New Solar Panel Project

[Brandonn22]

Hi all! I am located in Georgetown, TX and this is just north of Austin, TX. Placed an order on August 13th for 12.75 kW Solar Panels and 1 Powerwall. As soon as I placed my order, I completed the home assessment and requested for approval by my HOA. My design just came in this past Friday (8/27). I approved the design yesterday (8/28) and applied for the credit check. Credit check was approved within minutes and now waiting for the next steps. Hope to keep everybody updated on the experience to see how this goes.

The only thing I would say so far is that there is really no interaction with any real people. I had to personally email Tesla energy to get my project advisor’s name and contact information. The project advisor has never reached out to me. I only reached out to say hi and see if he would know exactly how long my design would take as the estimate gives a broad window. You just get emails to take action for any steps that the buyer must do, which is your online Tesla account. The experience isn’t very personal, but not bad. We’ll see how the rest goes.

 

[jjrandorin]

If you are actually wanting to back up more than lights and refrigerators, you likely want one more powerwall to go with a PV system of that size.

 

[holeydonut]

Yeah, more batteries is always better.... but the costs are rather nutty too.

I assume for a 12.75 kWp DC system that you'll get one 3.8 kW and one 7.6 kW Tesla inverter. I forget, do the Tesla inverters de-rate themselves, so the system can still charge a single Powerwall at presumably 5kW if the utility goes offline near high noon? Or in this case would the 7.6 kW unit simply go offline and he'd have the 3.8 kW inverter for backup charging?

 

[jjrandorin]

Yeah, more batteries is always better.... but the costs are rather nutty too.

I assume for a 12.75 kWp DC system that you'll get one 3.8 kW and one 7.6 kW Tesla inverter. I forget, do the Tesla inverters de-rate themselves, so the system can still charge a single Powerwall at presumably 5kW if the utility goes offline near high noon? Or in this case would the 7.6 kW unit simply go offline and he'd have the 3.8 kW inverter for backup charging?

I think that depends on what strings are connected where, as to how much of the system is still "active" in a power outage. With only 1 powerwall, however, one cant use any 240v appliance at all (unless this is changed with powerwall +), so it would really be for lights and fridges (and regular outlets).

 

[holeydonut]

I think that depends on what strings are connected where, as to how much of the system is still "active" in a power outage. With only 1 powerwall, however, one cant use any 240v appliance at all (unless this is changed with powerwall +), so it would really be for lights and fridges (and regular outlets).

Yeah I agree that single Powerwall backups are basically only useful for a refrigerator, some lights, and maybe an HVAC air handler. Probably doesn't matter what his inverters are doing since he won't be using much power lol.

Oh... random question...

Let's pretend he puts an EV Charging outlet on the backup load side of the single Powerwall. Could the homeowner charge their EV at 240v assuming the sun were up and feeding energy into the EV during a blackout?

 

[arnolddeleon]

Let's pretend he puts an EV Charging outlet on the backup load side of the single Powerwall. Could the homeowner charge their EV at 240v assuming the sun were up and feeding energy into the EV during a blackout?

Yes

 

[Vines]

With only 1 powerwall, however, one cant use any 240v appliance at all (unless this is changed with powerwall +), so it would really be for lights and fridges (and regular outlets).

I have seen this stated a couple times now and do not agree. The Powerwall 2 AC is a 240v device and so can power a 240v load up to its rating.
While a single Powerwall 2 AC will not have much ability to start a 240v motor, there is plenty of power for more average 240v appliances. With the incoming firmware upgrade, more motors and AC units can be used with a single or 2 Powerwalls.

Granted, I think the balance of the legs is important and that if either of the 2 legs goes over the 24A limit then the Powerwall trips. I am not sure how tolerant it is to unbalanced loads.

 

[ericl]

Yeah I agree that single Powerwall backups are basically only useful for a refrigerator, some lights, and maybe an HVAC air handler. Probably doesn't matter what his inverters are doing since he won't be using much power lol.

Oh... random question...

Let's pretend he puts an EV Charging outlet on the backup load side of the single Powerwall. Could the homeowner charge their EV at 240v assuming the sun were up and feeding energy into the EV during a blackout?

I tested backup mode today and I am able to run/start my HVAC off the single powerwall+. However during a real blackout I will probably turn the HVAC off at night since it runs at 4kw/hr.

 

[jjrandorin]

I have seen this stated a couple times now and do not agree. The Powerwall 2 AC is a 240v device and so can power a 240v load up to its rating.
While a single Powerwall 2 AC will not have much ability to start a 240v motor, there is plenty of power for more average 240v appliances. With the incoming firmware upgrade, more motors and AC units can be used with a single or 2 Powerwalls.

Granted, I think the balance of the legs is important and that if either of the 2 legs goes over the 24A limit then the Powerwall trips. I am not sure how tolerant it is to unbalanced loads.

Thanks for the correction. I am not sure where I got that understanding, but was under the impression that one powerwall was not sufficient to start up 240V loads (not talking about powerwall + but neither were you).

 

[Brandonn22]

Yeah, more batteries is always better.... but the costs are rather nutty too.

I assume for a 12.75 kWp DC system that you'll get one 3.8 kW and one 7.6 kW Tesla inverter. I forget, do the Tesla inverters de-rate themselves, so the system can still charge a single Powerwall at presumably 5kW if the utility goes offline near high noon? Or in this case would the 7.6 kW unit simply go offline and he'd have the 3.8 kW inverter for backup charging?

Yeah, I would have added another power wall if it were not for the costs.

 

[Brandonn22]

I tested backup mode today and I am able to run/start my HVAC off the single powerwall+. However during a real blackout I will probably turn the HVAC off at night since it runs at 4kw/hr.

Glad to hear the HVAC starts off a single powerwall+

 

[jjrandorin]

Glad to hear the HVAC starts off a single powerwall+

I would be really (really really) careful of extrapolating anyones AC start up experience with what you may or may not experience. One thing I am sure of, is that there are tons of different AC systems, with different startup load needs, and just because system A starts in one place, it has zero bearing on whether system B will start up in another place.

If you plan on having the AC backed up, thats something you will need to be very clear about with tesla (or whomever your installer company is, if not tesla). Do not make any assumption that "it will just work" or "they will make it work". There are plenty of people, even on this board, who expected AC to work in the backup, but it didnt in their particular situation, even with things like soft starts, or hard starts, etc.

 

[yblaser]

Thanks for the correction. I am not sure where I got that understanding, but was under the impression that one powerwall was not sufficient to start up 240V loads (not talking about powerwall + but neither were you).

When choosing your configuration during ordering the Tesla website said, and may still say (I haven't checked), that one powerwall would support ordinary 120VAC loads while two powerwalls would support additional 240VAC loads. I think they were trying to frame it in what an ordinary layperson would understand but can see that the information could be easily misconstrued. As Vines says the spec sheet says the powerwall outputs 240VAC and can support up to 100% load imbalance among the split phase. I would assume it can only support 1/2 its rated power on each individual hot output given there would only be a 30A breaker on each hot line.

 

[BGbreeder]

I have seen this stated a couple times now and do not agree. The Powerwall 2 AC is a 240v device and so can power a 240v load up to its rating.
While a single Powerwall 2 AC will not have much ability to start a 240v motor, there is plenty of power for more average 240v appliances. With the incoming firmware upgrade, more motors and AC units can be used with a single or 2 Powerwalls.

Granted, I think the balance of the legs is important and that if either of the 2 legs goes over the 24A limit then the Powerwall trips. I am not sure how tolerant it is to unbalanced loads.

I agree. The Powerwall specification placard specifically calls out the specification that the max current is 24A at 240, and then lower down in the phase section, that for 200, 208, and 240V it is 2W, neutral, PE (protective earth), which would suggest to me that each 120V leg is capped at 24A. It also calls out that the inverter topology is isolated, which means that the neutral must deal with the imbalance on the two 120V phases of the 240V.

All the best,

BG

 

[lchen6]

Hi all! I am located in Georgetown, TX and this is just north of Austin, TX. Placed an order on August 13th for 12.75 kW Solar Panels and 1 Powerwall. As soon as I placed my order, I completed the home assessment and requested for approval by my HOA. My design just came in this past Friday (8/27). I approved the design yesterday (8/28) and applied for the credit check. Credit check was approved within minutes and now waiting for the next steps. Hope to keep everybody updated on the experience to see how this goes.

The only thing I would say so far is that there is really no interaction with any real people. I had to personally email Tesla energy to get my project advisor’s name and contact information. The project advisor has never reached out to me. I only reached out to say hi and see if he would know exactly how long my design would take as the estimate gives a broad window. You just get emails to take action for any steps that the buyer must do, which is your online Tesla account. The experience isn’t very personal, but not bad. We’ll see how the rest goes.

How is your HOA approval process? We only have 3 units in our HOA, I'm trying to gauge on how to get the approval and feed Tesla on what they need?