Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

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  • newenergynewenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    It was easy to work on because the MC connectors are easy to put together and take apart. It doesn't violate space requirements, unless I'm wrong about the extra size of the connector not counting against anything. If you pull on the wires a bit the slack comes out of the conduit run and you can disconnect and reconnect them pretty easily.

    The tape is just tape. We tape things partly to mark grounded and ungrounded and we are just in the habit of taping MC3s as we did that to help secure them and protect them from the weather outside of jboxes. The MC4s lock and the modules on that job used MC4s, but they are huge and wouldn't fit in the box.
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    icarus wrote: »
    Any news on this yet? Are you up and running? How are the numbers?

    Tony

    I'll have an update coming shortly. Summary:

    System passed City inspection after more grounding wiring, directly to a new grounding rod, was added.

    System's not turned on yet. A number of steps yet to go. Next step is to receive 'interconnect' paperwork from utility and turn it over to installer.

    Local television station is coming today for a film session. Thus system is turned on for today for demonstration purposes.

    Instrumentation implementation is complete.

    Will provide detail shortly.

    Best regards,

    Bill
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    newenergy wrote: »
    I did the most recent roof transition box like this. What do you think?

    mcinbox.jpg

    I think it looks pretty good. My only nit-pick is that I would have tried (tried...no guarantee of success) to ram that grounding conductor down to the bottom (Back? Top? Whatever.) of the box so that it isn't tangled up with the current carrying conductors.

    But I had to work at finding anything to nit-pick about. :D

    Oh wait! I found another thing to nit-pick!

    How come you used black tape on that one connector instead of red? (For anyone who didn't get it, that was a joke.)
  • SpartanScottSpartanScott Solar Expert Posts: 41
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »

    original.jpg
    Best regards,

    Bill

    Hi Bill, I've got a question for you. I am also going to be using WEL and the Wattnode on my system. In your picture above, which I've grabbed from your post #114, what exactly is the gray box between your wattnode's? Is this a fuse box for the G, N, & Line Voltage pulls? Is that a phone line you are using for the pulse signal from Wattnode to WEL? Great clean looking install by the way. Could you share with us the CT sizes that you are using?

    Thanks
    -Scott
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    ... I am also going to be using WEL and the Wattnode on my system.

    In your picture (below) ... what exactly is the gray box between your wattnode's? ...

    Is that a phone line you are using for the pulse signal from Wattnode to WEL?

    ... clean looking install by the way.

    Could you share with us the CT sizes that you are using?

    Scott, here you go. Below is an updated image of the picture you highlighted. It shows the additional/changed power/energy transducers I needed to integrate in solar PV into my energy monitoring system. All items are in a garage, on inside wall opposite the utility meter, PV kWh meter, and the PV AC Disconnect switch.

    original.jpg

    To specifically answer your questions:

    The gray box between WattNodes is an X10 signal amplifier/repeater, needed to help X10 signals cross over to the other side of the single-phase 3-wire service. It's manufactured by ACT. I have a whole house automation system that controls various things. Lighting is controlled using X10 power-line signalling.

    Nothing special is needed for connection of the WattNode pulse output ports to the WEL input pulse ports. I'm using CAT3 (telephone) cable.

    The installation may be clean but it's not completely to NEC standards. Inside the service panel box it is - the current transformers (CTs) and associated low voltage wiring are all UL Listed for example. But simply nailing/screwing the power transducers to the garage wall is not, as 220 VAC terminals are exposed (I have tape over them). This garage area is an extremely low traffic area in my personal home. An installing company would need to put the power transducers into an enclosure of some kind, either flush to the garage wall or surface mount.

    Details on my CTs, particularly sizing, are as follows:
    1. Incoming electric service / solar PV export = 100 A (200 A service panel rating, but, my electric consumption never gets above 100A. Using 100 CTs gives me 2 watts / pulse resolution, which helps on the PV export channel).
    2. Pool = 50 A
    3. Geothermal heating/cooling units = 50 A (I'm monitoring 2 units using one power transducer)
    4. Solar PV output = 30 A
    5. CT hole sizes are as small as possible to insure snug fit around wires.
    6. CTs are solid core (vs. split core) for increased accuracy. Note this means that more than likely you'll need to pull the meter before you install the CTs for incoming electric service / solar PV export.
    Hope this helps.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    icarus wrote: »
    Any news on this yet? Are you up and running? How are the numbers?

    Tony

    I'll use this weekend to get caught up to date. Considerable progress overall.

    The first City inspection went fine, with the only requirement noted before a re-inspection was labelling needed to be increased. A warning sticker to not move the PV back-feed circuit breaker was added to the outside of the service panel. A sticker was also placed on the outside of the inverter, with its various DC and AC capacities and limits noted.

    We got surprised by the second City inspection, thinking that all that would be re-inspected were the newly placed labels. Instead, the City asked for additional grounding connections, and asked for re-inspection again.

    What was asked for was 3 things:
    1. A new grounding rod.
    2. A new unspliced #6 insulated ground wire from the new grounding rod to the inverter's AC Ground terminal.
    3. Another unspliced #6 insulated ground wire from the same grounding rod to a panel rail.
    As a result, I now have another ground rod, this one is 4' long galvanized steel, and about 10' away from the ground rod at the service entrance. Here are some images, starting from the ground rod to the inverter's AC ground terminal:

    original.jpg original.jpg

    original.jpg original.jpg

    The inverter's AC ground terminal is in the upper right corner of the last image.

    Grounding theory for on-the-roof solar PV systems is not something I understand. Thus, I'm not able to explain what purpose this additional grounding serves.

    Best regards,

    Bill
  • newenergynewenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    I don't like the egc exposed on the wall. It needs to be protected from physical damage. I think the rule is egc smaller than 6awg must be. Generally, that portion would be armored cable. Also. What fitting is used where the wire leaves the enclosures?

    Also, is that grey wire an ok color for the ungrounded dc?
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    newenergy wrote: »
    I don't like the egc exposed on the wall. ... I think the rule is egc smaller than 6awg must be.

    ... What fitting is used where the wire leaves the enclosures?

    ... is that grey wire an ok color for the ungrounded dc?

    Thank you for your comments, newenergy.

    What would you use to protect the EGC? If I were to put in some EMT, is EMT suitable from a rust avoidance perspective?

    The DC wires in the early posting (inside DC Disconnect Switch) are yellow and grey, as required by my AHJ: "Residential interior PV direct current ... conductors shall be identified by system to comply with NEC 2008 section 210.5 (C). Direct Current ungrounded conductors shall be Orange, Yellow or Brown. The grounded conductor shall be identified by the color Gray."

    No fitting was used for the EGC travelling through the AC Disconnect Switch enclosure. See picture below. I would appreciate a suggestion for what I should install. Thanks.

    original.jpg

    Best regards,

    Bill
  • solarteksolartek Solar Expert Posts: 69 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    Thank you for your comments, newenergy.

    What would you use to protect the EGC? If I were to put in some EMT, is EMT suitable from a rust avoidance perspective?

    <snip>

    No fitting was used for the EGC travelling through the AC Disconnect Switch enclosure. See picture below. I would appreciate a suggestion for what I should install. Thanks.

    For the EGC from the rod to the box I would have used bare #4 so I wouldn't have to protect it. And I would have used a cord grip to transition into the box.


    (Mod: Feel free to remove the link for the cord grip. I just didn't see a product like it on the Wind-Sun store site.)

    Scott.

    Scott--perfectly OK to add links to any relevant site. -Bill "moderate moderator" B. :D
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    OK, one week ago I was authorized to turn on the system. And a couple of days ago a new utility kWh meter was installed.

    original.jpg

    Here's a first 7 days performance summary.

    The first thing to look at is daily output. For a Feb. day, with no clouds, the 8.1 KW (DC) system produces about 30 kWh, with output decreasing as a function of increased ambient temperature. This chart shows the output for the past 7 days:

    original.jpg

    The first day had some slight clouds late in the afternoon. The next 3 were cloudless days, and the past 3 (and again today) have been cloudy and rainy. The 1st cloudless day (2nd day shown) had a low/high of 30/50°F, the 2nd 32/55°, and the 3rd 33/63°. Clearly temperature affects output.

    The second thing to look at is instantaneous power. Here's the chart for the 2 coldest / cloudless days (2nd and 3rd days from the above chart):

    original.jpg

    The highest output was 6274 W at 2:16 PM (Dallas time) for the 1st day shown (coldest cloudless day). The highest output for the 2nd coldest cloudless day was 5896 W.

    Using PVWatts default values and assuming all default conditions to arrive at its 77% DC to AC Derate Factor (no shading, tilt at default Lat., and azimuth at 180°), a theoretical 8.1 KW DC system (36 panels @ 225 W ea.) should theoretically produce 6237 W.

    The utility companies in TX, to authorize rebates to installers, require systems to produce at least 80% of PVWatts' estimated kWh energy. Applying this same 80% number to instantaneous power output, the minimum would be 4990 W.

    With 2 data points now for my Wintertime, cold temp highest daily power output (6274 and 5896 W), it appears that Wintertime instantaneous performance is above this 80% 'floor.'

    The 3rd and last thing to look at is direct comparison to PVWatts' estimated kWh output on a monthly basis. With this being a partial month to run the solar PV system, it won't be meaningful to do a comparison this month. Here's the chart to do the monthly monitoring:

    MonthlySolarProduction.gif

    PVWatts says, for my location, taking into account past weather patterns, and using 77% default inputs, for a theoretical 8.1 KW DC system, Jan. and Feb. output should be, on average, 817 and 772 kWh respectively. Applying an 80% minimum expectation, this says the performance measurement should be 654 and 618 kWh respectively. On the chart, the 654 kWh number for Jan. is indicated (black line). When Feb. finishes, it will peak at 618 kWh.

    March will be the first month available to start meaningful monthly measurements. PVWatts estimates output to be 999 kWh; the 'floor' is 799 (80%). This will get tracked on the chart (the chart shown above is dynamic and will continuously update in this thread).

    Best regards,

    Bill
  • icarusicarus Solar Expert Posts: 5,157 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Congratulations, I am sure it is nice to see some return after all this effort.

    Tony
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    icarus wrote: »
    ... nice to see some return ...

    Tony

    Tony, thanks for the note.

    An interesting subject, once some longer term data is available, is the economics of my lower cost design - one large inverter for all panels with multiple panel orientations (azimuths) and panels across multiple orientations in a string (vs. a more expensive design with a dedicated inverter for each panel orientation). Since I'm not privileged to know what panel, inverter, piece-part and labor pricing is to an installer, I'll have to use the 80% threshold as the yes/no design economic indicator.

    The economics of having a much larger PV system than needed in TX will also be interesting. With no Net Metering requirement in TX, I'll have to continually shop around for the best rate to sell my exported power to. So far this month, for example, I've exported 40% of my PV output.

    And lastly, the subject of lease-purchase verus up-front-purchase will be interesting. I've had no capital outlay yet. Monthly cash flows will include:
    • Expense - Consumption from the grid at 10.3 cents (current 12 mo. rolling avg kWh rate).
    • Expense - PV production at 7.2 cents (current 12 mo. rolling avg rate)
    • Income - Export to the grid at 7.5 cents (fixed)
    I'll set something up so that it's easy to see if the economics are working.

    Best regards,

    Bill
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    OK, one week ago I was authorized to turn on the system. And a couple of days ago a new utility kWh meter was installed.

    original.jpg
    Shouldn't take long for that meter to read negative at your current usage/production rates if it doesn't already.

    Thanks for all the detail/pics - been very informative.
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    drees wrote: »
    Shouldn't take long for that meter to read negative at your current usage/production rates...

    I've learned that this new technology meter has 2 registers: power consumed from the grid, and power exported. So it can't 'spin' backward.

    I'll pay 10.3 cents (variable rate) to the utility co for power consumed from the grid (net of my consumed solar power), the first register, and I'll receive 7.5 cents (fixed rate) for power exported (2nd register).

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    solartek wrote: »
    ... I would have used a cord grip to transition into the box.

    Scott, thanks for the example illustration. I'll go obtain something like this.

    Best regards,

    Bill
  • System2System2 Posts: 6,290 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Bill,

    Good work! I've been lurking and following you install for several weeks now.

    You might want to consider switching to Kinetic Energy and make them your electrical provider:

    http://www.kinetictx.com/

    Kinetic is a Texas REP that will recognize net metering. As long as you're not dumping more back to the grid than you're taking, Kinetic will credit your electrical generation at the same price that you paying for it. Last I checked, they were charging about 10 cents/kwh and you can select any of their plans. 10 cents/kwh is far better than what TXU pays and should help your economics.

    I suggest that you contact them.

    Once I get my system running, I will make the switch to Kinetic.

    Monte
    Houston, TX
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    be sure that the electric company that owns the poles and lines are not going to charge any fees or percentages on your power in going with another company and lessen or negate any savings. they do that here (or they did a few years back) and that stopped me from switching as the charges the original company placed upon the other company (passed to the consumer of course) made the power more expensive and not less even though the other company in competition has lower base costs per kwh..
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    phleas wrote: »
    ... You might want to consider switching to Kinetic Energy and make them your electrical provider

    ... Kinetic is a Texas REP that will recognize net metering.

    ... Last I checked, they were charging about 10 cents/kwh

    ... you can select any of their plans.

    10 cents/kwh is far better than what TXU pays and should help your economics.

    Monte, thanks for the note. Interesting.

    As far as I know, Kinetic and Green Mountain are the only utilities (Retail Electric Providers - REPs) that are offering net metering.

    The last time I had checked on both Kinetic and GM, they were charging a higher monthly rate than TXU (I presume to cover net metering costs). I'm pleased to see their monthly rate now is more in line with TXU's.

    I believe for Kinetic, to get net metering, your plan selection options are limited to their 'Simply Green' plans. Still, a 12 month Kinetic Simply Green plan at the moment is 10.1 cents, about the same as TXU's Market Edge plan that I'm on.

    Reading the fine print, though, it looks like Kenetic buys exported power down at 7.02 cents, worse than TXU's purchase commitment at 7.5 cents. It seems Kinetic won't 'net meter' the 2.64 cents portion (of the 10.1 cents total) that goes to Oncor (our Transmission Delivery and Service Providor - TDSP). Nor is there any offset on $8.57 of base charges.

    I'll study more of the fine print to determine if indeed Kinetic's a better deal than TXU. At first glance, though, it does not seem so.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    niel wrote: »
    be sure that the electric company that owns the poles and lines are not going to charge any fees or percentages on your power in going with another company and lessen or negate any savings. ...

    Yep, see my comments just posted above.

    Thanks Niel.

    Best regards,

    Bill
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Today was a nice clear cool day in Central Florida, my 8kw array made just over 50kw today. I thought you could compare this to your generation and get a clear view off the shading hit your system is taking.

    All combined ( all four arrays 1kw, 5kw, 4kw, 4kw ) harvested 87,800 watts ... put a good dent in the deficit I've been racking up with the wacky winter weather we have had
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    Today was a nice clear cool day in Central Florida, my 8kw array made just over 50kw ...

    SG, thanks for the comment (I assume you meant to write 50 kWh, by the way). I'd like to understand better.

    I looked up where Bartow is (saw this from another thread) and concluded that Tampa is the closest to you for the cities PVWatts offers.

    My question is, how can I use PVWatts to estimate the theoretical peak one day kWh production from a PV system?

    Let's say that your 8 KW (DC) system is right at the PVWatts' default for grid-tie-only (no shading, 180° azimuth, 28° tilt). How do I compute your DC to AC Derate Factor, given you have 8 KW going in and 50 kWh collected over an entire day? Is it right at 0.77, or even better?

    Or said another way, if I assume the default 0.77 for grid-tie-only (and no shading, 180°, etc.), for 8 KW of panels, what's the best single day harvest possible in the month of Feb.? Is it right at 50, or is it higher/lower?

    Thank you for your expertise - I have much appreciated it.

    In my case, yesterday was a perfect weather day - cold, and no clouds. For my 8.1 KW system, I got 32.5 kWh for the day. We know why I'm lower than you. What I'd like to do is compute what I could be getting with a no shade / 180° / default tilt system to compare my actual to, to understand, on a full sun day, how much my shade and design simplification is costing me.

    Many thanks.

    Best regards,

    Bill
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    PVwatts is a good tool for conservative harvests averaged over months or years. right about now PV watts puts our locations at @ 5.0 sun hours ... it also uses the average temperature, so days like today that were 25 degrees below normal and perfectly clear are not the average

    The reason I posted my number is this is the best it comes to getting a apples to apple comparison to a ideal vs what you have and a real world percentages.

    My system is running on GT5.0's , roof is 23 degrees facing 235 degrees ( South- South West ) The PV Watts 0.77% has a bunch of factors that doesn't match our/your conditions, for example, its takes off ( default values ) 5% for dirty panels, 5% for the panels below STC performance ( Evergreens are -2% and Mine seem more like STC ) 8% on the inverter ... I went in and changed the defaults and I come up for 88% based on my actual system and conditions.

    Now, the average Sun of 5 hours, 8kw * .88 = 35kwh average .. but PVwatts, this include days of rain , over cast ect ... 6 day of rain days is a 20% hit in the average sun-hours , ( 24 / 30 ) or the power on non-rain days would be 44Kwh ... which would be inline with today performance when you factor in the very cool and windy temperature

    Back to your system, we had very similar days in irradiance and temperature, if anything it was colder in TX. You have all brand new panels so any difference is your panel angle ( your roof is a steeper pitch ) and shaded strings parralled with no shaded strings. The Angle is a cos-sine function, figure 10 degrees, that about 2% hit so the rest has to be your strings and shading. Your system is running over a clear day at 66% of what the panels are capable compared to mine, or another way to say this is if yours they were at the same angle ( you have south and west mixed strings ) and not shaded ( you have lots of severe shading ). Its doesn't get any better than this for apples to apples comparisons
  • System2System2 Posts: 6,290 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Bill--

    Thanks for your mail. I have contacted Kinetic and you can select any plan if you wish to net meter (got it in writing from them). I will have to ask if the 3.19 cents/kwh for Centerpoint's TDSP portion is included. I will let you know what I find out.

    Over the past 3 yrs, I have been very diligent in conservation measures and have reduced our household electrical consumption from 13000 kwh/yr down to 8500 kwh/yr. My house is 3340 sq ft with 4 people. I have no pool. Your usage is considerably higher than mine...28000 kwh/yr would last me 3 years!

    I plan to start very small (maybe 700-1000 watt system using Enphase microinverters). I predict that I'll be dumping 30-50 kwh/mo back to the grid. Once PV prices fall and Texas become more netmetering friendly, I'm planning to have about 7-8 kW on my roof. I have no shading issues.

    Using the latest on TXU and Kinetic websites (plus powertochoose.org) for the cheapest 12 month fixed plans (which I prefer), I still come out ahead with Kinetic. I assumed that the 3.19 cent portion did NOT net meter. I've attached my back of the envelope calcs.

    Regards,
    Monte
  • GreenerPowerGreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    I'll pay 10.3 cents (variable rate) to the utility co for power consumed from the grid (net of my consumed solar power), the first register, and I'll receive 7.5 cents (fixed rate) for power exported (2nd register).
    Texas is a "monthly net-metering" state. Each monthly billing cycle, they suppose to "net" the 2nd register with the 1st register. If the net is a "sell", you earn at 7.5c/KWhr, if the net is "buy", you pay 10.3c/KWhr . If they just go according to the 2 registers as you described, this is billing trick and it's not "monthly net metering". You are supposed to be able to use your daily export to cover other day/time AC usage in the "monthly billing cycle".
    GP
  • System2System2 Posts: 6,290 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    I have received a response from Kinetic Energy and Centerpoint's TDSP charge of 3.19 cent/kwh is not net metered (as everyone suspected). See their response below.

    After doing the math in my case, my monthly bill will still be lower with Kinetic vs TXU or Green Mountain. My math also shows that once I become a bigger exporter, then Kinetics is not as favorable.


    "Hi Monte,

    We allow net generation for residences and small businesses. In short, you will be charged your TDSP charges on all kWh used, but only charged the Kinetic charge on the net usage. Currently Kinetic does not buy excess energy generated above your monthly usage. You are allowed to select any of our plans (monthly, 6 month, Green, etc...) and net generation pricing will apply.

    Today's rate for the Simply Green One Year plan is 10.52 cents/kWh with a $9.72 monthly charge (as an example). This is made up of the Kinetic energy rate of 7.33 cents/kWh and a TDSP/Centerpoint rate of 3.19 cents/kWh. Your "hypothetical" itemized usage is as listed below.

    Monthly usage- 800 kWh
    Generation- 100 kWh
    Net usage- 700 kWh

    Kinetic Energy charge .0733 * 700 kWh = $51.31
    TDSP Energy charge .0319 * 800 kWh = $25.52
    Kinetic Monthly = $2.70
    TDSP Monthly = $7.02

    Total Charges before taxes =$86.55"
  • BB.BB. Super Moderators, Administrators Posts: 29,369 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Generally, 1 year net metering is the best plan (if available)---allows you to move your excess charging (spring/fall?) to your times of heavy use (summer) and low production (winter).

    California (PG&E anyway) is changing--but the original plan was that they wanted the customers to have the panels supply a maximum of 100% of a home's usage over the 1 year period. Any excess at the end of one year was zeroed out. (looks like we will be paid--at what rate, I do not know yet--for any excess energy generated at the end of the one year period).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • newenergynewenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    BB. wrote: »
    Generally, 1 year net metering is the best plan (if available)---allows you to move your excess charging (spring/fall?) to your times of heavy use (summer) and low production (winter).

    California (PG&E anyway) is changing--but the original plan was that they wanted the customers to have the panels supply a maximum of 100% of a home's usage over the 1 year period. Any excess at the end of one year was zeroed out. (looks like we will be paid--at what rate, I do not know yet--for any excess energy generated at the end of the one year period).

    -Bill

    Sent to the CPUC I think to make up the rules and the rates. I don't think they are established yet.
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    ...Back to your system, we had very similar days in radiance and temperature, if anything it was colder in TX. You have all brand new panels so any difference is your panel angle ( your roof is a steeper pitch ) and shaded strings parralled with no shaded strings. The Angle is a cos-sine function, figure 10 degrees, that about 2% hit so the rest has to be your strings and shading. Your system is running over a clear day at 66% of what the panels are capable compared to mine, or another way to say this is if yours they were at the same angle ( you have south and west mixed strings ) and not shaded ( you have lots of severe shading ). Its doesn't get any better than this for apples to apples comparisons

    SG, much appreciate the comments. Looks like I'm down one-third from what I could be at if I didn't have any shading, and if I didn't have just one inverter serving panels at 2 different orientations (azimuths).

    I know where a couple pieces of the one-third are being consumed. I did a no shade PVWatts analysis, using my exact azimuths and tilt, and assumed I have separate inverters for each orientation. Result is I'm 8% down from an all panels at 180° and at ideal tilt scenario.

    Then, there's additional loss due to only having one inverter. And further loss due to shading. Thanks for adding it up to arrive at the one-third number.

    If I had an accurate irradiance meter, I'd do a science project to measure and integrate the readings, arrive at insolation, and then compare to panel output. I wish there exists a PVWatts equivalent reference that articulates, by location, cloudless day insolation as a function of day of year, at a given temperature.

    Thanks again.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    phleas wrote: »
    ... you can select any plan if you wish to net meter.

    ... Using the latest on TXU and Kinetic websites ... for the cheapest 12 month fixed plans (which I prefer), I still come out ahead with Kinetic. I assumed that the 3.19 cent portion did NOT net meter. I've attached my back of the envelope calcs.

    Monte, thank you.

    My rolling 12 month average rate is 10.1 cents, considerably lower than the 13.0 cents you assumed in your analysis. This plus noting that Kinetic doesn't pay on the TDSP portion (as you commented in your later posting), it looks like I'm better off simply staying with TXU, paying 10.1 cents, and receiving 7.5 cents for everything I'm exporting.

    Plus, I will be a big exporter because I just can't use a lot of 6000 W during the day.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    Texas is a "monthly net-metering" state. Each monthly billing cycle, they suppose to "net" the 2nd register with the 1st register. If the net is a "sell", you earn at 7.5c/KWhr, if the net is "buy", you pay 10.3c/KWhr . If they just go according to the 2 registers as you described, this is billing trick and it's not "monthly net metering". You are supposed to be able to use your daily export to cover other day/time AC usage in the "monthly billing cycle".
    GP

    Thanks GP. This will be a pleasant surprise if indeed this is correct.

    Another look at the papers I recently signed suggest that I will not receive monthly net metering:

    "Customer expects to generate Power in excess of its needs at certain times during the monthly billing cycle ...

    " Customer will sell to Company all monthly Out-flow generated ...

    " Company may choose either to provide a credit on Customer’s monthly electric bill or make payment, on at least a quarterly basis, to Customer for the purchase of the monthly Out-flow ...

    " ... the TDSP will transmit the quantity of the Out-flow during the monthly billing cycle, ... to Company at the same time the TDSP transmits Customer’s consumption quantity to Company. Company shall credit/pay Customer for Customer’s monthly Out-flow as provided in Exhibit “A” ...

    " Exhibit A: For Out-flow associated with an ESI ID that has been assigned a solar ERCOT load profile, the price will be $0.05 per kWh. There also will be an additional premium equal to $0.025 per kWh, for a total price of $0.075 per kWh."

    After some time passes by to get some bills, I'll post here what actually results.

    Best regards,

    Bill
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