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  • Solar Planning Question(s) (Yes, I'm new here)

    After retiring earlier this year, my wife and I decided to dramatically downsize our home. We're in the "we can still change things" phase of planning a new home build. Since this will likely be our last home, and plan to be here a long time, one of the items on our wish list is a PV array that will offset as much of our electric bill as possible. Even though I have a technical background, I know little about residential grid-tied PV systems. Naturally, I began my research on the web, which led me to this forum.

    We have come to the conclusion that we should complete the house and live in it a while before installing a PV system. This decision was driven by several factors:
    • Our builder knows less about PV than we do and is not comfortable being involved in the install.
    • Our "old" house is vastly less energy efficient than the "new" house will be. Aside from old (read: poor) insulation, the old house is all electric. The new house, on the other hand, has natural gas available for HVAC, water heating and cooking.
    • We live in Texas, where incentives are not as prevalent or large as some other states.
    • Our PoCo, Xcel Energy, seems to restrict PV system size based on historical energy consumption (since the house will be new, we need to "build up" some history).
    • We do NOT want to delay the start of construction.

    As the title says, I have some planning questions that I hope more knowledgeable and experienced forum members can help us with:
    PV Preparations
    Our builder suggested that the electrical for the house could be designed in anticipation of a future PV installation, but he's looking to me to identify what those might be. What sorts of things could we do? Main breaker box/panel choice? Wiring run(s)? Roof Pitch (one of the roof segments will face due south with zero shade)? Others?

    Xcel Energy
    Does anyone have experience with grid-tie to Xcel Energy IN TEXAS. From what I've read thus far, what Xcel does and allows in Texas is very different than what they do and allow elsewhere. Colorado, for example, seems to be more renewable friendly than Texas, offers more to the consumer and demands more from PoCos. How Xcel is to deal with when it comes to grid-tie? Do they actually restrict system size? What do they actually pay for power fed into their system? Any other insights?

    I'm sure I will have more questions as my knowledge increases, but I'm still doing my due-diligence and am still very much in the learning phase of this project. I welcome any and all input. Please also correct me if I've drawn incorrect conclusions from my (limited yet) research.

    Thanks in advance,

    Tenaya

  • #2
    Hi Tenaya and welcome to solar panel talk.

    I am sure someone here has experienced doing solar in Texas, not me though. There are a few websites that have the rules and regulations for solar installs in different states, good luck, cheers.

    Comment


    • #3
      First thing to understand in TX electric is deregulated and there is no Net Metering Laws in TX except for Austin. Right now in TX electricity is inexpensive and rates will continue to go down for the next few years as TX has more energy than what they know to do with. Going prices is around 8-cents per Kwh delivered.

      Xcel I believe is a Generator, so you do not buy from them. In TX you pick you retailer. All they do is shuffle paper and money or act as an agent for the utilities. For example Green Mountain Energy is one that offers Grid Tied in some areas of the state. They will only pay you wholesale price for any excess you generate, and charge you retail for any you buy. Where I lived in DFW area we paid 7.6-cents per Kwh for up to 2500 Kwh, after that the rate drops to around 7.2 cents per Kwh. Exact opposite of most states do where the more you use the higher the price is. Green Mountain and one other retailer offered grid tied. They bought excess for around 5-cents, and you pay 12 cents for what you use. Couple that with no incentives from you rneighbors paying for your system can easily result in you just paying a lot more for going solar.

      Another thing to consider is if you should sale your home in TX. Solar does not add much of any value to your home, and can eliminate a lot of potential buyers leaving you a home that takes a lot longer to sale at reduced prices. So you really need to do your homework and call the retailers and see what the details are. TX is not friendly to solar as there is really no need for it because electricity is dirt cheap and plentiful. Sounds like you might be looking out around Amarillo because that is th eonly place I know Excel to operate with a Generating plant out there. I don't think they are retailers but not certain.

      Good luck.
      MSEE, PE

      Comment


      • #4
        Originally posted by Sunking View Post
        First thing to understand in TX electric is deregulated and there is no Net Metering Laws in TX except for Austin. Right now in TX electricity is inexpensive and rates will continue to go down for the next few years as TX has more energy than what they know to do with. Going prices is around 8-cents per Kwh delivered.

        Xcel I believe is a Generator, so you do not buy from them. In TX you pick you retailer. All they do is shuffle paper and money or act as an agent for the utilities. For example Green Mountain Energy is one that offers Grid Tied in some areas of the state. They will only pay you wholesale price for any excess you generate, and charge you retail for any you buy. Where I lived in DFW area we paid 7.6-cents per Kwh for up to 2500 Kwh, after that the rate drops to around 7.2 cents per Kwh. Exact opposite of most states do where the more you use the higher the price is. Green Mountain and one other retailer offered grid tied. They bought excess for around 5-cents, and you pay 12 cents for what you use. Couple that with no incentives from you rneighbors paying for your system can easily result in you just paying a lot more for going solar.

        Another thing to consider is if you should sale your home in TX. Solar does not add much of any value to your home, and can eliminate a lot of potential buyers leaving you a home that takes a lot longer to sale at reduced prices. So you really need to do your homework and call the retailers and see what the details are. TX is not friendly to solar as there is really no need for it because electricity is dirt cheap and plentiful. Sounds like you might be looking out around Amarillo because that is th eonly place I know Excel to operate with a Generating plant out there. I don't think they are retailers but not certain.

        Good luck.
        Thank you for the responses.

        Yep, deregulation, ain't it wonderful?

        You're right, Xcel is a generator, but they are also the company we buy power from. We deal directly with them, they send the bill, and we make the check out to them (old school). From what I can tell, there is no other choice. The retailer model is certainly in effect down south (Austin, Dallas, etc.), but I doubt there are enough customers for it to work here (Amarillo metro area is only around 250K residents; Canyon is tiny and Lubbock metro is every so slightly larger at 300K).

        I realize we're blessed with low Kwh prices, but given the long time we plan to live in the home (10, 15, maybe 20 years or more), zero sounds nice. I understand the short term forecasts, but we'll be in this house for the long term and I struggle to accept that any commodity will go down in price.

        I'm not particularly concerned that Solar doesn't add much to house values here and am not using it in my calculations.

        Tenaya

        Comment


        • #5
          Originally posted by Tenaya View Post
          PV Preparations
          Our builder suggested that the electrical for the house could be designed in anticipation of a future PV installation, but he's looking to me to identify what those might be. What sorts of things could we do? Main breaker box/panel choice? Wiring run(s)? Roof Pitch (one of the roof segments will face due south with zero shade)? Others?
          How big are you thinking?
          9.6kW or smaller you can do a 40A or smaller breaker end-feeding a 200A main panel (40A breaker at one end of the panel connected to the solar, 200A main disconnect at the opposite end)
          If you want bigger, you have to either use a smaller main breaker (ex. 150A main breaker, would allow you to have a 90A solar breaker)

          OR you install a 400A main panel.
          homedepot has 400A meter/main panel for $700 vs. $150 for the 200A version.
          And then I think that one is actualy that it has a pair of 200A main breakers/main shutoffs - one for the built-in 200A busbar, and one for feeding to a separate 200A subpanel. If you go that path, then you could have the subpanel be a dedicated panel just for the solar.


          I'd lean toward the 400A main.
          But then I'm spending *your* money, not mine.

          Where's the main panel and meter going to be located?
          Ideally they'd be on the north side of the house with wall space adjacent to them where you can put the inverter.
          (best to have the inverter not have direct sunlight on it)
          Another option might be in the garage. (ex. meter is outside the garage, main panel and inverter are on inside wall)
          Maybe with a drawing of layout of the house (roof, main panel & meter location & orientation (which way's north?)) others might have better suggestions.

          Last suggestion I'd have - think about how you'd run conduit from your inverter location to the panels on the roof. And make sure that you'll be able to access that space - ex. no dead-space attic that you can't get into without tearing a hole in the living room ceiling. You could run conduit ahead of time if you have confidence in what you'll do. Can do conduit up through roof into bottom of a "Soladeck" roof mount box. There might be other/better option for the roof penetration - Soladeck is one I know of that I've seen used... I've also seen conduit come up and into a LR conduit elbow or a J-box just above the roof penetration. And of course figure out how to get that conduit to the spot where your inverter is. And if your inverter isn't going to be right by your main panel, then I think you'll have conduit from the inverter to the main panel (so you'll need to figure that out too)
          And if you install conduit now, I'd go with at least 3/4" conduit - maybe 1".
          Installing conduit now *may* be a really good idea - especially where you want it installed inside of a wall - as you wouldn't have to open up the wall (remove siding? break up stucco? remove bricks? Or from the inside, cut open drywall and repair and patch)

          Possibly you can call up a solar installer in the area and ask them if they'd be willing to go over your plans with you if you pay them an hourly amount (maybe $100 for an hour of their time?) The problem is going to be getting someone who *isn't* just a salesman - but rather someone who can look at where conduit would be run, where the inverter would go, etc. etc.

          Oh - and I'd say put plenty of room in your attic so you can easily store crap up there as well as do things like run conduit. Make the attic space be an area you can stand up in (and store the christmas decorations, and store all the things you can't bear to throw out) You'll thank yourself later for doing it - and adding it now during planning stages, it'll probably cost less than a month or two of storage at a storage locker.

          Comment


          • #6
            Welcome.

            First, about all the prep you need to do, is install a large enough Service Panel, that has enough electrical ampacity to handle the solar without overloading the buss bars.

            Another prep, would be to install conduit to an 2nd panel that the solar will feed and act as emergency cut-off Local code and utility will be able to advise you about the specifics. And stub out conduit to the location of the proposed solar inverter.

            This is the time to decide about "critical loads" and route them to a sub panel that can connect to a Transfer Switch, so you can safely use a generator in case of grid failure. Backup generator is much less than backup batteries, unless you are planning for the end of the world. If you do want battery backup, you will need a high voltage charge controller, and a Hybrid inverter. All this can be roughed in, so you don't have to tear up walls later. And build a site for the batteries. And for the generator to keep the batteries charged in case a storm knocks out power, and it's cloudy for 5 days.

            Be sure the roof will be strong enough for the added weight of the PV panels, have Engineering add a note specifying this, you will need that note when applying for solar permit in 2 years. (after the tax incentive runs out)
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

            Comment


            • #7
              Originally posted by Mike90250 View Post
              This is the time to decide about "critical loads" and route them to a sub panel that can connect to a Transfer Switch, so you can safely use a generator in case of grid failure. Backup generator is much less than backup batteries, unless you are planning for the end of the world. If you do want battery backup, you will need a high voltage charge controller, and a Hybrid inverter. All this can be roughed in, so you don't have to tear up walls later. And build a site for the batteries. And for the generator to keep the batteries charged in case a storm knocks out power, and it's cloudy for 5 days.

              Be sure the roof will be strong enough for the added weight of the PV panels, have Engineering add a note specifying this, you will need that note when applying for solar permit in 2 years. (after the tax incentive runs out)
              FWIW, my building permit department has as a general rule that less than 5 pounds/sq. ft for solar doesn't require additional structural computations for the added weight of PV panels.
              The panels I'm planning to use are 16.8kg (37 pounds) and 17.65 square feet - so even after adding in racking it's still not anywhere close to 5 lbs/sq.ft.
              BUT you have to make your building dept happy (as well as satisfy your own concerns) - so check with your own AHJ (Authority Having Jurisdiction) - and at this stage, it's probably easy for you to get documentation that you'll be fine with weight & wind load from the panels.

              As for generator & batteries - I'm probably projecting my own plans onto this - but my assumtion would be no batteries, no generators. That if there were any generator for emergency preparedness, it'd just be a small one that'd be used for small loads via extension cords.
              BUT feel free to tell us what you're thinking Mike.

              Comment


              • #8
                Originally posted by foo1bar View Post
                FWIW, my building permit department has as a general rule that less than 5 pounds/sq. ft for solar doesn't require additional structural computations for the added weight of PV panels.
                The panels I'm planning to use are 16.8kg (37 pounds) and 17.65 square feet - so even after adding in racking it's still not anywhere close to 5 lbs/sq.ft.
                BUT you have to make your building dept happy (as well as satisfy your own concerns) - so check with your own AHJ (Authority Having Jurisdiction) - and at this stage, it's probably easy for you to get documentation that you'll be fine with weight & wind load from the panels.

                As for generator & batteries - I'm probably projecting my own plans onto this - but my assumtion would be no batteries, no generators. That if there were any generator for emergency preparedness, it'd just be a small one that'd be used for small loads via extension cords.
                BUT feel free to tell us what you're thinking Mike.
                Usually, for PV, a bigger deal than panel weight on roof loading is the wind loading created by the panels which may be something like an order of mag. higher than the dead load, and depending on location, larger in a negative direction (uplift) than the other dead loads (snow) or the weight of the panels.

                Comment


                • #9
                  Originally posted by Tenaya View Post
                  After retiring earlier this year, my wife and I decided to dramatically downsize our home. We're in the "we can still change things" phase of planning a new home build. Since this will likely be our last home, and plan to be here a long time, one of the items on our wish list is a PV array that will offset as much of our electric bill as possible. Even though I have a technical background, I know little about residential grid-tied PV systems. Naturally, I began my research on the web, which led me to this forum.

                  We have come to the conclusion that we should complete the house and live in it a while before
                  installing a PV system. This decision was driven by several factors: Tenaya
                  If you have an air conditioner, you might consider a geo thermal heat pump with buried
                  outside heat exchanger. This will be more efficient than an air to air unit, and can be
                  quite good for heat some seasons as well. It can run on your cheap electricity, or the
                  PV power you generate if a decent net metering program is available. If its big enough,
                  it could supply heat all seasons. Bruce Roe

                  Comment


                  • #10
                    Originally posted by foo1bar View Post
                    ....
                    As for generator & batteries - I'm probably projecting my own plans onto this - but my assumtion would be no batteries, no generators. That if there were any generator for emergency preparedness, it'd just be a small one that'd be used for small loads via extension cords.
                    BUT feel free to tell us what you're thinking Mike.
                    Do you get ice storms that tear down 20 miles of power lines ? Tornados ? Texas size Hail ? 30 foot high balls of tumbleweeds?

                    Grid-Tie, only works while the grid is on. Otherwise, it's just fancy glass on your roof. You can get a high voltage charge controller (Morningstar & Xantrex make them) and charge a small battery bank to run an inverter that could keep a fridge, a fan, and computer going as long as you had sunshine. If you expect outages longer than a week. For a week, you run a generator which will cost you less than the HV CC, batteries & extra inverter.

                    But take your "backup circuits" (fridge, propane stove, hallway light, computer outlet) and route them to a "Backup panel" that is connected with a transfer switch, and you can easily power those wires with a generator, and not need a bunch of extension cords snaking in through the windows.
                    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister

                    Comment


                    • #11
                      Originally posted by Tenaya View Post
                      I realize we're blessed with low Kwh prices, but given the long time we plan to live in the home (10, 15, maybe 20 years or more), zero sounds nice. I understand the short term forecasts, but we'll be in this house for the long term and I struggle to accept that any commodity will go down in price.
                      I caution you to really think this through. Solar only pays off if multiple conditions are met.

                      You receive subsidies of 30 to 60%. In two years all subsidies will be gone.
                      High electric rates. TX does not have high electric rates, never has and will always be lower than most states.
                      Excellent Solar isolation values which TX does have.

                      ! out of three likely means you will never break even or live long enough to see it happen. So do your homework, its your money. I know dozens of folks in TX and OK that went grid tied and deeply regret it. Those that sold their house and used a loan to pay for it end up writing the check at closing. Their monthly electric bill increased 200 to 300% for 10 years. Instead of paying the POCO $150 per moth, they end up paying the POCO $50 per month plus a $200 to $350 a month loan payment for 10 years.

                      So be careful and do your homework. But you gotta love TX State Income Taxes and energy prices. No better state in the union to live and do business. No taxes, low cost of living, affordable housing, high wages, and no unions to speak of except around Austin where everything cost more and lower wages.
                      MSEE, PE

                      Comment


                      • #12
                        Can't believe that you guys are only paying 8c/kwh, while we, CA, pay ~ 40c at the highest tier. Makes me think that the government there is somehow subsidizing the energy industry, or ours is somehow taxing the industry to make alternative energy more attractive intentionally. At 8c/kwh, it's very hard to justify solar. My system has a generation value of 6c/kwh if works for 25 yrs without any problem.
                        16xLG300N1C+SE6000[url]http://tiny.cc/ojmxyx[/url]

                        Comment


                        • #13
                          Originally posted by thejq View Post
                          Can't believe that you guys are only paying 8c/kwh, while we, CA, pay ~ 40c at the highest tier. Makes me think that the government there is somehow subsidizing the energy industry, or ours is somehow taxing the industry to make alternative energy more attractive intentionally. At 8c/kwh, it's very hard to justify solar. My system has a generation value of 6c/kwh if works for 25 yrs without any problem.
                          Well in TX if you use more than 2500 Kwh per moth, the price goes down even more.

                          You are right government subsidies have something to do with it, but not the way you think. TX is an exporter of energy. CA imports more than 30% of its electrical energy. You pay more because you are enslaved by neighboring states who can charge what they want, and you also have to pay your neighbors bill for subsidizing their solar solar systems and Net Metering paying the customer retail prices when they can buy at wholesale elsewhere. In TX generation cost like most of the country is around 4 to 5 cents per Kwh. That puts retail at around 7 to 8 cents providing a nice profit margin.

                          That is what happens when your energy policy discourages growth. You end up depending on others to provide your needs and you get to pay for it. FWIW TX is not the lowest in the country. That honor goes to states like Wyoming at around 6-cents per Kwh.
                          MSEE, PE

                          Comment


                          • #14
                            If that $0.06 / kwh estimate is generated from some time value or LCOE type analysis, it isn't really valid to compare it to the price of today's grid electricity. The OP's electric rate would need to be projected forward under the same assumptions used to get the $0.06 / kwh number, and see how it looks. The average value over 25 years could be much higher or lower than today's rate, depending on the assumptions used.
                            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                            Comment


                            • #15
                              Originally posted by Sunking View Post
                              you also have to pay your neighbors bill for subsidizing their solar solar systems and Net Metering paying the customer retail prices when they can buy at wholesale elsewhere. In TX generation cost like most of the country is around 4 to 5 cents per Kwh. That puts retail at around 7 to 8 cents providing a nice profit margin.
                              The utility doesn't pay the customer retail prices for net metering. If the customer over-produces, they get paid at wholesale prices.

                              I believe your point is that the customer gets to "store" his power "on the grid" for free - which is certainly true.
                              But since solar PV is very small (and was even smaller when rates were creeping above $.30/kwh for the big utilities), it's just your bias that you point to that as a cause of higher prices.

                              My part of CA we pay $.107/kwh for the top tier residential.
                              So IMO it isn't really CA vs. other states - it's PG&E/SDGE being incompetent (or maybe competent, but low rates for their customers is irrelevant to them)

                              Comment

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