2 Powerwall+ vs 1 Powerwall+ and one regular Powerwall

[jriv]

Hello! Im looking to instal a 10.2kw DC system consisting of 24 425w panels. My installer is offering me to option of getting 2 Powerwall+ or 1 Powerwall+ with the second Powerwall being the regular Powerwall 2.

As I understand, the Powerwall+ has a 7.6kw inverter that may be maxed out (clipping?) with my 10.2kw system but not by a lot.

I am failing to see the differences between the two options. Would getting the two Powerwall+ means that since I’ll have two inverters I can have half the PV capacity (5.1kw DC) attached to each one and overall daily production can be higher since I will no be experimenting clipping over 7.6kw?

Also, I want to have the option to expand the PV capacity in the future.

Does anybody have a system with two Powerwall+ instead of one of each?

I am really struggling to understand the main difference between the two options.

If anybody can help, I would be grateful.

Thaks

 

[Rocket_man]

I just had my system installed not long ago, still pre-inspection. And I'm sure there are others that know far more than I do. I was talking to the guy wiring up the panels. I noticed they shifted the panels higher on my roof and it looked like I could have gotten more panels on the roof. But I also mentioned my 14.8kw system would have needed another inverter if I added more panels (with two PW + I have 7.6kw x 2). But he said no that would not have been needed because the inverters can work well above their nameplate. He didn't know the number but it was at least 120%. So my guess is with your system you won't see much clipping if any. And that would only be on the sunniest days mid-day.

But my two-cents... if you think you want to go bigger... go big now. Don't wait to add later. Just get it all done at one shot. Tesla designed mine and with 14.8kw, 37 x 400 watt panels, they spec'd two PW+ Still trying to decide if I went big enough or not. I went as big as my wallet wanted me to.

edit: I'm not sure of the fact that I have two PW+ and some panels going to each, if this means I have some redundancy if one of the inverters went out. I'm not sure I could charge both batteries from one inverter, but it might be a reliability benefit to having two. If someone knows if I can charge both batteries from one inverter (and half my panels), please let me know.

 

[jriv]

I just had my system installed not long ago, still pre-inspection. And I'm sure there are others that know far more than I do. I was talking to the guy wiring up the panels. I noticed they shifted the panels higher on my roof and it looked like I could have gotten more panels on the roof. But I also mentioned my 14.8kw system would have needed another inverter if I added more panels (with two PW + I have 7.6kw x 2). But he said no that would not have been needed because the inverters can work well above their nameplate. He didn't know the number but it was at least 120%. So my guess is with your system you won't see much clipping if any. And that would only be on the sunniest days mid-day.

But my two-cents... if you think you want to go bigger... go big now. Don't wait to add later. Just get it all done at one shot. Tesla designed mine and with 14.8kw, 37 x 400 watt panels, they spec'd two PW+ Still trying to decide if I went big enough or not. I went as big as my wallet wanted me to.

edit: I'm not sure of the fact that I have two PW+ and some panels going to each, if this means I have some redundancy if one of the inverters went out. I'm not sure I could charge both batteries from one inverter, but it might be a reliability benefit to having two. If someone knows if I can charge both batteries from one inverter (and half my panels), please let me know.

Hey thanks for the info!
It is my understanding that if one of the inverters goes bad, the system will continue operating and charging both batteries from the other inverter alone.
Regarding the inverter being able to handle more than 7.6kw Tesla does recommend a maximum DC/AC ratio of 1.7, which I consider to be a lot! That means that you can put up to 12.92kw per inverter.

Many local companies here use a max DC/AC ratio of 1.4 which translates to a max of 10.64kw pero inverter which is less wasteful.

It is my understanding that having a higher DC to AC ratio will allow your system to reach peak production (7.6kw) earlier in the day and sustain later in the evening and also it will be more likely to hit peak in overcast conditions but it won’t enable you to go higher than 7.5, hence the “clipping” issue.

In my case, I was looking at 10.2kw before given the option for two PW+, however since I want to have the option of expanding in the future if needed, I am thinking about going with two PW+ and 12kw allowing me to expand to 15kw+ if necessary.

Being able to increase capacity is a big deal for me since I’ll be installing in a new house and I am not one hundred percent confident about how high will my consumption be.

 

[craigcabrey]

If there is no cost difference, get 2 PW+. Most installers won't modify an existing system, but you can always add additional panels yourself with all the hard bits already done.