NorCal PG&E blackouts

[bayareaever]

Interesting thread. I'm also in the Bay Area and am considering a new PW install to protect against blackouts (I was luckily spared in the last one), and for rate arbitrage to pair with existing solar system.

By far our biggest load (besides EV charger) is an on demand electric water heater, which is also arguably the most important during a prolonged outage.

It is rated at 28 kw peak but generally uses about 15 kw for showering and 25 kw for filling the bathtub (according to PG&E Smart Meter). It uses 3 40 amp breakers on the main panel. I'm fine if we can't use the bathtub during an outage but if the shower trips the PW breaker during an outage then I'd be frustrated to say the least. The water heater manufacturer rep I spoke with isn't sure how a battery would handle the load because it pulses rather than drawing continuously.

Tesla certified installer claims PW could never back up the water heater, but I think they said that because they have no interest in installing more than two. Certainly, some number of Powerwalls could handle it?!

Tesla has given me a quote on a 3 PW install for whole house backup (as per my request) but I'm weary that they haven't really looked at the load and 3 actually wouldn't be enough. Anybody have insight into proper PW number to properly power this load?

 

[power.saver]

Each Powerewall is rated 5kW, so if you want 25kW you would need 5 of them. And that's assuming no other loads.

You won't be able to heat up your water with Powerwalls and shouldn't try to, because if they overload you will have no power.

 

[KJD]

Interesting thread. I'm also in the Bay Area and am considering a new PW install to protect against blackouts (I was luckily spared in the last one), and for rate arbitrage to pair with existing solar system.

By far our biggest load (besides EV charger) is an on demand electric water heater, which is also arguably the most important during a prolonged outage.

It is rated at 28 kw peak but generally uses about 15 kw for showering and 25 kw for filling the bathtub (according to PG&E Smart Meter). It uses 3 40 amp breakers on the main panel.

The water heater drawing 25 kW is going to be a bit of problem for the power wall that is rated at 5 kW continuous.
Tesla Powerwall

I guess that you could install 5 or 6 power walls and maybe it would work, but the cost seems prohibitive. Why not get a more efficient water heater, like this one that uses a heat pump.
Stiebel Eltron 58 Gal. Heat Pump Hybrid Electric Water Heater-Accelera 220 E - The Home Depot

The cost of the new water heater would be less than one power wall. This model installs on one 240 volt 15 amp breaker.

 

[nwdiver]

By far our biggest load (besides EV charger) is an on demand electric water heater, which is also arguably the most important during a prolonged outage.

Have you seen this thread?

Tankless water heaters are terrible....

Getting a heat pump water heater (if you have room for a tank) is by far the most cost effective solution. My HPWH is one the main reasons I've been able to largely go off grid. The compressor only uses ~500w and I just heat it during the day when the PV is producing.

 

[bayareaever]

I don’t have much extra room for a tank water heater and the basement is already cold so I don’t really want to make it colder with a heat pump. It would also share the space with the furnace so probably not ideal in terms of efficient house heating.

I’m hoping 4 PWs can handle the on-demand heater. 20 kw continuous output/ 28 kw peak output is in line with what the water heater uses (typically 15 kw as mentioned above).

But, admittedly, it is pushing the limits of 4, and 5 PWs is probably too expensive/not feasible.

 

[nwdiver]

I don’t have much extra room for a tank water heater and the basement is already cold so I don’t really want to make it colder with a heat pump.

You can duct a Rheem HPWH so it will discharge outside.

 

[EV-by-the-Sea]

Post the photo here... we'll get back to you sooner than they will

Alright -- I'll give it a shot as I haven't heard back from support yet. It's a Bryant Plus 80 furnace. I'm attaching a photo that includes the most detail I was able to find inside the furnace. I guess the questions are -- plausible that it drew too much current for the powerwall? And, would this work with a soft start kit?

 

[power.saver]

It doesn't state LRA, but being only 115V and 5.9A run, it should not have tripped the PW.

 

[gpez]

For me, my power went out on Wednesday at 11:58 pm. I knew I was in an affected area per PG&E's maps and address lookup tool. Comcast internet access went out at 12:45 am. I confirmed by visiting my cable modem's status page (http://192.168.100.1/).

At that point, I just turned off power to the UPSes running my cable modem and wireless access point. I checked the Xfinity app and it listed an unplanned outage for me also affecting 2500+ customers. It was still like that when I left for work in the morning (no power and no Comrap).

Once the power went out, I went to work on unwinding and untangling extension cords and getting my 1000 watt pure sine wave inverter hooked up to my Bolt (had tested it before and it could start and run my fridge). I kept that going all night until I went to work and had to leave. I powered my fridge, laptop, some lights and my security camera NVR system. When I was awake, I had to tether my laptop to a cell phone to surf the net.

For the Bolt, the car must be left in ready mode otherwise the 12 volt will go flat. To workaround a stupid 1 hour timeout where the car shuts itself off if left in park for an hour, I had keep it neutral and exit from the passenger side. Basically, enter from passenger side. Use a rod or stick to push the brake pedal and shift to neutral. Exit from passenger side. That's easier the than doing it from the driver's side and having to climb over to exit from the passenger side.

My power came back around 3 pm on Thursday, which is much earlier than I expected. I expected to be w/o power until at least sometime Friday.

Fortunately, my work (w/free L2 charging) wasn't affected and areas just a few miles away from home also weren't affected. There are 2 paid DC FCs within 7 miles of home (if I needed to use them) and I'm pretty sure they weren't in affected areas.

@cwerdna I have a Chevy Volt and have a similar setup that I have (fortunately) not had to use yet to augment my Powerwall in the case of a prolonged or winter (read: no solar) outage. I have a few questions for you!

Have you seen the "rubber band trick"? At least on the Volt supposedly simply keeping the shifter button depressed with something like a rubber band prevents the car from turning off and avoids the drained 12v problem you mention.

Do you have a permanent install like the evextend kit for your Bolt or are you using something simple like alligator clips?

Really curious about the efficiency of the traction DC -> 12v DC -> AC inverter. Do you know about how many kWh you consumed at the AC end and what the total consumed kWh on your traction battery was?

Finally, how does the Bolt measure that load? I imagine to it the inverter can't be accounted for from another system so I'm guessing it shows up under "other"?

 

[Dan123]

Interesting thread. I'm also in the Bay Area and am considering a new PW install to protect against blackouts (I was luckily spared in the last one), and for rate arbitrage to pair with existing solar system.

By far our biggest load (besides EV charger) is an on demand electric water heater, which is also arguably the most important during a prolonged outage.

It is rated at 28 kw peak but generally uses about 15 kw for showering and 25 kw for filling the bathtub (according to PG&E Smart Meter). It uses 3 40 amp breakers on the main panel. I'm fine if we can't use the bathtub during an outage but if the shower trips the PW breaker during an outage then I'd be frustrated to say the least. The water heater manufacturer rep I spoke with isn't sure how a battery would handle the load because it pulses rather than drawing continuously.

Tesla certified installer claims PW could never back up the water heater, but I think they said that because they have no interest in installing more than two. Certainly, some number of Powerwalls could handle it?!

Tesla has given me a quote on a 3 PW install for whole house backup (as per my request) but I'm weary that they haven't really looked at the load and 3 actually wouldn't be enough. Anybody have insight into proper PW number to properly power this load?

I think 6 PWs would do it.

Frankly, I think rather than increasing the number of Powerwalls, it would be cheaper for you to install a separate dedicated water heater for 1 shower. it's power draw could be satisfied by 2 powerwalls, and the cost will be probably less than $1000.

 

[cwerdna]

@cwerdna I have a Chevy Volt and have a similar setup that I have (fortunately) not had to use yet to augment my Powerwall in the case of a prolonged or winter (read: no solar) outage. I have a few questions for you!

Have you seen the "rubber band trick"? At least on the Volt supposedly simply keeping the shifter button depressed with something like a rubber band prevents the car from turning off and avoids the drained 12v problem you mention.

Do you have a permanent install like the evextend kit for your Bolt or are you using something simple like alligator clips?

Really curious about the efficiency of the traction DC -> 12v DC -> AC inverter. Do you know about how many kWh you consumed at the AC end and what the total consumed kWh on your traction battery was?

Finally, how does the Bolt measure that load? I imagine to it the inverter can't be accounted for from another system so I'm guessing it shows up under "other"?

Yes. I've heard about the rubber band trick. IIRC, it doesn't work on the Bolt. I will need to double check (Bolt forums) when I get a chance.

Sorry, my other answers won't be too helpful.

No on the permanent install, yet. Am using just large alligator clips. There's at least one guy at Chevy Bolt EV Forum who does have a more permanent setup.

As for consumption, sorry, no idea on the AC end and I didn't bother tracking it on the car end.

Sorry, I didn't even bother looking at how it categorized the energy use. The 3 categories on the Bolt's display are "driving and accessories", "climate settings" and "battery conditioning". There's no "other". From "Camping Mode" Test Results, it sounds like it categorizes it as "driving and accessories". I think I confirmed this before when I tested my setup months back. It was most definitely NOT battery conditioning.

I barely got any sleep during that outage because I was so concerned that the car might auto turn off (so I'd wake to check it every few hours) and I needed to be at work for a meeting at a certain time in the morning. I already had to spend extra time leaving to disconnect my setup, manually open and close my garage door, etc.. as the power was out when I left for work.

IIRC, a rough guesstimate on that forums about efficiency of all those conversions + the Bolt's (in READY mode) draw was that probably there's ~50% loss in total.

If I didn't have the lack of sleep issue and didn't need to be on time for a meeting, I could've taken down info.

 

[bmah]

For us, we were able to exist quite comfortably with our 5.8kW solar array and 3 Powerwalls during our 36 hours of PSPS. By not charging cars and being careful about appliance usage we could probably have gone for days this way, as long as we had sunny weather and fairly mild temperatures. I am currently working with Tesla Energy support to resolve a couple issues with solar curtailment, but overall I'm pretty pleased with how this worked out.

"Powerwall Moment": We got power back mid-day on Friday. That afternoon, my son came home from school, and he'd been home for at least 20 minutes when he bothered to ask, "Hey Dad, did our power come back on yet?"

Bruce.

 

[miimura]

"Powerwall Moment": We got power back mid-day on Friday. That afternoon, my son came home from school, and he'd been home for at least 20 minutes when he bothered to ask, "Hey Dad, did our power come back on yet?"

Bruce.

Yeah, when the house has been running on the Powerwalls the only way I can tell whether the utility power is back on or not is to check the Tesla app or go look at the lights on one of the EVSEs that is not backed up. Inside the house, I really can't tell.

 

[bayareaever]

I think 6 PWs would do it.

Frankly, I think rather than increasing the number of Powerwalls, it would be cheaper for you to install a separate dedicated water heater for 1 shower. it's power draw could be satisfied by 2 powerwalls, and the cost will be probably less than $1000.

Tesla installer looked at my detailed pge usage and determined that 3 PWs would suffice. I still think 4 is a safer bet but I’m quite sure 6 is overkill. A smaller supplemental water heater is a possibility but the bigger one I have now automatically modulates the power draw based on water flow, etc so I’m not sure the smaller one would achieve anything.

 

[gpez]

Yes. I've heard about the rubber band trick. IIRC, it doesn't work on the Bolt. I will need to double check (Bolt forums) when I get a chance.

Sorry, my other answers won't be too helpful.

No on the permanent install, yet. Am using just large alligator clips. There's at least one guy at Chevy Bolt EV Forum who does have a more permanent setup.

As for consumption, sorry, no idea on the AC end and I didn't bother tracking it on the car end.

Sorry, I didn't even bother looking at how it categorized the energy use. The 3 categories on the Bolt's display are "driving and accessories", "climate settings" and "battery conditioning". There's no "other". From "Camping Mode" Test Results, it sounds like it categorizes it as "driving and accessories". I think I confirmed this before when I tested my setup months back. It was most definitely NOT battery conditioning.

I barely got any sleep during that outage because I was so concerned that the car might auto turn off (so I'd wake to check it every few hours) and I needed to be at work for a meeting at a certain time in the morning. I already had to spend extra time leaving to disconnect my setup, manually open and close my garage door, etc.. as the power was out when I left for work.

IIRC, a rough guesstimate on that forums about efficiency of all those conversions + the Bolt's (in READY mode) draw was that probably there's ~50% loss in total.

If I didn't have the lack of sleep issue and didn't need to be on time for a meeting, I could've taken down info.

No problem at all, was just very curious as I have (fortunately) not yet had to have put my setup to the test and am just gathering as much info as I can. On the Volt I have "Driving", "Climate", and "Other". Hopefully you learned a bit from this experience to help the next time it happens!

 

[JPP]

Yeah, when the house has been running on the Powerwalls the only way I can tell whether the utility power is back on or not is to check the Tesla app or go look at the lights on one of the EVSEs that is not backed up. Inside the house, I really can't tell.

...but if your internet/ISP is down, even if your home network is up, will the Tesla app 'see' the gateway/Powerwall to let you know its status?

 

[bmah]

...but if your internet/ISP is down, even if your home network is up, will the Tesla app 'see' the gateway/Powerwall to let you know its status?

Good point. The Tesla app relies on back-end servers at Tesla for Powerwall interactions, just like for the cars.

However unlike the cars, you can actually query data from the Powerwall gateway on your local network (not with the app but with custom code).

Bruce.

 

[JPP]

Good point. The Tesla app relies on back-end servers at Tesla for Powerwall interactions, just like for the cars.

However unlike the cars, you can actually query data from the Powerwall gateway on your local network (not with the app but with custom code).

Bruce.

...'custom code'....great for the 'ordinary' homeowner...

When my local neighborhood loses power, in maybe 10-30 minutes, Comcast goes down, likely as some kind of backup battery on a coax amp or switch runs down. Makes me sort of wonder about going with a satellite ISP as redundancy.

 

[ohmman]

...'custom code'....great for the 'ordinary' homeowner...

While I don't think it's in the reach of 'ordinary', it's also not hard for someone with a little technical ability. I just joined the advertised WiFi network from the Tesla Energy Gateway and pointed my browser to the default gateway address. It showed a web version of what my app would.

Also, the gateway must have a cell connection as well, because I had cell service through Verizon and could access my Powerwall data through the app when on cell. Accessing through WiFi, as above, showed "connected to Tesla" even though Comcast was down.

 

[bmah]

...'custom code'....great for the 'ordinary' homeowner...

Sorry, I didn't mean this is a solution for everybody...I'm just saying that the means exists to get that information locally in the face of no Internet connectivity. I actually did write some software to poll that API and use some other open-source software (InfluxDB, Grafana) to make some nice graphs...and I had those Web pages up pretty much all the time during the power shutoff.

When my local neighborhood loses power, in maybe 10-30 minutes, Comcast goes down, likely as some kind of backup battery on a coax amp or switch runs down. Makes me sort of wonder about going with a satellite ISP as redundancy.

Starlink.

I have AT&T fiber at my house (resold by sonic.net, although I think that fact is irrelevant). It stayed up the whole time...not sure what active components there are in that sort of network that need power. Our cell phones (AT&T) worked as far as I could tell.

Bruce.