Charge PowerWall from grid?

Charge PowerWall from grid?

Does Tesla have any plans to allow the PW to be charged from the grid? Right now 100% of my solar production goes to offset my energy needs. My PWs will only charge if I select “back up only”.

If I could charge from the grid, I could use off peak energy to supply on peak demand.

smaches | August 18, 2019

To answer your second question first, some grid operators frown on this as it pulls from their bottom line. If you have TOU (time of use) billing, batteries can come in handy for powering your house during the peak billing hours just after sunset and usually until 9pm.
In my case, I do just that. I set the powerwalls to Self-Powered mode and the backup % to about 55 in the summer and 35 in the winter. I may set the unit to backup only or adjust the % to 20 above current charge level to force the controller to pull from the grid to charge the car on weekends when the TOU rate is lowest.
Now, the first question is a tough one as it *depends* on if you have solar or not. A customer with powerwalls only will have a grid tie and will use them for backup only (unless you force an outage by turning off the main breaker), but what's the purpose of that...maybe other than to test backup function.
And if your powerwalls only charge when in backup mode, I would think something was wrong - unless they were planned to be used in that function only. Good Luck.

smaches | August 18, 2019

One other thing to mention - STORM WATCH mode. If you have it available in your area and it is activated by a valid NOAA alert, it will fast charge your powerwalls using combination of panel and grid to ensure full charge in the event the storm does actually knock out your power. Pretty cool, eh?

zoomerdog | August 19, 2019

Smashes - thanks so much for your comments.
I have a 5kWh system which is not nearly enough to handle the energy needs of the house.

I like your idea of setting the backup % to 55. My peak usage is typically 7:00 to 8:00 pm.

I would love to have my 2 PWs offset the grid between 6:30 pm and 9:00 pm. However it seems to me that I have to manually make the change each day. In other words, I need to switch to “back up only” to charge the PW, and then switch to “self powered “ mode at 6:00 pm.

How are you managing your setting. Do you change them each day ?

smaches | August 19, 2019

ZD - Here's my setup: 4.8kW array feeding a 4.2kW ABB inverter coupled to two powerwalls to power a fairly modest 1500 sq ft stick and stucco tract home in San Diego about 20 miles from the coast. As I was looking for a system that could nearly zero me out each year with my electric usage, this combo package fit the bill.
Being retired also helps as I don't put a lot of mileage on the EV we have (Chevy Bolt), so after my first true-up last month, we owed the local grid $8.00 for the year, minus the mandatory monthly meter fee.
So, that being said, I hardly ever have to switch between modes to charge, as my generation exceeds my consumption most days of the year. Sounds from your comment that you consume all you generate and possibly also pull from the grid during each daily cycle, which would explain the powerwalls charging when in Backup only mode since there's no daily excess from your array.
The solution? Probably expensive...

gregbrew | August 19, 2019

In the US, public electrical utilities generally don't allow charging PWs from the grid, except during Stormwatch emergencies. I remember when it *was* possible, in the late '90s and early '00s, then the utilities woke up to the fact that someone on a TOU and time-shifting their usage was eating their lunch. In those days, it was possible to pay off your battery pack in less than three years using this method.

If I'm not mistaken, Australian electrical utilities still allow time-shifting with batteries, but for how much longer?

zoomerdog | August 19, 2019

I just spoke w Tesla support today. Apparently Tesla has just changed the algorithm. It appears to be a work in progress.

I got the PWs last week so it is a bit early to see how the new algorithm works. I’ve got it set to customized/advanced /cost savings. My biggest power usage is 6 to 9 pm and I have the peak period starting at 6 pm (although Peak runs from 10 am to 9 pm). I just want it to offset demand after the sun goes down.

So far the algorithm has discharged slightly during the day, but has also recharged the PWs so that in they are entering the Peak 6 pm period with +95% capacity.

I’ll post what happens over next couple of days

zoomerdog | September 16, 2019

Just following up on my earlier post. So far so good, and very pleased.
We had a hurricane come thru here 10 days ago, the lights flickered, and the battery backup started -- just as it is supposed to,
So far the 2 PWs are satisfying 100% of my energy needs between 6:00 pm and 9:00 pm.

chobao | December 6, 2019

I'm thinking about getting PW to shift the time of use just like what you did. Does PW charge from both solar and grid during off-peak time?

gregbrew | December 7, 2019

No. In the USA, the majority of utilities (check with yours) do NOT allow PWs to charge from the grid, except in a an impending power emergency via Stormwatch. They are set up to charge solely from the PV array.

Wilkes.r | December 26, 2019

That really doesn't make sense... I thought folks were able to buy the Powerwall to be used solely as 'backup' power? Even if utility companies 'didn't allow' the PW to charge at the specific times, I'm not sure how it could prevent it. I could relatively easily charge a 200KW battery pack at night using Utilities and then narrow my utility band width.... I can control all that after the 'meter' - Many folks get EV credit from utilities; same concept.

bp | December 27, 2019

Also - if you take the 30% US federal tax credit for the PowerWall purchase, they are supposed to be charged only by solar (except for emergencies) during the first 5 years.

Plus, Tesla's warranty is different if you charge from the grid vs. charging from solar.

PapaSmurf | December 27, 2019

"they are supposed to be charged only by solar (except for emergencies) during the first 5 years"

What happens at the end of 5 years?
Will Tesla release more functionality and allow us to specify recharge the PW from the grid?

gregbrew | December 27, 2019

Wilkes.r, Yes, you could do it, but you would be doing so without a city building permit. Without utility approval (they won't give it to you), you can't get a building permit. It's part of the process. You'd have to "do it yourself", because any licensed and bonded electrician wouldn't touch such a project, because they could lose their license and insurance, if caught.

It has nothing to do with safety or infrastructure...the utility simply doesn't want you to reduce their profits by time-shifting with storage. *They* can do it (as with pumped hydro), but you can't. Utilities have strong lobbying divisions...