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No more outage anxiety

ceekz

Member
May 14, 2018
465
477
Sacramento, CA
So, the only way to tap into solar power during an outage is to utilize battery storage... it made me a little nuts when we had our solar installed a few years back and I learned that power to the meter from the grid is required to use solar power. Last year, we made the decision to increase the number of panels on our roof to support battery storage, and Tesla Solar completed the install yesterday.

Suck it, PG&E! OK, I admit we have municipal power and not PG&E, but it felt good to say that anyway. Ironically, it is cheaper for me to pay SMUD's EV off-peak rates to charge the Tesla between 12-6 AM and use the batteries to power the house during the peak usage hours (5-8 PM), so going full solar for the Model 3 is not likely to happen.

The Tesla app appears to make it easy to prioritize the battery charging (to specify if it charges from the grid or from solar), and also how it discharges (to charge the car or power the house).

I'm interested in hearing from other Powerwall owners who use the battery to charge their cars, particularly during an outage.
Powerwall.jpg
 

devilmountain

Member
Jan 31, 2018
294
245
Walnut Creek
So, the only way to tap into solar power during an outage is to utilize battery storage... it made me a little nuts when we had our solar installed a few years back and I learned that power to the meter from the grid is required to use solar power. Last year, we made the decision to increase the number of panels on our roof to support battery storage, and Tesla Solar completed the install yesterday.

Suck it, PG&E! OK, I admit we have municipal power and not PG&E, but it felt good to say that anyway. Ironically, it is cheaper for me to pay SMUD's EV off-peak rates to charge the Tesla between 12-6 AM and use the batteries to power the house during the peak usage hours (5-8 PM), so going full solar for the Model 3 is not likely to happen.

The Tesla app appears to make it easy to prioritize the battery charging (to specify if it charges from the grid or from solar), and also how it discharges (to charge the car or power the house).

I'm interested in hearing from other Powerwall owners who use the battery to charge their cars, particularly during an outage.
View attachment 467482
Was it a pain to have Tesla add additional panels to the existing system? I had my solar system sized for 1 model 3, not two of them. I now own two model 3's and would prefer to have my solar system resized. I looked at adding a powerwall but Tesla stated I needed to spend an additional 15k to upgrade the service line from the street. I never understood why I need that replaced, and nobody adequately explained it to me. My house was built in 79.
 

MorrisonHiker

Well-Known Member
Mar 8, 2015
10,233
9,953
Colorado
We just had another Powerwall added at the end of September. Thanks to the Powerwalls and our solar system, we can theoretically go indefinitely off the grid if there is an outage since there are 300+ sunny days a year in our part of Colorado. We had a 45 hour outage last year and the Powerwalls kept things up for the first 24 hours. We did have an issue on the second day when the Powerwalls set too high of a frequency and caused the solar to turn off an on all day long. Tesla did some firmware updates since then to address the issue. We did a 7 hour outage test on Wednesday and had no problems. We'll be doing a multi-day off-grid test next. We have no problems charging our Teslas from the Powerwalls other than the fact that the total Powerwall kWh capacity is much less than the battery capacity of our Teslas. We did have one multi-hour outage where the Powerwalls were drained overnight due to multiple cars that started charging during the outage and we didn't know there was an outage since we were asleep. We've tweeted Elon and asked for better communication between the Powerwalls and Tesla vehicles. He replied that better communication is coming in a future update.

@AdamVIP , Powerwalls have about 13.3 kWh of storage each. If you have at least two Powerwalls, they can backup the entire house. Depending on your household load, they could last you an hour to several days. When combined with solar, they automatically recharge and with sufficient sunlight you can power your house (and cars) off the grid indefinitely.

BTW, @ceekz , there is a Tesla Energy forum on this site with lots of existing threads discussing Powerwalls and solar.
 

miimura

Well-Known Member
Aug 21, 2013
6,540
6,351
Los Altos, CA
The Tesla app appears to make it easy to prioritize the battery charging (to specify if it charges from the grid or from solar), and also how it discharges (to charge the car or power the house).

I'm interested in hearing from other Powerwall owners who use the battery to charge their cars, particularly during an outage.
You will find that Powerwalls installed in the USA and paired with solar can only charge from solar except when Storm Watch is active. This makes the Powerwalls ITC compliant so that you can take a tax credit of 30% of your net cost of the Powerwalls and solar. If you set up Time Based Control in the app, you can tell it when your expensive power is and it will power your house from the batteries during that period and let your solar go to the grid to earn you maximum NEM credits.

My car charging circuits are not backed up. So, during an outage I would only be able to plug my cars into the 120V outlets in my garage that are backed up. However, I have a small solar system so I'm unlikely to have energy to spare for the cars during an outage.
 

gpez

Member
Apr 25, 2019
735
602
USA
You will find that Powerwalls installed in the USA and paired with solar can only charge from solar except when Storm Watch is active. This makes the Powerwalls ITC compliant so that you can take a tax credit of 30% of your net cost of the Powerwalls and solar. If you set up Time Based Control in the app, you can tell it when your expensive power is and it will power your house from the batteries during that period and let your solar go to the grid to earn you maximum NEM credits.

My car charging circuits are not backed up. So, during an outage I would only be able to plug my cars into the 120V outlets in my garage that are backed up. However, I have a small solar system so I'm unlikely to have energy to spare for the cars during an outage.

Same here - my car charging circuit is not backed up but I could use the 120v outlets in an outage. This is entirely by design as the DC-AC-DC conversion losses stack up quick so I'd likely only charge the car if the solar production is higher than the house consumption AND the Powerwall is full.

Welcome to the Powerwall club, @ceekz! Having no outage anxiety is quite freeing :)
 
Jun 22, 2017
527
338
Bay Area, California
Two EV charging stations in the house, one car. One Clipper Creek J1772 32A charge station, from previous EV; and one 100A Tesla Wall Connector. The J1772 is hooked up to the battery backup load center, and is backed up. The Tesla one is not backed up and is powered directly by the grid/service panel... this way, if power went out at night, the car batteries won't deplete the PWs.
 

GenSao

Member
Aug 3, 2017
565
966
Pleasant Hill, CA
I'm interested in hearing from other Powerwall owners who use the battery to charge their cars, particularly during an outage.
View attachment 467482

@ceekz Congratulations on your Powerwalls and more solar! Being (more) energy independent is awesome.

Regarding car charging, we charge our Tesla and PHEV overnight using grid power as it is most economical to do so. Our 40 A NEMA 6-50 EV plug is backed up. I am working on installing more solar and a 60 A Tesla wall connector (outside of the backup panel).

As it is just software, I hope Tesla in the future will integrate Powerwalls and charging Tesla cars. The cars could be specifically set to charge by solar power only (after Powerwalls are charged to a set level). In the event of a power outage, charging can stopped or limited (depending on battery states, time of day, settings, etc.).
 

ceekz

Member
May 14, 2018
465
477
Sacramento, CA
@GenSao, I agree. I'd like to see more functionality added to the app. I did not know until after the install that the PWs couldn't be charged from the grid. Right now it is app rodeo (with both me and my husband making changes) to figure out how to optimize the charging of the PW with solar vs powering the house especially with peak, off-peak, and EV charging rates! I expect it will be easier after inspection and the additional panels are powered on and our ability to generate power increases.

It should have been easy to add the battery storage to the existing solar set up, except we needed more panels to support the house and charge the batteries. The original inverter and electrical panel were too small to handle the bigger load. So, a full upgrade on the panel was required, and a new inverter and additional solar was added. I don't know that we'll live in the house long enough to recuperate the cost, but the trade off for clean energy and grid independence is priceless.
 
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