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NOOB Powerwall Question(s)?

RubberToe

Supporting the greater good
Jun 28, 2012
2,981
7,095
El Lay
All,
Long time TMC member but this is the first time I have ever ventured into the Tesla Energy thread. Been reading about the horror stories coming out of Texas due to the lack of power. I checked the Tesla website and the Powerwall FAQ states that a single Powerwall will only support the following loads, and note that A/C is not on the included list:

PW Loads.jpg


The home where we would possibly be installing this is a bit of a special case. When we installed our SPV array back in 2016, we sized it to be more than 2x the amount of power we would use on average. With our current SCE power plan, we are fully net metered, our monthly bill is $12, and once a year we get a check for $60 from SCE during our "true up". So the Powerwall wouldn't provide any benefit from a cost savings standpoint given the net metering situation, it would only be required in case of power loss.

My question is basically, can the Powerwall also support our A/C unit should there be a power outage during the hottest summer months? Not sure if the loads supported by the Powerwall are only on specific dedicated circuits, or whether the Powerwall feeds the entire house, and you need to scale back the consumption manually. I suspect the former.

The reason I think that the A/C might be able to be included is that the total power draw might not be that large, but it may be an issue of instantaneous draw. Not sure what the tonnage of the A/C unit is but I can find that out if needed. The home is 2 miles from the ocean in Southern California, and is only 1,100 square feet. The A/C is typically only used about 10 days per year due to the ocean breeze keeping things relatively cool even in summer. See below for the home energy usage from the hottest month of 2020.

I suspect that we will get the Powerwall in any case, just wondering about the A/C question since an elderly family member resides in the home currently. Having the A/C available during an outage would be icing on the cake.

August SCE.jpg
 
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dortor4ev

Member
Feb 24, 2013
209
331
San Jose, CA
it all depends on the “type” of AC compressor you have an your startup load - you’d need at least 2 and probably 3 - only Tesla’s design team can answer that - and you’re unlikley to get their attention any time soon - I have neighbors that have been waiting for their powerwalls since lack june…

generators are cheaper, but noisy and ultimately need to be fueled - powerwalls should run indefinately if it’s sunny the next day - I would order a two wall system and be prepared to bump it to 3 when it comes time to finalize the system design - ultimately you’ll be happy with them - we love our - and they have bridged no less than 60+ (total 48 hours) outages for us in the past 2 year of install - my wife loves them - last outgage about a month ago was 17.5 hours.

yes you ahve to shed load manually when you are on battery power, but I’ve got some homekit automations that take care of some of that.

good luck
 
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jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,237
9,095
Riverside Co. CA
All,
Long time TMC member but this is the first time I have ever ventured into the Tesla Energy thread. Been reading about the horror stories coming out of Texas due to the lack of power. I checked the Tesla website and the Powerwall FAQ states that a single Powerwall will only support the following loads, and note that A/C is not on the included list:

View attachment 638274

The home where we would possibly be installing this is a bit of a special case. When we installed our SPV array back in 2016, we sized it to be more than 2x the amount of power we would use on average. With our current SCE power plan, we are fully net metered, our monthly bill is $12, and once a year we get a check for $60 from SCE during our "true up". So the Powerwall wouldn't provide any benefit from a cost savings standpoint given the net metering situation, it would only be required in case of power loss.

My question is basically, can the Powerwall also support our A/C unit should there be a power outage during the hottest summer months? Not sure if the loads supported by the Powerwall are only on specific dedicated circuits, or whether the Powerwall feeds the entire house, and you need to scale back the consumption manually. I suspect the former.

The reason I think that the A/C might be able to be included is that the total power draw might not be that large, but it may be an issue of instantaneous draw. Not sure what the tonnage of the A/C unit is but I can find that out if needed. The home is 2 miles from the ocean in Southern California, and is only 1,100 square feet. The A/C is typically only used about 10 days per year due to the ocean breeze keeping things relatively cool even in summer. See below for the home energy usage from the hottest month of 2020.

I suspect that we will get the Powerwall in any case, just wondering about the A/C question since an elderly family member resides in the home currently. Having the A/C available during an outage would be icing on the cake.

View attachment 638276

No, one powerwall generally wont support AC. 1 powerwall will not be able to support anything more than 30amp breaker, and I have never seen any reported install with 1 powerwall with an AC backed up (usually due to the startup load issue you talked about)

And no, it does not "take 3 powerwalls" for every install with A/C as is insinuated by another poster in this thread. I have (2) A/C units backed up by 2 powerwalls, and posted pictures of my install panel to prove it. How long you could run it would be a different thing, but in your case, OP, you state you live by the coast so how long you could run it wouldnt be much of an issue. In your case, it wouldnt make a ton of sense to back up the AC unit in the first place. I would exclude that load.

As for your other question, whether the powerwall(s) are setup to backup your whole home or specific loads depends on your home loads and how many you buy. 1 powerwall is almost always "specific loads", and since 1 only supports up to 30amps, would not support most wall ovens, A/Cs or other large loads.

Since it sounds like you are under NEM1, adding powerwalls will not (currently at least) change your net metering, even though it will require another submittal for PTO. You also wont need to change your current plan if you dont want to. That means, as you surmise, there is no real payback aspect for the powerwall in your case (just like a generator).

TL; DR , No, 1 powerwall will not likely cover any A/C unit that I am aware of, No, it doesnt take 3 powerwalls to cover every A/C unit, and in a 1 powerwall install, it is "essential loads" that are backed up.
 

dortor4ev

Member
Feb 24, 2013
209
331
San Jose, CA
the other poster insuniated “2 or 3” - probably 3 if your AC loads are high enough - where mine ARE for my install - I required 3 powerwalls - so it all depends on your circumstance, jsut because you have weak ass wimpy AC system doesn’t mean the rest of us are installing such low end crap.
 

ucmndd

Well-Known Member
Mar 10, 2016
6,413
11,962
California
the other poster insuniated “2 or 3” - probably 3 if your AC loads are high enough - where mine ARE for my install - I required 3 powerwalls - so it all depends on your circumstance, jsut because you have weak ass wimpy AC system doesn’t mean the rest of us are installing such low end crap.
What a weird, fragile ego you must have for “manly air conditioning” to be a source of pride.

What’s with the ‘tude?
 

BGbreeder

Member
Jun 19, 2020
182
100
Bay Area
The devil is in the details of what the startup draw is on your AC. Look for an entry on your AC nameplate for LRA (Locked Rotor Amperage). The max for a single Powerwall is 29A for ten seconds, and the maximum sustained draw is a bit over 20Amps. There are ways to mitigate this, but at the end of the day a Powerwall only stores 13.4kWh of energy, and air conditioning units can burn through that pretty quickly.

If the goal is keeping an elderly relative cool, you might consider a small portable unit to locally cool your relative. Of course, if you can avoid the AC entirely, your Powerwall will keep things running longer.

With a single Powerwall, most (all?) owners have a subset of their circuits backed up. The logic being that the Powerwall won't instantly kick off due to overload when the grid drops. Even with more Powerwalls, it isn't a bad strategy to reduce the the total load.

All the best,

BG
 

miimura

Well-Known Member
Aug 21, 2013
6,176
5,774
Los Altos, CA
Each Powerwall can only back up a load with a breaker of 30A per Powerwall. The LRA rating of the A/C compressor is also important. I'm not sure of the exact value, but 40 LRA per Powerwall would probably work. For example, an A/C unit with a 40A breaker and 120 LRA would probably require 3 Powerwalls to work when the grid is down. A mini-split with a 20A breaker and 24 LRA could be operated on one Powerwall.
 

Laketime

Member
Dec 13, 2020
132
74
LI NY
I would look to do 2 walls, one will certainly not be enough. Judging by your location and house size you probably have a 2 ton AC unit (just a guess though). What really matters is the startup and efficiency of the AC unit though. A 2 stage unit will have a much lower startup load and continuous one as well. And since most of your use would be during the day when it is hotter you would be supplemented by your solar. Keep in mind all of the tax incentives when looking at price.

the other poster insuniated “2 or 3” - probably 3 if your AC loads are high enough - where mine ARE for my install - I required 3 powerwalls - so it all depends on your circumstance, jsut because you have weak ass wimpy AC system doesn’t mean the rest of us are installing such low end crap.
What a rambling incoherent statement without clear direction of who you meant it for. Grow up.
 

Laketime

Member
Dec 13, 2020
132
74
LI NY
Seems from all I read you would need 3. Generator would be much cheaper.
It really depends on locations. When I did my 3 walls last fall it was much cheaper than a WH generator because of package discounts and fed/utility incentives. It would up coming to roughly $8600 for 3 walls installed vs $12,500 for a WH gen plus the annual maintenance and fuel cost.
 
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h2ofun

Active Member
Aug 11, 2020
2,217
343
auburn, ca
the other poster insuniated “2 or 3” - probably 3 if your AC loads are high enough - where mine ARE for my install - I required 3 powerwalls - so it all depends on your circumstance, jsut because you have weak ass wimpy AC system doesn’t mean the rest of us are installing such low end crap.
I just love the comments that it might "work" on 2 but how long you can run is a different story.

With my generator and fuel source, I can run them as long as I want.

Each solution has pro and cons. I just see too many thinking batteries will let them pretend there is no power outage.
 

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