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APS customer with solar, plan question

Discussion in 'Tesla Energy' started by destructure00, Sep 22, 2019.

  1. destructure00

    destructure00 Active Member

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    I'm in Phoenix as an APS customer, working on having the 11.4kw system designed and installed on my house. One of the documents I had to sign was a recommendation for rate plan change to the Saver Choice plan that has higher on and off peak rates as well as a grid access charge, but removes the "unpredictable" demand charge.

    I'm currently on the Saver Choice Max plan. Until yesterday I hadn't taken the time to understand what a demand charge was, but after reading up I'm fairly confident that I can manage on-peak demand (with or without solar) to reduce the demand charge as much as possible.

    Question then, as long as I can manage the on-peak demand, is there any other reason to change plans?

    Here's what I have (Saver Choice Max):
    On-peak: .08683 summer / .0656 winter per kwh
    Off-peak: .0523 per kwh
    Super off-peak: N/A
    Grid access charge: N/A
    Demand charge: 17.438 summer / 12.239 winter per kw

    Here's what Tesla recommends (Saver Choice):
    On-peak: .24314 summer / .23068 winter per kwh
    Off-peak: .10873 per kwh
    Super off-peak: .03200 winter per kwh
    Grid access charge: .93 per kw-dc
    Demand charge: N/A

    Peak time is 3pm-8pm M-F. The daily basic service charge (.427) and excess production buy rates (.1161) appear to be the same regardless of which plan I'm on, so I left them out. Also, FWIW, about 85-90% of my usage is currently off-peak. My demand charge last month was based on 9.2kw (had A/C and pool pump on at the same time one afternoon), but I'm making some changes here that should prevent this in the future.

    Between the higher rates and grid access charge, the recommended plan actually seems much worse to me. What am I missing? Do they just make the assumption that people can't effectively manage the demand charge?
     
    • Informative x 1
  2. jeep1979

    jeep1979 Member

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    When I was having Tesla install my 2 Powerwalls, one of the documents they sent me to sign was to switch me from an annual billing plan to a monthly one. This meant that in the winter time when my usage was greater than my solar production, I would have to pay. When I called up to complain about this, Tesla said that wasn't required and I didn't have to sign and agree to that change. So it seems there may be some flexibility in these things.
     
  3. destructure00

    destructure00 Active Member

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    Yeah the letter words it as a recommendation, just wondering what the best choice is.
     
  4. animorph

    animorph Active Member

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    Can't help with the solar part, but I'm on Saver Choice Max as well. We have a load controller, but it's only controlling two heat pumps out of three. No way I'd change rates. I thought solar generation would be a great match to the peak period. Especially if a Powerwall could pick up the slack until 8 PM.

    I can certainly see the demand charge being tricky if you ramp up your demand to match the solar output and then a big storm comes through and you have to cut your total demand to avoid a large demand charge. A load controller watching only the grid usage would be able to shed some of your demand automatically in that case, while letting solar supply a higher demand when sunny. You might have to be a little more active in managing your grid demand without a load controller.
     
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  5. nwdiver

    nwdiver Well-Known Member

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    The demand fees only apply during peak hours?
     
  6. destructure00

    destructure00 Active Member

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    Correct
     
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  7. destructure00

    destructure00 Active Member

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    My three biggest consumers are A/C, pool pump, and charging my car. Charging starts at midnight, pool pump cuts off at 2pm, so the only thing left is A/C. I'm going to start precooling the house with the goal of having no A/C usage between 3 and 8pm. Then all that's left to watch then is clothes dryer, oven, cooktop, etc...and we are in direct control of those things.
     
  8. brur

    brur Member

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    #8 brur, Sep 22, 2019
    Last edited: Sep 22, 2019
    I didn't notice if you are going to use batteries. If you are, stop reading this.
    I can't imagen living in the valley and not using AC in the peak hours. If I remember correctly one of the plans have you paying more for typical non-peak and something a little more for peak. And another plan that is low off-peak and expensive on peak. In your case, that is what I would avoid.

    Do you think you will have excess capacity? I doubt that you will. I charge the car (15k miles a year) a bit more than once a week, 18 panels, new home, and paid about $10 last month. As you know the typical day here is 17 or more degrees cooler than Phoenix.

    between 3 and 8 it's going to get pretty warm. I suppose if no one is home you could pre-chill to about 58.

    As an exercise, I treated myself to the notion I was paying dearly for peak, tried chilling the house a few degrees but that doesn't last long enough, and sometimes I'm home or have friends over so super chill isn't in the cards.
    At any rate, I am of the notion you can change your billing style afterwards.
     
  9. brur

    brur Member

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    It's almost cool season there now. So you could do one method winter and another summer.
     
  10. destructure00

    destructure00 Active Member

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    No batteries. I'm not sure about the excess capacity, it's a 36 panel 11.4kw system but the way it's split on my roof (half east and half west) I'm guessing I won't see anywhere near the full capacity.

    I have a Hubitat smart home hub that manages my thermostat, so I can see history. Back on a 110 degree day it took about 2 hours for the indoor temp to rise from 76 to 80 after the thermostat shut off. I was going to start by precooling to 70 and see how fast the temp rises after that. Ideally I'd like it to stay at or under 80 degrees during the peak period. I have the precool start time dependent on outdoor temperature. All of this will be tweaked as I learn more I'm sure, and I'd like to eventually tie in either an outdoor lux component or if I can, even get the solar production data sent to Hubitat. This way, if the panels are producing enough, I can continue to run the A/C during peak periods, but then have it shut off if it gets cloudy or whatever. I'm sure it'll be a learning experience.

    True. As posted above, I'd really like to get the solar production data and outdoor temps dialed into the precool strategy, then it becomes season-independent.
     
  11. brur

    brur Member

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    Just guessing here, seems like APS would charge you the peak price during peak, even if you were producing power during that time. Then they would pay you back at the lower rate, a net loss, but still might be a good idea.

    What you are doing sounds interesting. The whole exercise is so obscure to me. The variables. the regulations, the options. You are adding to the knowledge base.
     
  12. PHX3

    PHX3 Member

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    I just had a 12.1kw non-Tesla system installed in APS territory last week. I've been on Saver Choice Plus for a while now. Tesla also made the recommendation to switch to Saver Choice when I was working the process with them. I think in most places in the country a flat rate plan makes sense.

    For us with APS and solar I agree that the Saver Choice plan is not a good idea.

    APS actually recently sent me a letter saying I could save a little by switching to Saver Choice Max. When I ran the numbers prior to this summer it included last summer which had high demand (>9kw). This past summer was closer to 7kw. I guess the higher demand charges of the Max scare me a little. My current strategy is to stick with Plus for a year so I can compare apples to apples and get actual data for solar production and see how that offsets my usage during demand timing.
     
    • Informative x 1
  13. destructure00

    destructure00 Active Member

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    I'm under the impression that I get to use whatever I produce first, and any excess gets sold back to APS.

    Thanks for the info, kinda confirms what I'm thinking as well. I still feel like as long as I can control the on-peak demand charge I should be fine, just wasn't sure if I was missing something.
     
  14. destructure00

    destructure00 Active Member

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    Here's a visual of what I'm trying to avoid. Last Friday we had the A/C running because we were home in the afternoon during on-peak, wife was doing laundry. I had the pool pump running until 3pm too. High on-peak demand of 8kw or so.

    Screenshot_20190924-061349.png

    Yesterday was the new strategy where A/C doesn't run during the peak period, and didn't have laundry or anything else running. Also changed the pool pump to shut off at 2 instead of 3. Weather here was wacky so no need to precool the house, but this is the goal:

    Screenshot_20190924-061402.png

    The difference of 6kw peak demand would result in a savings of $105 or so if I could keep it up for the entire month...at least that's my current understanding.
     
  15. destructure00

    destructure00 Active Member

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    Pretty obvious when my car is charging :D

    Screenshot_20190924-062545.png
     
  16. Chancellor32

    Chancellor32 Member

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    So to give you an idea on the demand vs no demand route. SRP has the E27 plan with rates being $.03-$.06 and demand charges starting at like $8. Since getting solar and 1PW I dont use the Grid at all during the 2-8pm window because my 4.1kw system and PW can handle our usage. It has been a game changer, highest demand charge has been .8kw or $6. I would suggest if you are getting a demand plan to look into getting the Powerwall. APS has a crazy high sell back but you can plan on solar dying at like 5-6pm and you still have a few hours before peak is over. One AC kick and boom you get a 4-6kw demand charge on top of your other charges.
     
    • Informative x 1
  17. destructure00

    destructure00 Active Member

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    Tesla threw a wrench in my plans this afternoon, told me I need a main panel replacement for $2700. I already have a 200 amp panel, which is fine. Apparently the problem is the fault current of the breakers? They are all 10kA, where according to my Tesla rep APS requires 22kA breakers. The main 200 amp breaker apparently is not available in a 22kA variety.

    I contacted a 3rd party electrician who does engineering design for solar systems and he's never heard of any requirement for a city or utility in AZ for a fault current over 10kA. I found the APS interconnect requirements online and couldn't find any references to this either. Emailed the rep back and asked her to point me to where APS specifies the 22kA requirement, so I guess we'll see what happens there. Not sure I'm up for $2700 out of pocket right now.
     
  18. destructure00

    destructure00 Active Member

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    Thanks for this, I'd love to do a PW in the future for sure.
     
  19. PHX3

    PHX3 Member

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    I ran the numbers with a large array and no battery against a smaller array with battery and large array with no battery came out ahead. Batteries are still very expensive and you need to figure in that they'll only last 10yrs. I'd love to have batteries but by the time the savings pays back the cost of the batteries it will be time to replace them.

    I believe the differences that make batteries work in SRP territory but not APS is that SRP won't pay you very much for excess generation and SRP offers a large rebate on batteries due to their settlement with Tesla.

    For APS you're only locked in to the 11.6c buy back rate for 10yrs. I hope by that time the price of batteries will decrease to the point that adding a battery at year 10 makes sense.

    I had 200A service and needed to get de-rated to 175A. Kind of surprised you don't need to, unless maybe they're using the smaller 10kw SolarEdge inverter and its just under the threshold. I did not experience anything on 10kA vs 22kA, sure hope it doesn't come up during the final PTO evaluation!
     
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  20. vickh

    vickh Active Member

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    does APS limit switching? I'm getting an error here; Error

    Error
    An unexpected error has occurred.

    Go back to site
     

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