First actual loss of grid - success for Powerwalls!

[Parzival]

I experienced this only when I have excess load in my home for the PowerWall system, and the power-outage causes some big loads to drop (such as the dryer, etc.), which don't come back on when the PowerWalls come back on. I was only able to duplicate this behavior by turning off one of my PowerWalls, to handicap the system's total capacity; I don't have this problem when both my PowerWalls are on. Do you have heavy loads that do not work with only the PowerWalls and are jettisoned for backup use?

Otherwise, if you don't find some big devices being shedded through this behavior, I think you have something wrong in your installation. I find the seamless nature of the cutover to be one of the features of the Gateway.

Another possibility is that the electronics needed in your setup are different than those used in ours because you have higher current connections. How many amps is the breaker to and from the Gateway?

No heavy loads, and I have whole home backup. My home's typical consumption is 0.2-0.6kW unless charging the car, running A/C, etc.; The gateway is my main disconnect and has a 200A breaker.

I've noticed that when the PW is in self-consumption mode and I force a grid outage, the transition is seamless. It's when I go off-grid in backup mode that there's a small hiccup, but it seems better recently--it's not enough for computers, TV, or other electronics to notice. When going back on-grid, it's always seamless.

Tesla installed a SureStart on my A/C unit a few days ago, and now I can run off grid completely. I've had the grid turned off for a few days and it's amazing how well everything works.

 

[Ulmo]

No heavy loads, and I have whole home backup. My home's typical consumption is 0.2-0.6kW unless charging the car, running A/C, etc.; The gateway is my main disconnect and has a 200A breaker.

I've noticed that when the PW is in self-consumption mode and I force a grid outage, the transition is seamless. It's when I go off-grid in backup mode that there's a small hiccup, but it seems better recently--it's not enough for computers, TV, or other electronics to notice. When going back on-grid, it's always seamless.

Tesla installed a SureStart on my A/C unit a few days ago, and now I can run off grid completely. I've had the grid turned off for a few days and it's amazing how well everything works.

I just read the literature from SureStart at http://hypereng.com/literature/SC5600HM-SureStart-Specification-Catalog.pdf, and it seems like once this product is properly installed on all compressors and other high-in-rush starting devices (such as motors under load, such as pumps), then homes with those devices should work fine with properly sized PowerWall 2 installations.

 

[Bigtanuki]

I experienced this only when I have excess load in my home for the PowerWall system, and the power-outage causes some big loads to drop (such as the dryer, etc.), which don't come back on when the PowerWalls come back on. I was only able to duplicate this behavior by turning off one of my PowerWalls, to handicap the system's total capacity; I don't have this problem when both my PowerWalls are on. Do you have heavy loads that do not work with only the PowerWalls and are jettisoned for backup use?

Otherwise, if you don't find some big devices being shedded through this behavior, I think you have something wrong in your installation. I find the seamless nature of the cutover to be one of the features of the Gateway.

Another possibility is that the electronics needed in your setup are different than those used in ours because you have higher current connections. How many amps is the breaker to and from the Gateway?

I'm curious if anyone else has seen this load shed behavior for large loads on transfer. I saw similar behavior when I did a test while charging the MS. I was in backup mode not self-consumption so that may have made a difference in behavior but that doesn't seem likely. In my case I had only two PW on line so the ~12 kW draw from the car exceeded the system capacity. Once the system flopped over to the battery the charger dropped off and didn't auto reconnect and start charging. I'm not sure that it would disconnect with 3 PW in service so that the 12 kW would be less than system capacity.

This has direct bearing on one of my scenarios for loss of grid. Imagine you are charging the car (off-peak) while asleep and it's drawing off the batteries down to the reserve. A loss of grid occurs and now the reserve capacity of the PW is enabled. Without any notice the system is now capable of drawing all of the reserve capacity leaving you without power. I can see that this might affect the ability of your solar to self start once the sun comes up leaving you with no power options.

Anyone out there run any tests that might confirm these behaviors?

 

[FlyRealFast]

Could you be more specific on sizing?Specifically # of BTU's of A/C, kW of panels, and kWh of batteries?

A 2000 sq ft home requires an approximately 3 ton unit. This is roughly 36,000 BTU's requiring ~10kW per hour of power. So even running only 10 hours each day you would need 10kWh production. Back of the envelope panel requirements...20kW or about 80 panels.

That's a big consumer installation. Probably bigger than the roof on a 2000 sq ft house. Now if you're only thinking of using a small room A/C unit, say 8000BTU, then I think it's doable with a normal consumer installation.

FWIW I'l offer these data points from our experience over the past two years:

 

[FlyRealFast]

Could you be more specific on sizing?Specifically # of BTU's of A/C, kW of panels, and kWh of batteries?

A 2000 sq ft home requires an approximately 3 ton unit. This is roughly 36,000 BTU's requiring ~10kW per hour of power. So even running only 10 hours each day you would need 10kWh production. Back of the envelope panel requirements...20kW or about 80 panels.

That's a big consumer installation. Probably bigger than the roof on a 2000 sq ft house. Now if you're only thinking of using a small room A/C unit, say 8000BTU, then I think it's doable with a normal consumer installation.

FWIW I'll share the following sizing and performance data from our system in Florida which has been online for about two years now:

- 2,600 SF home, pool, electric always-on spa heater, 5 ton AC/heat pump (provides all heating and cooling)
- 15KW solar PV generator, 54 panels, 3 strings of 18 panels, one 10KW and one 5KW inverter
- Avg daily generation = 75KWh
- Avg monthly generation = 2MWh
- Avg daily home energy use (all loads) = 50KWh in the 6 cooler months and 80 KWH in the 6 hot months

As we plan for future PW2s it seems like 3 units would run the entire home for almost 24 hours (all loads) in the cooler months with zero sun. Given that were always generating some energy during the day (even on cloudy days) and given that some loads could be shed in the event of an extended grid failure, two PW2s seems like the right starting point.

Pat