwalls (and solar if it’s available).

It’s just semantics in the end though... either your powerwalls draw 20kW from your solar while your house draws 20kW from the grid, or your house draws 20kW from your solar while the powerwall draws 20kW from the grid. Either way you would have drawn 20kW from the grid. It just means that the powerwall can only charge while the sun is shining.
 

HankLloydRight

No Roads
Jan 18, 2014
12,893
10,891
Connecticut
Instead, during off peak times it will charge the powerwalls from solar

Well that sucks. The only time the PW can charge is during peak TOU hours (weekdays), so I'd have to draw all house power from the grid during those same peak hours.

How long will it take to charge two PWs from an 8.84kw solar system under normal conditions?

Charging the PWs via solar during peak hours means I have to pay during peak hours and then draw down the PW during off-peak hours. How does that make any sense?

It’s just semantics in the end though... either your powerwalls draw 20kW from your solar while your house draws 20kW from the grid, or your house draws 20kW from your solar while the powerwall draws 20kW from the grid.

The difference is that I should be able to grid charge the PW during OFF-PEAK hours. Why don't they allow grid-charging batteries?
 

getakey

Active Member
Jan 28, 2020
1,121
361
95762
The PW will charge during Partial Peak. You will power house from PWs durring Peak. You will pocket the difference between Partial Peak and Peak
 

BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
Well that sucks. The only time the PW can charge is during peak TOU hours (weekdays), so I'd have to draw all house power from the grid during those same peak hours.

Do you have no off peak hours during daylight at all?

How long will it take to charge two PWs from an 8.84kw solar system under normal conditions?

I mean that depends on what time of day it is and how much of a charge the powerwalls need. Your solar system will be producing much less power in the morning than mid afternoon, so charging will take longer in the morning.

However, each powerwall can hold about 13.5kWh of energy, so two would need 27kWh to charge from 0. Likely the powerwalls won’t be drained all the way down, though. If you keep your reserve at 50% then to go from 50% to 100% you would need about 13.5kWh. If your solar system was producing an average of, say 5kW of power from say mid morning to early afternoon then it would take just under 3 hours to charge the powerwalls.

Charging the PWs via solar during peak hours means I have to pay during peak hours and then draw down the PW during off-peak hours. How does that make any sense?

It doesn’t make any sense at all. If you really have no off peak times during daylight hours then you are probably better off just putting your powerwalls in backup only mode and allowing your solar system to power your house during the day.

The difference is that I should be able to grid charge the PW during OFF-PEAK hours. Why don't they allow grid-charging batteries?

It’s my understanding that no grid charging was a requirement to allow the powerwalls to qualify for the federal tax credit when installed with solar. However, unfortunately the side effect of that is that Tesla now forces any powerwall that’s installed with a solar system to only charge from solar, whether the tax credit is claimed on that powerwall or not. In other countries powerwalls are allowed to charge from the grid even when they are installed with solar.

If the solar tax credit is really removed in 2023 as is currently scheduled then it’s possible that tesla will remove this requirement, but that’s certainly not a guarantee. It’s also possible that the tax credit may be extended (in some form, at least) into 2023 and beyond.
 

HankLloydRight

No Roads
Jan 18, 2014
12,893
10,891
Connecticut
Then you would be charging from solar from Sunrisse to noon

Right, which isn't a lot of energy compared to the afternoon hours. So I might get a few hours of energy out of the PWs before going to the Peak hour rate, less whatever the solar is producing.

You'd think the power companies would welcome power-time-shifting to off-peak hours using the batteries. But they're enforcing just the opposite. :mad:

I guess I really won't know until the system is turned on.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,170
9,027
Riverside Co. CA
How long will it take to charge two PWs from an 8.84kw solar system under normal conditions?


Depends on your home loads, and production, of course. In my area, my 8.765 sized PV array is generating 30-33 kWh a day on a clear, sunny day. My daily run rate WAS about 27kWh a day, and I kept my reserve around 30% this time of year. I am using all this past tense because my daughter and her girlfriend moved back in with me while they are in between apartments.

They both have gaming PCs with dual monitors and are on them all the time when not working (they are both 27, and dont watch TV at all). Anyway, my energy usage has increased by like 40% because of their dual monitor + gaming PC setups.

I digress (lol). normally, my powerwalls are full by about 2pm but I am not on a time of use plan, I am on an old school plan which charges you for the total of what you use, with tiers for the more you use the more they charge you. So, I am incentivized to reduce total consumption, not WHEN I use power.

California has pretty good solar production in general (house angle, shading notwithstanding) so I would expect your similar sized system will generate similar production or less, for a similar time of year.

EDIT: These production numbers are "right now" as in mid October. My system in mid june generates around 50-53 kWh a day.
 
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BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
Partial Peak? The PWs will charge a little bit in the morning, but not enough to get through Peak hours, obviously.

Apparently in California they have three rates... Peak, Partial Peak, and Off Peak. I haven’t seen that rate structure used anywhere other than CA though.

Only on the weekends. Peak is 12noon-8PM M-F.

In that case the system would operate such that the powerwalls take as much of a charge as possible during sun-up to noon, running your house on the grid. Then at noon it would power your house with solar. Any excess solar would go to charge the powerwalls. (For example at noon your solar system might be generating 6.5kW but your house is only using 2.5kW, so it would still be able to send 4kW to the powerwalls to charge them). However, since it’s a peak time it will also draw from the powerwalls if the sun goes behind a cloud or after the sun sets.

It will continue drawing from the powerwalls until it is past the Peak rate time or until the powerwalls are drained to your reserve percentage. You may not be able to cover 100% of your peak use this way, especially on cloudy or rainy days, but you will still be able to cover a significant portion of it.
 
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