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Powerwall 2 and Central Air question

Discussion in 'Tesla Energy' started by jurmanji, Aug 14, 2018.

  1. jurmanji

    jurmanji New Member

    Joined:
    Aug 14, 2018
    Messages:
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    Location:
    LA
    Am putting in an 7.15KW system and was thinking about doing 2 powerwalls. Would that power the central AC 3-31/2 ton (Trane XL14i) overnight? I'd love to stop paying the power company all together. In LA and since we are central it stays hot at night.

    Had read somewhere that a single phase soft starter could be helpful.

    Love any thoughts and help!

    Thanks!
     
  2. arnolddeleon

    arnolddeleon Supporting Member

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    Location:
    California
    The short answer is likely no. A better answer is going to require more information and time.
     
  3. rp2112

    rp2112 New Member

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    Aug 14, 2018
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    Location:
    Irvine, CA
    A soft starter will nearly be a must, as even my rinky-dink A/C used to draw more than 90 Amps during start (with the soft-start, it draws about 24 or so). You'd be close to the current limit, even with two PowerWalls. Tesla will install the soft starter for you, included with everything else.

    With two PowerWalls, you'd have 27 kWh maximum (if they're both fully charged when you start running your A/C in the evening). My 3-ton A/C draws 2.6 kW when it runs, and my house takes about 0.3 kW to keep things running at night, so, 2.9 kWh for an hour. So if I ran it for 9.5 hours continuously, I'd completely drain both fully-charged Powerwalls.

    However, of course, the A/C does not stay on continuously. And, I've set up my Nest to keep things comfortable during the night-- start out at a higher temperature, but drop the temp every couple of hours. That way the A/C runs more efficiently as the ambient temp cools down further at night. So, it doesn't have to run as long each cycle, but it keeps the rooms at a nice temperature. So, let's say I run the A/C a total of about 6 hours at night (4 cycles, 1.5 hours each cycle). That would put total power consumed at 17.4 kWh. You can use that as a point of reference. It'll depend on how drained your PowerWalls are when the panels are no longer producing, how much other power your house draws during the night, and how many total hours you run the A/C at night.

    From early March to the second week of July, I was 100% running on only solar and one PowerWall, so I'm rooting for you. I imagine I'll return to that in Fall, and most of Winter.

    Best Wishes!
     
  4. Brovane

    Brovane Member

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    Sep 7, 2016
    Messages:
    178
    Location:
    Orange County, CA
    I would assume your power company is LADWP?

    I have a 5-ton Trane unit and it uses about 25-30 kwhr a day during the summer to keep my house cooled down. I live around the Irvine area of CA.

    I have 2 PWs and using my AC from 2pm-8pm and regular house draw will drain my batteries down to about 30-35% from 100% during those 6-hours. No way would they last all night.

    For SCE the peak time is 2pm-8pm so my house is powered on batteries alone and all solar generation goes back to the grid to maximise by return.
     
  5. llngoc

    llngoc Member

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    Location:
    Bay Area
    If you are not planning to use the AC off-grid/backup, is the soft started necessary? I was told that during peak hour, the PW2 will be discharging to meet all needs in the house for as long as possible including the AC. In fact, my AC is on the other side of the backup gateway so when the grid goes down, I will not have AC anyway.

    Cannot test our my assumption yet as I don't have PTO from PG&E yet.

     
  6. cwied

    cwied Member

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    382
    Location:
    San Mateo, CA
    As you suspected, the extra current should come from the grid if the grid is still connected. I haven't tested this exact scenario, but I have pulled more than 10 kW, and there is no issue doing that. 10 kW come from the Powerwalls and the rest comes from the grid.
     
  7. llngoc

    llngoc Member

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    Location:
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    That's exactly what I thought.

     
  8. miimura

    miimura Active Member

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    Aug 21, 2013
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    3,078
    Location:
    Los Altos, CA
    Also, if you're not going to install soft start and you're not going to run it during an outage, you should have it wired outside the gateway. Then the whole soft start thing is a non-issue.
     

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