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FYI - Managing Power during an Outage

Bruce Person

Red Rover
Mar 2, 2020
41
15
95437
When the Tesla Gateway detects the grid is down, excess solar power is used only to charge the PowerWalls. And when the PowerWalls get near to full, the Gateway changes the power frequency above 60Hz, which causes the solar power inverters to shut off, so no power from the solar panels will even be sent into the Gateway.

During an outage - no power is sent to the grid.

---

We live in the Houston area. Generators will usually run off the same gas lines that go into the houses for use in appliances and HVAC systems.

We have the only solar panels on our street. Two houses next to us have gas generators. When we lost power, we switched over to our PowerWalls - and for those houses, their generators kicked on - and you can definitely hear them running.

As far as I know, our area did not have any problems with natural gas lines.

Our concern was that when our power went out, the "authorities" were indicating new outages could last days - and with the prospect of little sun for the next day, we took steps to drastically reduce consumption, just in case we needed to run off the PowerWalls for more than 24 hours. Our neighbors with the generators were fine and only had to worry if the natural gas lines went down - which haven't happened as long as I can remember in our area - even after hurricanes, the natural gas lines have worked.

Question: Does your neighborhood allow large propane tanks using underground lines to supply the generator/house?
 

DuaneCastles

New Member
Feb 22, 2021
3
3
Selah, Washington
So the solar array is just cut off from the grid during an outage but charges the powerwalls?
You were told, or understood incorrectly. One of the whole points of having powerwalls (or other batteries) when you have solar is so that solar power has someplace to go when there is no grid. Powerwalls absolutely postivitely 100% do charge from solar during a power outage.

Thats the way the system works everywhere (not just texas).

I am not making any judgement at all about which backup technology is better because its a personal choice for each person, and both have their pros and cons. I just wanted to provide you with correct information about solar + powerwalls and charging during an outage.
Thank you. I appreciate the info. For us, having the whole house backup generator works great.
 
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5-Cents

New Member
Sep 11, 2020
4
0
St Louis, MO
It makes me sad that people can't get out of their garage due to a power outage. Now, I have battery backup on my openers, but as far as I know every single garage door opener I've ever seen has a handle you can pull to disengage the opener. Then you just lift the door manually. Unless you are seriously physically challenged, this should not have been a problem.
 

h2ofun

Active Member
Aug 11, 2020
2,088
324
auburn, ca
It makes me sad that people can't get out of their garage due to a power outage. Now, I have battery backup on my openers, but as far as I know every single garage door opener I've ever seen has a handle you can pull to disengage the opener. Then you just lift the door manually. Unless you are seriously physically challenged, this should not have been a problem.
Yep, that was the issue in the fires. Older folks who either could not pull the cord, assuming they knew it was there, and were not able to physically push up the garage door. No matter, it is code now
 
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pete8314

Vendor
Jun 4, 2012
2,358
658
DFW, ex UK
We were out of power for about 40hrs in total, in 3 chunks. The panels & single Powewall helped us limp through, but I'll be adding another PW to help support more circuits, including the pool, which stopped at 3 in the morning, so we've sustained at least $2k of damage there (equipment), if the tile starts falling off, add another $2k minimum :-/

We were on Griddy, jumped off on the Friday as the storm was taking hold, but back on now. Wrote a blog post about it here, if anyone's interested. We learned quite a bit about how PW actually works during a prolonged outage, in tandem (or not) with solar generation.
 

rgedad

Member
Apr 6, 2018
63
70
Fort Worth, TX
raynag01
Do some areas in Texas allow for generators?

So Yes, Texans does permit generators, at least in Fort Worth.( I am in the western suburbs
We moved to Texas some 5 years ago from the far north - so used to the cold, not so much the heat. 2 Years ago - just as we purchased our MX, while in the heat of the summer, My wife was concerned about having power outages in the heat of the Texas summer. I installed a 20KW Briggs & Stratton Natural Gas Generator. It came on a couple of times during the intervening years, but nothing dramatic. The generator is big enough to power both of my AC units (5 ton and 4 ton) and still charge up the MX and the rest of the house (excepting the dryer & oven). I debated getting Propane vs Natural gas (I like the standalone aspect) But; 1) I am in Texas right - lots of Natural gas, 2) The image of a large 500 gallon propane tank did not pass the house image review team (Spousal unit). The unit self disconnects from the main while the generator is running (20 second drop-out), and reconnects to the main when prime power becomes active.

During this last week with all the outages in and around Fort Worth my lights never even flickered, nor did I lose water. All around us (Western suburbs of Fort Worth) people were out of power for days, and some still do not have drinking water.

My generator is not located really near any neighbors - maybe 80 feet away. During this outage I was concerned when I understood the power plants were shutting down due to natural gas line freezing, but our house is heated by natural gas, as is our fireplace with no issues. The generator did it's weekly test run on Tuesday with no issues.

Truth be told, I kind of wish I had lost power - just to validate my deciding to drop the $10K on the generator and to show I had not just squandered the cash on unnecessary emergency equipment. I do feel the only reason our street did not lose power was because of my generator.
 
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bob_p

Active Member
Apr 5, 2012
3,664
2,787
When we had our system installed, I simulated some grid power outages to verify the system would provide us the backup power we wanted. The two scenarios I tested (by throwing the breaker that disconnected the grid power):
  1. Unplanned short-term outage: These outages typically last from minutes to a few hours. We might or might not be at home (to turn off non-essential devices). While the grid was offline, turned everything on all of the large power consuming devices to verify we could stay below the sustained power provided by 4 PowerWalls (20KW). With this testing, we verified that as long as we weren't running our electric ovens, we stayed below 20KW - which included refrigerators, 2 pool pumps, 3 air conditioners, ... Since we would only run the electric ovens when we're at home - we're not planning to run the ovens when running off-grid.

  2. Anticipated long-term outage: These outages we planned for after a hurricane - and would likely for longer than a day. Storm Watch would have filled the PowerWalls to 100% before the outage. We would be home when the outage occurred, and able to turn off enough devices to ensure we'd be able to run off the PowerWalls for days. And since these storms are typically followed by sunny days - during the late summer/early fall, we would likely get considerable charging each day of the PowerWalls. We would probably turn off 2 of our 3 HVAC systems and increase the temperature on the remaining system. Pool equipment run time would be reduced - and we wouldn't do any EV charging. If necessary we'd turn the last HVAC system off and open windows. Based on testing, we have confidence we can operate off-grid - for days - in warm weather.
The scenario we didn't expect in Houston was an anticipated long-term outage during very cold weather - which changes the power consumption considerably - because HVAC will be needed to keep the house and interior pipes warm AND we would need to run the pool pumps almost continuously to prevent the lines and pumps from freezing. Plus, during winter storms, it's likely there will be little or no sun for days, making it more critical to reduce power consumption as much as possible to stretch the fully charged PowerWalls as long as possible. Based on our testing, we have less confidence our 4 PowerWalls could last us for days - if we have to periodically run a heater or the pool pumps.

For PowerWall owners, if you haven't gone through planning for unplanned or anticipated outages, would strongly recommend doing so - so that when you do have an outage - you know what your system can handle - and what devices/circuits you should turn off to get through the outage.
 
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h2ofun

Active Member
Aug 11, 2020
2,088
324
auburn, ca
When we had our system installed, I simulated some grid power outages to verify the system would provide us the backup power we wanted. The two scenarios I tested (by throwing the breaker that disconnected the grid power):
  1. Unplanned short-term outage: These outages typically last from minutes to a few hours. We might or might not be at home (to turn off non-essential devices). While the grid was offline, turned everything on all of the large power consuming devices to verify we could stay below the sustained power provided by 4 PowerWalls (20KW). With this testing, we verified that as long as we weren't running our electric ovens, we stayed below 20KW - which included refrigerators, 2 pool pumps, 3 air conditioners, ... Since we would only run the electric ovens when we're at home - we're not planning to run the ovens when running off-grid.

  2. Anticipated long-term outage: These outages we planned for after a hurricane - and would likely for longer than a day. Storm Watch would have filled the PowerWalls to 100% before the outage. We would be home when the outage occurred, and able to turn off enough devices to ensure we'd be able to run off the PowerWalls for days. And since these storms are typically followed by sunny days - during the late summer/early fall, we would likely get considerable charging each day of the PowerWalls. We would probably turn off 2 of our 3 HVAC systems and increase the temperature on the remaining system. Pool equipment run time would be reduced - and we wouldn't do any EV charging. If necessary we'd turn the last HVAC system off and open windows. Based on testing, we have confidence we can operate off-grid - for days - in warm weather.
The scenario we didn't expect in Houston was an anticipated long-term outage during very cold weather - which changes the power consumption considerably - because HVAC will be needed to keep the house and interior pipes warm AND we would need to run the pool pumps almost continuously to prevent the lines and pumps from freezing. Plus, during winter storms, it's likely there will be little or no sun for days, making it more critical to reduce power consumption as much as possible to stretch the fully charged PowerWalls as long as possible. Based on our testing, we have less confidence our 4 PowerWalls could last us for days - if we have to periodically run a heater or the pool pumps.

For PowerWall owners, if you haven't gone through planning for unplanned or anticipated outages, would strongly recommend doing so - so that when you do have an outage - you know what your system can handle - and what devices/circuits you should turn off to get through the outage.
This is why I also have a generator for your last scenario with a 500 gallon propane source. May never need it but, I am ready for
the 500 year perfect storm
 
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jboy210

Supporting Member
Dec 2, 2016
4,926
3,017
Northern California
When we had our system installed, I simulated some grid power outages to verify the system would provide us the backup power we wanted. The two scenarios I tested (by throwing the breaker that disconnected the grid power):
  1. Unplanned short-term outage: These outages typically last from minutes to a few hours. We might or might not be at home (to turn off non-essential devices). While the grid was offline, turned everything on all of the large power consuming devices to verify we could stay below the sustained power provided by 4 PowerWalls (20KW). With this testing, we verified that as long as we weren't running our electric ovens, we stayed below 20KW - which included refrigerators, 2 pool pumps, 3 air conditioners, ... Since we would only run the electric ovens when we're at home - we're not planning to run the ovens when running off-grid.

  2. Anticipated long-term outage: These outages we planned for after a hurricane - and would likely for longer than a day. Storm Watch would have filled the PowerWalls to 100% before the outage. We would be home when the outage occurred, and able to turn off enough devices to ensure we'd be able to run off the PowerWalls for days. And since these storms are typically followed by sunny days - during the late summer/early fall, we would likely get considerable charging each day of the PowerWalls. We would probably turn off 2 of our 3 HVAC systems and increase the temperature on the remaining system. Pool equipment run time would be reduced - and we wouldn't do any EV charging. If necessary we'd turn the last HVAC system off and open windows. Based on testing, we have confidence we can operate off-grid - for days - in warm weather.
The scenario we didn't expect in Houston was an anticipated long-term outage during very cold weather - which changes the power consumption considerably - because HVAC will be needed to keep the house and interior pipes warm AND we would need to run the pool pumps almost continuously to prevent the lines and pumps from freezing. Plus, during winter storms, it's likely there will be little or no sun for days, making it more critical to reduce power consumption as much as possible to stretch the fully charged PowerWalls as long as possible. Based on our testing, we have less confidence our 4 PowerWalls could last us for days - if we have to periodically run a heater or the pool pumps.

For PowerWall owners, if you haven't gone through planning for unplanned or anticipated outages, would strongly recommend doing so - so that when you do have an outage - you know what your system can handle - and what devices/circuits you should turn off to get through the outage.
Power outage is reason #120 why I never installed a pool. #1 was maintenance. We were a slave to that thing when we were kids.
 

gpez

Member
Apr 25, 2019
653
530
USA
We were out of power for about 40hrs in total, in 3 chunks. The panels & single Powewall helped us limp through, but I'll be adding another PW to help support more circuits, including the pool, which stopped at 3 in the morning, so we've sustained at least $2k of damage there (equipment), if the tile starts falling off, add another $2k minimum :-/

We were on Griddy, jumped off on the Friday as the storm was taking hold, but back on now. Wrote a blog post about it here, if anyone's interested. We learned quite a bit about how PW actually works during a prolonged outage, in tandem (or not) with solar generation.

@pete8314 I read your blog post - 82% is way too low for the Powerwall to shut off your PV. I'm guessing something is misconfigured.

Also take a look at the power frequency settings on your PV inverter which can gradually reduce the power produced by your solar as the Powerwall fills up rather than see-sawing on and off.
 

Bruce Person

Red Rover
Mar 2, 2020
41
15
95437
raynag01


So Yes, Texans does permit generators, at least in Fort Worth.( I am in the western suburbs
We moved to Texas some 5 years ago from the far north - so used to the cold, not so much the heat. 2 Years ago - just as we purchased our MX, while in the heat of the summer, My wife was concerned about having power outages in the heat of the Texas summer. I installed a 20KW Briggs & Stratton Natural Gas Generator. It came on a couple of times during the intervening years, but nothing dramatic. The generator is big enough to power both of my AC units (5 ton and 4 ton) and still charge up the MX and the rest of the house (excepting the dryer & oven). I debated getting Propane vs Natural gas (I like the standalone aspect) But; 1) I am in Texas right - lots of Natural gas, 2) The image of a large 500 gallon propane tank did not pass the house image review team (Spousal unit). The unit self disconnects from the main while the generator is running (20 second drop-out), and reconnects to the main when prime power becomes active.

During this last week with all the outages in and around Fort Worth my lights never even flickered, nor did I lose water. All around us (Western suburbs of Fort Worth) people were out of power for days, and some still do not have drinking water.

My generator is not located really near any neighbors - maybe 80 feet away. During this outage I was concerned when I understood the power plants were shutting down due to natural gas line freezing, but our house is heated by natural gas, as is our fireplace with no issues. The generator did it's weekly test run on Tuesday with no issues.

Truth be told, I kind of wish I had lost power - just to validate my deciding to drop the $10K on the generator and to show I had not just squandered the cash on unnecessary emergency equipment. I do feel the only reason our street did not lose power was because of my generator.
We too have a 200 amp transfer switch to make going on and off the grid seamless. I do wish I had the newer 24kw air cooled Generac because the power does seem to waver. However the real worth of the generator is the true piece of mind you get during storms or planned power outages. No matter how infrequent it comes on, we always comment to each other what a good decision it was to install it. Ours is in a grove of trees some distance from the house so the running noise doesn't bother us but I know if we walk around outside you can still hear it. With propane I still need to check the tank level from time to time. Would an underground tank solve the spousal unit issue? Are underground tank allowed?
 
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h2ofun

Active Member
Aug 11, 2020
2,088
324
auburn, ca
We too have a 200 amp transfer switch to make going on and off the grid seamless. I do wish I had the newer 24kw air cooled Generac because the power does seem to waver. However the real worth of the generator is the true piece of mind you get during storms or planned power outages. No matter how infrequent it comes on, we always comment to each other what a good decision it was to install it. Ours is in a grove of trees some distance from the house so the running noise doesn't bother us but I know if we walk around outside you can still hear it. With propane I still need to check the tank level from time to time. Would an underground tank solve the spousal unit issue? Are underground tank allowed?
Totally agree with you peace of mind comment, for me with the boss. I have had a number of power outages for power pole replacements. Have another one tomorrow. With the generator, I know I can just turn it on when needed.

And if I am in the dead of winter with a long power outage, and batteries cannot be recharged, again, I know the generator is ready to pick up the slack.

For many they say its a waste of money. For me, what others spend money on I can say the same :)
 

Merle

Member
Apr 5, 2019
155
125
Tahoe
Have to wonder about those people who also got smacked for the "flexible" electricity rate costs in the past, and now sitting on $5000-15,000 if not higher electricity bills for the past month.

It was cheap in the short term, and for the most part, but maybe pulling out a gas (or NG) generator to power the home through this would have been wise?

* Firewood is renewable
* Natural gas is plentiful
* A portable generator runs less $100 per 1kW when you plan ahead

For those with a NG generator (or Propane), is your electricity rate the same or is there a time-of-use consideration which would make it make sense to disconnect from the grid and just use your own power supply?

And for those with the Tesla Solar PV system ... are you expecting a big check as the wholesale prices skyrocketed during the outages or is it a "break even" even now (aka, you didn't get to cash in)?
 

gpez

Member
Apr 25, 2019
653
530
USA
Have to wonder about those people who also got smacked for the "flexible" electricity rate costs in the past, and now sitting on $5000-15,000 if not higher electricity bills for the past month.

It was cheap in the short term, and for the most part, but maybe pulling out a gas (or NG) generator to power the home through this would have been wise?

* Firewood is renewable
* Natural gas is plentiful
* A portable generator runs less $100 per 1kW when you plan ahead

For those with a NG generator (or Propane), is your electricity rate the same or is there a time-of-use consideration which would make it make sense to disconnect from the grid and just use your own power supply?

And for those with the Tesla Solar PV system ... are you expecting a big check as the wholesale prices skyrocketed during the outages or is it a "break even" even now (aka, you didn't get to cash in)?

Isn't this exactly the point of paying wholesale market rates? Pull from the grid when it's cheap, produce locally when it's expensive which in turn reduces demand and thus prices, lowering overall costs?

IMO we should be expecting those that are on wholesale rate plans to be paid wholesale rates for the power they produce!
 

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