Exporing Powerwall for loadshifting in TX

[Electroman]

I am in a TXU plan that gives me free power at night from 8 pm to 6 am, with a 5c increased rate during the day time than the cheapest option. Basically the cheapest option is around 10c/kWh all time of the day, and the free nights plan is 15c / kWh from 6 am to 8 pm and 0c rest of the time.

Given the above I was thinking I can install a PW or two, charge during the night and use that during the day and reduce my TXU bill to the bare minimum. I checked with TXU and they are okay with this.

Here are my questions that I can't seem to good answers on the Tesla website:

• Is this a good use case for getting a PW? or am I overlooking something obvious.

• What it the battery capacity of each PW? Why is that not mentioned at all on the website?

• Is the PW designed and can withstand this usecase of charge & discharge everyday? or is it only for occasional outage and backups?

• I called Tesla customer support and the prices (only PW and no Solar) I was given differs quite a bit from Tesla webpage:

Tesla Website lists 2 PW as $13,000 + $1,100
Customer rep sent me an email quoting: "The cost of PW without solar is as follows: 1 PW cost is $10,500. 2 PW cost is $17,000 3 PW cost is $24,500"
​

• What additional hidden costs should I be aware of?

I would love to meet up with a home owner here in the north DFW area that has installed PW and would be kind enough for me take a look and have a chat.

 

[getakey]

PW is designed to charge/Discharge everyday. You can set up the schedule in the App. I only know how that works if you have solar, but I know load shifting is a valid application of PW without solar
Capacity of each PW is 13.3kWh

I'm in CA and I just paid 33K for installation of 3. That included replacing my main panel and adding a new subpanel. We have a rebate program in CA that ran out for 1 or 2 PW installs, but still available for 3. So here if you buy 2, you might as well buy 3. My net price will be $15K

 

[miimura]

Each Powerwall has a usable capacity of 13.5kWh. If you are not going to get solar and the prices are really what you say, I would not do it. You would be better off paying 10c/kWh. Here's my logic. $0.10/kWh * 13.5kWh = $1.35 per Powerwall per day savings. 3 Powerwalls cost $24,500 so the payback is $24,500 / ($1.35 * 3 * 365) = 16.5 years. The warranty is only 10 years. Also, if you use more than 40kWh in any given daytime period, you will also owe $0.15/kWh for any excess. Your utility may also have minimum charges that you wouldn't see with normal usage.

 

[Electroman]

Here's my logic. $0.10/kWh * 13.5kWh = $1.35 per Powerwall per day savings. 3 Powerwalls cost $24,500 so the payback is $24,500 / ($1.35 * 3 * 365) = 16.5 years. The warranty is only 10 years.

Thanks for making the ROI calculation simple.

Why does Tesla.com site tell me $20,600 for 3 PW, whereas Tesla rep is quoting me $24K ?

 

[jjrandorin]

I am in a TXU plan that gives me free power at night from 8 pm to 6 am, with a 5c increased rate during the day time than the cheapest option. Basically the cheapest option is around 10c/kWh all time of the day, and the free nights plan is 15c / kWh from 6 am to 8 pm and 0c rest of the time.

Given the above I was thinking I can install a PW or two, charge during the night and use that during the day and reduce my TXU bill to the bare minimum. I checked with TXU and they are okay with this.

Here are my questions that I can't seem to good answers on the Tesla website:

• Is this a good use case for getting a PW? or am I overlooking something obvious.

• What it the battery capacity of each PW? Why is that not mentioned at all on the website?

• Is the PW designed and can withstand this usecase of charge & discharge everyday? or is it only for occasional outage and backups?

• I called Tesla customer support and the prices (only PW and no Solar) I was given differs quite a bit from Tesla webpage:

Tesla Website lists 2 PW as $13,000 + $1,100
Customer rep sent me an email quoting: "The cost of PW without solar is as follows: 1 PW cost is $10,500. 2 PW cost is $17,000 3 PW cost is $24,500"
​

• What additional hidden costs should I be aware of?

I would love to meet up with a home owner here in the north DFW area that has installed PW and would be kind enough for me take a look and have a chat.

The cost of the powerwall on the tesla website does not include installation. Powerwalls are:

6500 each powerwall hardware
1100 Gateway (need 1)
Installation costs for "standard" installation are 3000 for 1 powerwall, 2500 for 2 powerwalls (yes its cheaper install price to install 2 than install 1), 4000 3 powerwalls.
Taxes

So 1 powerwall is 6500 + 1100+ 3000 + taxes. (the same as they quoted you)
2 powerwalls is 6500 + 6500+ 1100 + 2500 + taxes (same as they quoted you)
3 powerwalls would be 6500 + 6500 + 6500 + 1100 + 4000 + taxes

Powerwall is designed for charge and discharge, thats no issue. If you dont have solar, however, you will not be able to get any tax credits on the powerwall. Your power is so cheap, if you buy, say 3 powerwalls, without solar, your looking at 24,500. How much "free" power would you have to defer to break even on that?

With the cost of your power, if being backed up from a power outage isnt a concern, I dont know how powerwalls make sense just from a pure dollars and cents point of view.

 

[garrett5688]

Like stated above, the ROI in Texas is long. I understand going solar for other reasons. But Texas electricity is some of the cheapest in the country. Unless you are easily able to shift your usage into the free period, my guess is you could find a cheaper 24/7 rate and come out ahead. I think I pay .08-.09/kWh no matter time of day or usage amount.

if you have a smart meter, you can download your usage history and chart it to see how it compares to the TOU plans. It didn’t makes sense for me.

 

[Electroman]

Thanks everyone. All these insight really helps.

 

[Electroman]

Like stated above, the ROI in Texas is long. I understand going solar for other reasons. But Texas electricity is some of the cheapest in the country. Unless you are easily able to shift your usage into the free period, my guess is you could find a cheaper 24/7 rate and come out ahead. I think I pay .08-.09/kWh no matter time of day or usage amount.

if you have a smart meter, you can download your usage history and chart it to see how it compares to the TOU plans. It didn’t makes sense for me.

I did a calculation comparing two 12 month period - one with 9c plan and the other with free-night 15c plan - what I saw was that, with my Tesla charging at night, I saved around 15% in the free nights plan over the cheapest 9c plan. I may add a Model Y and kick out the remaining gas SUV, and that will save another 10% I would think.

 

[bob_p]

When we were planning our solar panel/PowerWall system, we looked at the possibility of a PowerWall-only configuration, and decided against that option (in TX).

The federal tax credit (26% this year, 30% last year) can lower the cost of the system when PowerWalls are installed with solar panels. Without solar panels, you can't use the tax credit. And even if you have solar panels , if you take the tax credit, you are prohibited from charging the PowerWalls from the grid (except for emergencies, like hurricanes), at least for the first 5 years.

While a utility today may allow you to use a PowerWall to charge overnight for free and use power during the day, there's no guarantee that will be allowed in the long term. The "free nights" plans are mostly a gimmick. The utilities make an estimate of how much power they believe you'll use during the day vs. the free nights periods, and then increase rates for the day to ensure they generate a comparable amount of income under a free nights plan vs. a normal plan. And using a PowerWall to game the system could mean they'll lose money on that account - something they'll unlikely do in the long run.

The PowerWall warranty is for 10 years, unlimited charging cycles UNLESS the PowerWall is being charged by the grid, when the warranty is capped by charging cycles. If you regularly run the PowerWalls from 0-100% each day, the warranty likely won't last the full 10 years.

WIth the relatively low electric rates in TX, it may be difficult to justify paying full price for PowerWalls and assume you'll always be able to charge at night for free and run off that power during the day.

Instead, what we did was install solar panels and 4 PowerWalls, and expect we'll be able to significantly reduce our electric bill while also having enough power to operate off grid for days after a hurricane.

 

[garrett5688]

4 power walls!

 

[jjrandorin]

4 power walls!

Everythings bigger in Texas, right?

 

[charlesj]

...

I'm in CA and I just paid 33K for installation of 3. That included replacing my main panel and adding a new subpanel. We have a rebate program in CA that ran out for 1 or 2 PW installs, but still available for 3. So here if you buy 2, you might as well buy 3. My net price will be $15K

How much is the rebate itself for 3 PW. Will call my coordinator in the morning and see. Wonder if I could place 3 in the garage.
I am presuming your permit was approved last year?

 

[getakey]

Rebate is about 8K
yes permit last year

 

[Electroman]

And even if you have solar panels , if you take the tax credit, you are prohibited from charging the PowerWalls from the grid

What is taking tax credit to do with charging the PW from the grid? Why are these two related at all?

 

[reddy]

What is taking tax credit to do with charging the PW from the grid? Why are these two related at all?

The tax credit is for the solar energy tax credit, not for arbitrage on time of use. Not having solar , you don't meet the criteria.

I have 4 Powerwalls, in Texas. Connected to solar. I'm not in the ERCOT area that has net metering, which gave me the financial use case.

Re: not charging from the grid, there is not an absolute prohibition. Powerwalls have an emergency mode that is triggered if there are weather conditions forecast that may cause power outages. In that case, your Powerwalls will begin charging from the grid before the weather arrives. I've had that event happen twice. It can be toggled off if you don't want it.

Also, FWIW, I had a 30 hour grid outage , a matter of weeks after the Powerwalls were installed, due to a massive windstorm. I was the only home in our subdivision with power all that time.

Which company is installing your Powerwalls ?

 

[bob_p]

When our system was installed, we looked into fixed rate, buyback and free nights plans for use with our solar panels/PowerWalls. And before we signed the contract for the system, we also looked into using PowerWalls with free nights plans (charging at night and using the PowerWalls during the day).

Because a PowerWall-only system doesn't get the federal solar tax credit (30% last year, 26% this year), coupled with the likelihood utilities will eventually exclude battery storage from free nights plans, we decided against purchasing only PowerWalls. Plus, a PowerWall-only system would achieve our goal of being able to operate off grid for multiple days after a hurricane.

With our solar/PWs, we're estimating we'll generate about 50% of the electricity we use (hopefully better). When selecting the plan we would use first with our new system, we evaluated fixed price ($.091/KWh), free nights ($.191/KWh during the day; free nights) and buyback ($.149/KWh), we decided to go with the fixed price plan for 6 months, and then using actual meter data, re-evaluate our different options mid-year.

Getting back to the OP's interest in PowerWall-only, while this is technically possible, there's no guarantee utilities will always allow battery storage under the free nights plans, the price of PowerWalls without solar panels is higher (because it doesn't get the credit), and the PowerWall warranty could be reduced by powering from the grid.

Instead, would recommend looking at a combined solar/PowerWall system - and instead of going for 100% of electric usage, shoot for a lower number (we picked 50% because we believe we can cut our energy usage by 50% for extended off grid).

 

[LCR1]

Each Powerwall has a usable capacity of 13.5kWh. If you are not going to get solar and the prices are really what you say, I would not do it. You would be better off paying 10c/kWh. Here's my logic. $0.10/kWh * 13.5kWh = $1.35 per Powerwall per day savings. 3 Powerwalls cost $24,500 so the payback is $24,500 / ($1.35 * 3 * 365) = 16.5 years. The warranty is only 10 years. Also, if you use more than 40kWh in any given daytime period, you will also owe $0.15/kWh for any excess. Your utility may also have minimum charges that you wouldn't see with normal usage.

This, the only other upside is you have backup when the power actually does go out. Can't predict the price of electricity but they say it's only going to go up. I'm still paying around 7-8 cents after tax in Houston when everyone else complains about 12-14

 

[getakey]

you guys are lucky on rates. I'm on PG&E. My summer peak rate is .52/kWh. Winter peak is .32/kWh
However, my solar ROI is 4 years

 

[charlesj]

Rebate is about 8K
yes permit last year

Did you have to install another meter as I just read that 3 PW is considered large and utility co. wants an extra meter?
Also, who applied for that rebate, you or Tesla?
I have to pull the trigger today or by Tuesday to go with 2 or 3.
Thanks

 

[jjrandorin]

Did you have to install another meter as I just read that 3 PW is considered large and utility co. wants an extra meter?
Also, who applied for that rebate, you or Tesla?
I have to pull the trigger today or by Tuesday to go with 2 or 3.
Thanks

In order for him to get that rebate, he is likely going with a third party installer as tesla is already over subscribed for SGIP, is my understanding. you need to ask your installer company (if its not tesla) if they have availability for SGIP. The installer applies on your behalf, as the developer.

See his install cost of 3 powerwalls of 33k. Teslas install cost for 3 powerwalls is 24.5k Hes getting 8k in SGIP for large install. That beings the install price for 3 down to 25k, which is the same as tesla is charging without access to SGIP for 3 powerwalls.

The tax credit is the same for both as that is something an individual tax payer puts on their taxes.

In effect, the installer that @getakey has is charging enough for the 3 powerwall install that the total price comes to the same as teslas without the SGIP, which is consistent with what I found when I was getting quotes. There are other reasons to go with a third party that are completely valid, but pricing does not normally end up cheaper through them than Tesla direct.