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Thinking about going solar for my business, totally new at this.

Discussion in 'Tesla Energy' started by JMG, Aug 22, 2016.

  1. JMG

    JMG Member

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    Location:
    NE Texas
    Model S Owner here. Looking for advice/tips.

    I have two offices that I am thinking about putting solar on. I have some money sitting in a CD that is obviously earning nothing, so I thought why not use that to invest in something with a guaranteed rate of return.

    Both offices have flat metal roofs. Main office is a bigger building. Average monthly kwh usage is 1,000 kwh. Average monthly bill is $200-$210.

    I emailed 4 solar companies for quotes, but only one responded. Here is his quote for my main office only, I haven't requested quotes for my branch office yet. He gave me two options:

    System Details:
    System Size STC Rating 8.55 kw
    DC Annual AC Solar Production 10,934 kwh
    Average AC Monthly Solar Production 911 kwh
    Your Average Electrical Consumption 1,100 kwh
    Energy offset in % 82% coverage
    Solar System to be mounted on: Roof Mount System
    30 Solarworld 285w American made Or LG 25 year warranty

    Option #1

    SolarEdge & 30 DC optimizers
    Gross System Investment $ 25,505.78
    Oncor Incentive (estimates) $ 5,557.50
    Your Investment minus Oncor cash Incentive $ 19,949.29
    USDA grant (eligible, but guarantee) $ 6,376.45
    Federal Rebate at 30% $ 4,071.55
    Net System Investment $ 9,500.29
    System Cost per watt $ 1.11
    Payoff period at today’s rate 7.8 yrs
    Solar Module Warranty (80% production) 25 yrs
    Inverter Warranty 12 yrs
    DC Optimizers 25 yrs
    System Monitor of Production yes

    Other option:

    30 AC Micro Inverters
    Gross System Investment $ 28,020.68
    Oncor Incentive (estimates) $ 5,557.50
    Your Investment minus Oncor cash Incentive $ 22,463.18
    USDA grant (eligible, but guarantee) $ 7,005.17
    Federal Rebate at 30% $ 4,637.40
    Net System Investment $ 10,820.61
    System Cost per watt $ 1.27
    Payoff period at today’s rate 9 yrs
    Solar Module Warranty (80% production) 25 yrs
    Inverter Warranty 25 yrs
    System Monitor of Production yes

    So I guess my questions are:
    • Do these quotes look accurate?
    • No idea if the 2nd quote is "better" than the first due to the added costs? Just the warranty?
    • Should I go ahead and sign up now and get on the waitlist for 2016 funds, or do I risk them being exhaused? Or should I wait until 2017?
    • Should I keep calling until I get a 2nd quote?
    • Or should I just wait until the Tesla/Solar City merger happens and see what they have to offer? Right now SolarCity doesn't offer anything in my zipcode.
    Thanks!!!
     
  2. bonaire

    bonaire Active Member

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    #2 bonaire, Sep 6, 2016
    Last edited: Sep 6, 2016
    Business electricity rate there is .20/kWh all fees included? That is quite high, for Texas. Isn't there a lot of wind resources there that have some folks actually going negative at night for their power pricing?

    At .20/kWh, sure it makes sense to supplement with Solar.

    That Oncor delta and USDA grant seems juicy as additional benefits. Enormous. What about a very simple string inverter setup? Your sizing is so much like my own home configuration. I ended up with two PowerOne Aurora (now ABB) 3.6 inverters along with 8.1 kW of SolarWorld modules. Modules and inverters, both American made (which I wanted). You probably would go with 4.8 inverters and up to 8.55kW. If you can go larger, consider 9.2kW and 4.2 inverters and would cover your whole kWh demand. That would be quite inexpensive and if kept clean, you have no reason to use all sorts of complexity with the microinverters. Each Aurora has two MPPT in them, making 8.1 kW of my system have four inverters. I review their output at high-sun about twice a month and both strings match after 4 years. To the watt if I do a cleaning on them earlier in the day and they produce more power than we calculated up front, about 12MWh a year in the northeast. If you have no trees or shading issues with rooftop pipes, etc. - then individual inverters on each module is not that useful.

    With those incentives, you just want to pick the cheapest installer who can do a good job. No reason to expect SolarCity to come and match a low-cost installer. Some have written that costs of a purchased system through SC is slightly more than independents. Get three quotes and choose wisely. But an $11k out of pocket investment is going to pay off well. saving almost the entire bill monthly, five year ROI is expected. Everyone should be doing that in your area.

    That is, if your kWh pricing is really .20+/kWh as you say. And while researching, consider conservation efforts in the office space as well. Conserve-first, then add renewables. $1 conservation is worth $4 in renewable equipment (used to be $5). ROI on LED lighting to replace halogen or other incandescent lights pays off fast.
     
  3. bonaire

    bonaire Active Member

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  4. Alketi

    Alketi Member

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    Welcome! I'll offer a few rules of thumb:

    First, the number to compare quotes is $/Watt, before incentives.

    Your quotes are $2.98/W and $3.27/W respectively. Installers will try to hide these numbers with other incentives and such, but look at the raw totals.

    I suspect both are fairly decent, at least they're cheaper than my install in MA, but you should get other opinions.

    Another rule of thumb is that microinverters are more of a benefit for shady installations. If your roof is baked in sunlight, without tree cover, then microinverters will be of less benefit.

    Some websites:

    Google Project Sunroof (Put in your address. May not work in your area or for businesses)
    Project Sunroof

    Forum for solar panel questions (to compare prices for your area)
    Solar Panels for your Home, Grid Tied Solar PV - Solar Panels - Solar Panels Forum

    Calculate yearly output (They're likely using this to predict monthly/yearly output. You can too)
    PVWatts Calculator
     
  5. bonaire

    bonaire Active Member

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    #5 bonaire, Sep 7, 2016
    Last edited: Sep 7, 2016
    With your power bill - does that include a time of use pricing plan? Why not consider a battery or two that simply charge at night and dump during the daytime in order to slow your peak demand period. They might be treatable to the 30% ITC, if not other incentives. If you could charge at night with texas wind in the sub .05/kWh rate, you could bank a bunch of power and output it during the day. Solar installers may have done some of this in your area. It wouldn't be as costly as a solar install and still offer good ROI. But most likely too is a power review of the business and conservation efforts as a very first step. Are there ways to cut 10% of power demand without anything other than power planning changes? Then lighting and AC cycle reviews, refrigerator coils need cleaning? Anything else? Lots of ways to cut the power demand. If you expect to have an EV at the business and recharge mid-day during the business day, then Solar PV is really the right way to go.
     
  6. glenhurst

    glenhurst Member

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    Why are microinverters more of a benefit for shady installations?
     
  7. Alketi

    Alketi Member

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    Microinverters convert each panel to AC, directly at the panel, so if a few panels are in the shade, then they don't affect the entire system. The cheaper way to do it is to string all the panels to a centralized inverter (one you need to put somewhere) and convert them all to AC at once. In this case, "optimizers" are used on a per-panel basis and somewhat mimic the microinverter's ability to isolate panels.

    The other issues are 30 failure points (for microinverters) vs one failure point for a string inverter. And, that the microinverter approach is generally more expensive. The microinverters also remove the need to house a large inverter somewhere on your property.

    Tesla, I believe, will ultimately use a string inverter in their integrated PowerWall setup, not microinverters.

    Personally, I have microinverters built in to SunPower 250AC panels, as my roof has some shade at certain times of the day.

    This site explains the differences fairly well. Comparing Solar Technologies, Inverters | EnergySage
     
  8. mspohr

    mspohr Active Member

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    If you have partial shade on a few panels, the string inverters will drop the output of the whole string. Microinverters on each panel will only drop the output for the shaded panels. If you have trees and partial shade during the day, microinverters are best, otherwise, the string inverter will cost less and give the same output.
    Look at the cost per watt before incentives. Your prices look good. Prices have been $4-$5 /watt and have been dropping. DIY you could get it down to $2/watt but there is more risk and more work.
     
  9. Saghost

    Saghost Active Member

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    Since the other offering was a Solar Edge Optimizer system, it has a failure point at each panel, too - the optimizer is a solid state dc-dc converter and certainly subject to failure and will drop the panel out of the system if it fails.

    An important point I didn't get out of your summary is that the microinverters are all in parallel. Yes, 30 chances to fail, but the failure of one will have a minimal impact on the overall performance - that panel will stop contributing, but it has no effect on the other 29.

    I would think microinverter failures are also less likely, because there's a lot less heat involved and lower voltages. Certainly the longer warranties on microinverters would support this (though it could also be the company trying to reassure people - Hyundais with 10 year warranties aren't more reliable than Hondas with 3 year ones.)

    A conventional string system isn't as safe as the microinverters, but the Solar Edge is close - it still has 400V DC floating around (like the string, unlike microinverters,) but only when the inverter tells the optimizers it is okay.
     
  10. mspohr

    mspohr Active Member

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    I hadn't noticed before but your "string" option is actually DC optimizers at each panel which does compensate for partial shade on the string but also gives you failure points at each panel.
    If you have full sun, you might want to look at a standard string and large inverter setup which would be less expensive.
     
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  11. Garlan Garner

    Garlan Garner Active Member

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    I've never had an optimizer fail - in 4 years.

    You can track my progress for each panel for the last for years by clicking on my signature. Optimizers are tremendously more reliable because they are DC-DC converters.....not DC-AC like micro inverters. I used to have micro inverters from Enphase however I had to get rid of them because I had 4 to go bad in 6 months. They are really difficult to replace when the ones in the middle go bad.

    My son and I installed our system.
     
  12. nwdiver

    nwdiver Active Member

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    Microinverters are subjected to MORE heat. Unless you find a way to install them not on the roof under the array the ambient temperature under the panels regularly reaches ~70C. Even the hottest of garages rarely reach 40C. The 25 year warranty exists more out of necessity than longevity. If an inverter is mounted with a panel its warranty kinda has to match the panel. ~20+ year warranties are available for string inverters also.

    Optimizers are much more robust since they only handle the MPPT function and not the DC-AC.

    Unless you have complex shading issues or different angles it's far more cost effective to use a simple string inverter undersized by ~20%. String inverters run $0.30/w. Solaredge ~$0.40/w and micros ~$0.60/w.
     
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  13. Garlan Garner

    Garlan Garner Active Member

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    #13 Garlan Garner, Sep 7, 2016
    Last edited: Sep 7, 2016
    Whoa.

    I've installed both - myself on my own home. Thee is no where to install microinverters or optimizers except behind the panels.

    Microinverters = DC-AC. Installed behind the panels. Voltage = 12-34VDC to 120AC MPPT - YES Price = $120 per
    Optimizers = DC-DC. Installed behind the panels. Voltage = 12-23VDC to 450VDC. MPPT - YES Price = $75 per

    Microinverters = Very difficlut to install batteries because the voltage leaves the panels at 120VAC
    Optimizers = Very easy to install batteries because its DC all the way to the inverter.

    Microinverters = Requires significant lightning arrestors and such because AC is covering your roof.
    Optimizers = Simple grounding required.

    Microinverters = Lots of regulations and permits required due to AC being installed external to the house.
    Optimizers = Simple DC entering the house ( much safer ).

    Microinverters = Requires a circuit breaker on your main panel.
    Optimizers = Can actually be plugged into an outlet as long as each inverter gets plugged in to each side of your panel. ( if you have more than one inverter....as I do. )

    I wouldn't even consider string inverters. Its just not smart anymore. Anywhoo. Below is a sample using the Tesla Powerwall, however I'm using different batteries. I have some AGM batteries.

    StorEdge%20Flyer_Grid-tied%20and%20Backup_NA_letter_3.png

    watch my solar progress here. SolarEdge
     
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  14. nwdiver

    nwdiver Active Member

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    Technically Solaredge IS a string inverter.

    I agree that DC optimizers are better but the math generally doesn't pencil unless you need multiple MPP trackers. A solar edge system will run ~$0.15/w more than a standard string inverter. For a 8kW system that's another $1200. I can get panels for $0.62/w... unless you're space constrained and need to squeeze every watt you can out of every sq ft you're going to get more bang for your buck buying another 2 kW of panels.

    When I design a system I'm going for the lowest $/kWh possible. I don't skimp on the inverter... Fronius and SMA are top-notch brands too and it's far more likely than not that they'll keep operating for 20+ years. Panel failures are exceedingly rare. I've installed ~100kW and I've only seen 2 bad panels... both were manufacturing defects.

    Totally agree that Solaredge + Optimizers are the best solution. But for most of my projects I have to be more cost conscious. PLUS I typically oversize my arrays by 20-30% so the efficiency gain with optimizers would be lost for most of the day anyway.

    More storage solution are coming soon...

    [​IMG]
     
  15. mspohr

    mspohr Active Member

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    I understand string inverters (string 30+v panels in series to get about 300vdc and run that through an inverter to get 240vac split phase.
    I understand microinverters (30+v input from one panel and 240vac output)
    I don't understand "optimizers" (DC to DC string). How do they handle DC-DC? The only way I know to do that is to go DC-AC-DC. Do they do something else? It seems that optimizers have the disadvantages (cost, complexity) of microinverters plus the disadvantage of string (large inverter subject to failure).
    Could someone explain how an "optimizer" works? I've spent a lot of time on the Solar Edge website and never got a clear answer.
    (Note: I'm an EE so do have some understanding of the basics.)
     
  16. nwdiver

    nwdiver Active Member

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    I kinda press the 'magic' button on that one ;)

    I can explain WHAT they do... but not HOW they do it.

    It's kinda genius actually... in a panel string the current goes in and goes out MUST be equal. This is Kirchhoffs current law. The Max Power Point is based on light and will be slightly different for each panel. In a typical string the MPPT is 'averaged' leading to losses that can be as high as ~15%.

    An 'optimized' string takes the MPPT point of each panel. The optimizers somehow talk to each other so that the string voltage is ALWAYS ~350v. 9-26 panels I believe is the number. 9 panels = 350v; 26 panels = 350v. Basically instead of voltage being progressively stepped up the solar edge 'magic' essentially steps up current AND voltage...

    Clear as mud? :confused:

    Youtube to the rescue....

     
  17. Garlan Garner

    Garlan Garner Active Member

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    That couldn't be more wrong.

    SolarEdge is the furthest away from a string inverter system than you can get.

    Each panel works independently - Which is the total opposite than what a string inverter system does.

    Where are you getting your information from?

    With SolarEdge...you can have a fully covered panel without affecting any others that are in full sunlight.

    Just look at my array.....Its proof. Click on the progress in my signature and look at my panels. I have live proof.
     
  18. Garlan Garner

    Garlan Garner Active Member

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    You don't need a video. Look at my system. Its live. Its certainly not a string inverter system - not even technically.

    I'm passionate about this because I teach this to kids in high school every day.
    :Lets not be misleading to people in this forum.
     
  19. nwdiver

    nwdiver Active Member

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    #19 nwdiver, Sep 7, 2016
    Last edited: Sep 7, 2016
    String inverter simply means that DC-AC conversion occurs at the string level. Solar edge splits MPPT function and inverter function. MPPT occurs at the panel level... inverter function at the string level. (String Inverter)

    I'm totally in favor of Solaredge. I love the technology but the cost needs to come down before I can use it on my lower cost systems.

    I 100% agree that panel level MPPT is better but it's only marginally better if all the panels are on the same plane and for most applications it's not $60 per panel better. If you have a complex roof where panels face in different direction then panel level MPPT is more valuable is spending $60 per panel is probably worth it.
     
  20. Garlan Garner

    Garlan Garner Active Member

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    That is not what string inverter means.

    First of all a string inverter system does not consist of optimizers nor micro inverters. Period.

    A string inverter is just what it says. Its a string of solar panels connected one to another in series - connected to an inverter. That's it. Nothing more and nothing less.
     

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