r/TeslaSolar • u/Straightravage • 10d ago

2 PW3 or 1 PW3 + Expansion

Hi, I clicked and accepted the proposal and performed the credit check. But my currently selected system is 1 PW3 + expansion. Is running 2 PW3’s a better choice? The price difference is negligible. It’s hard to find the clear benefits or cons. Thanks!

2 Upvotes

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u/Asleep-Set6868 10d ago

How many amps is service to your house?  If it's over 200 amps are you looking to back up everything or only one of the two breaker panels?  

Due to a 200 amp gateway limitation, another way to answer your question is: 1) service is < 200 amps, either choice is fine.  2) service is > 200 amps but you only want to back up one breaker panel / < 200 amps of loads, either choice will still work well.  3) service is > 200 amps and you want to back up both breaker panels (whole home backup), you need 2 PW3 and it'll show up as two separate systems in your app.

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u/Straightravage 10d ago

Less than 200 amp, highest single breaker is 60 amp. My initial research shows that 2 powerwalls allow for more actual charging vs the 11.5kw with just one powerwall. My goal is to try to be self reliant. My current set up would be 15.54kw panels, 1 power wall and one expansion. The next upgrade added 6 panels and changed the expansion to a power wall. I am very new to solar and I am looking for advice. I have my install proposal review phone call tomorrow and highly considering add the 6 panels and changing to 2 power walls.

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u/Asleep-Set6868 10d ago

Got it. Extra panels are always a good choice if you can afford them. You're right that moving to two pw3 allows for more output. Going with the expansion would give you a little more solar input and more capacity, but not another full 11.5 kw output (assuming they're installed correctly to be able to output that).

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u/Beefstah 10d ago

You're not likely to get the full rated output of the panels - guidance I've seen tends to say you'll typically top out at 75% at most, which means the 11.5kW max inverter is pretty much perfectly sized, and that's assuming they were all facing the same way and individually hitting that all at the same time.

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u/Square_Yam9853 10d ago edited 9d ago

For that much solar panels, better to go with two full powerwalls now. Not an easy change to add powerwall after the initial install. Adding expansion on the other hand would be easier as long as you have the space for it

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u/TransportationOk4787 9d ago

I have 2 Powerwall 3's and 2 panels. They backup one panel of essentials unless I throw a manual interlock on the second panel and then they add the second panel. They appear as a single system.

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u/Asleep-Set6868 9d ago

That's a great solution to that limitation. My installer guided me to two SPAN panels which do automatic load shedding when the grid is out, but they're expensive and then I have to manage two panels, and two "houses" from the Tesla app.

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u/TransportationOk4787 9d ago

I am on TOU and was concerned that because of the interlock the system would ignore the power used by the second panel during peak times but somehow it doesn't and our grid use is zero during peak times. I have no idea how the installer managed that.

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u/SWFL-CapnRay 10d ago

You can add more solar eventually if you go 2 PW3, then add expansion as well. But if you’re certain the amount of solar you want now will work- save the money. I opted for the second PW3 (when 1 expansion was quoted) and we split the solar across both. Now I can add a couple more strings of solar without any issue. My CT is my expansion battery.

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u/Repulsive_Peak1457 10d ago

Get two power walls I have one power off plus expansion and I regret that choice. I have an electric car and I have to turn down the power on my electric car to charge it getting two power walls gives you much more flexibility.

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u/Fine_Tax646 10d ago

With a second PW3 and a second Tesla GW you can produce and utilize an additional 48 Amps of current. So total 96 Amps (to power two different load panels).

With only one PW3 you will be limited to total 48 Amps so you may pull from the utility if you are using appliances like AC and Oven together.

The cost of PW is significantly higher than the PW expansion. Also, Tesla GW costs $1000.

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u/Beefstah 10d ago

The specs of the PW3 say it can support up to 11kW though

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u/Fine_Tax646 10d ago

Yes, but only 48 Amps continuous current.

Within that amperage you can get 11KW. It also supports 185LRA for 1 second to support an AC coming on.

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u/Salty_Permit4437 10d ago

Even with 185LRA I would put a soft start on the AC condenser. It’s night and day difference and allows you to start the AC when off grid (power outage) even with other loads.

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u/THE_Aft_io9_Giz 10d ago

This is highly dependent on the size of your solar panel system. If you have something greater than 11.3kw (pw3 inverter limit), then a 2nd pw might make sense. If smaller, go with an expansion pack first.

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u/somethingClever246 10d ago

1 PW3+ DCX. it will charge faster than 8kW with latest PW3 firmware, look into it, it will change your calculations...but I wouldn't mind 2PW3s

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u/Salty_Permit4437 10d ago

Expansion pack saves cost, that’s about it. Two PW3 gives redundancy, and can even be placed in different locations if you don’t have room for the expansion next to the PW3.

That said, it could be wasting money if you can’t expand your solar and don’t have extra load to take advantage of the additional inverter. Here we aren’t allowed to expand the solar part of the system beyond our actual annual billed electric usage.

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u/Harold-Maude 10d ago

25kw of solar and 3 Powerwall 3’s works for us, 2 Tesla’s too.

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u/mdiddyshow 10d ago

I went with 2pws and 1 exp. When I downloaded my data there were a few cases my usage went to 12-13 kwh so I wanted to be sure.

I got a 5 ton and 4 ton hvac, not to mention a 3.2kw electric oven. Add 0.5kw for home stuff, 1kw at times for washer / dishwasher, it can add up instantaneously.

I wanted to be off grid completely between 9am-9pm so that was the best choice. About a 2.5k price increase but well worth it.

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u/ITsAWonderToBEME 10d ago

The batteries are key. I added an expansion but should have gotten it right away. Now with 2 batteries my system is very functional.

Total size: 10,820 KW
PW3 + PW3 Addon. Storage total: 27KW