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How many watts in solar panels do I need for my grid tie system

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  • #16
    I really am glad I found this site. I have a lot to think about. Thank you for being patient with me.

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    • #17
      The problem I am having with this thread is that there is a lot of misinformation and down right incorrect information being distributed. see my comments below.

      Mod note - Removed comments - if you care to try again best stay away from the same thing you are accusing Sunking of - statements without obvious basis
      Last edited by russ; 07-17-2012, 04:08 PM.

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      • #18
        Originally posted by Sunking View Post
        For grid tied system you are going to have to go through the whole permitting and inspection process which is expensive. In addition using contract labor is going to be very high on small scale jobs upgrading, and inflation will cause it to go even higher.
        Yet another problem some people face is this:
        1. They install a small grid-tie system, with the intent to expand it.
        2. Then when the time to expand comes along, their original installer has either raised their rates astronomically trying to stay in business or has gone out of business.

        Quite often, when this happens no other local solar installer or even general electrician will touch the system since they had no part in the original installation and do not want to be on the hook for anything the first installer may have done wrong. That seems unfair to the homeowner, but it makes good business sense to the new company.

        Since grid-tie cannot be entirely DIY (engineering and trade sign-offs are required), this leaves the homeowner up the creek with a small system or else having to start over from scratch.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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        • #19
          Originally posted by inetdog View Post
          Yet another problem some people face is this:
          1. They install a small grid-tie system, with the intent to expand it.
          2. Then when the time to expand comes along, their original installer has either raised their rates astronomically trying to stay in business or has gone out of business.
          So don't do anything? This doesn't make sence to me. I am going to start small when I buy my new house next spring with the intent to expand it. I'm not going to sit on the sideline because one of these things might happen.

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          • #20
            Rdjntx Electric rates have fallen in TX steadily since 2008 when we peaked at 13.1 cents. My new contract for the next 3 years locked is 8.9-cents and I am pissed off because I can now get it for 7.7-cents had I waited. Read this and weep. Current rates for my area. I back my statements up with facts and documentation.

            There is no way anyone on this forum with knowledge of the industry is going to believe you get a 5 year payback in TX. Rates here are just to low, even in Austin. FWIW here are Austim Electric rates. Almost double than the rest of the state.
            MSEE, PE

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            • #21
              Originally posted by Sunking View Post
              Rdjntx Electric rates have fallen in TX steadily since 2008 when we peaked at 13.1 cents. My new contract for the next 3 years locked is 8.9-cents and I am pissed off because I can now get it for 7.7-cents had I waited. Read this and weep. Current rates for my area. I back my statements up with facts and documentation.
              There is no way anyone on this forum with knowledge of the industry is going to believe you get a 5 year payback in TX. Rates here are just to low, even in Austin. FWIW here are Austim Electric rates. Almost double than the rest of the state.
              that website also has the rates for dallas, houston, and san antonio and ft worth. ALL who have rates in line with Austin. http://www.electricrates.com/compare/ odessa rates 7 cents to 13 cents, Lubbock seems to have the cheapest rates of the municipality owned electric companies with an average of 7-8 cents. Bottom line while austin may be double the rates of SOME places to say that it is double the rest of the state is inaccurate. for a city of it's size it is right in line with the rest of the states larger cities and not anywhere close to double.

              As far as my 5 year break even point, if russ will provide me with an email address I will send the documentation to him and he can verify what I am saying.

              I am loathe to carry on much of a conversation with you since my previous post was deleted.

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              • #22
                Originally posted by Sunking View Post
                Rdjntx Electric rates have fallen in TX steadily since 2008 when we peaked at 13.1 cents. My new contract for the next 3 years locked is 8.9-cents and I am pissed off because I can now get it for 7.7-cents had I waited. Read this and weep. Current rates for my area. I back my statements up with facts and documentation.
                Have you checked out the rates in Panama? Odds are you're going to be even more pissed! Apparently, the government sets the rates based on the price of oil even though most of their generation capacity is hydroelectric. You'll likely pay triple what you do in Texas - based on prices a few years ago - but I think they just had another rate increase this month so who knows.

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                • #23
                  Originally posted by Ian S View Post
                  Have you checked out the rates in Panama?
                  Yep and Costa Rica. House will be smaller and we are looking for property in the higher altitudes there so that takes a big bite out of the electric usage. But yes electric is much higher but more than offset by the cost of living in either two countries plus no income taxes.
                  MSEE, PE

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                  • #24
                    Originally posted by daveb View Post
                    So don't do anything? This doesn't make sence to me. I am going to start small when I buy my new house next spring with the intent to expand it. I'm not going to sit on the sideline because one of these things might happen.
                    I am not at all saying to do nothing.
                    I was responding to the question of why experienced people on this panel do not recommend starting small and expanding later.
                    One alternative is to stretch yourself to get the largest possible system at the start.
                    Another alternative is to start small but to be aware at the start of the fact that eventual expansion may not be as simple as adding more panels and adding a second inverter.
                    Some of the other things mentioned about the difficulties of expanding later are not "might happens", they are "will happens".

                    Expanding an off-grid system is in some ways easier, but goes a lot smoother if forward-looking decisions (like using a 24 or 48 volt battery pack and inverter instead of a 12 volt system) are made at the beginning.
                    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                    • #25
                      Originally posted by daveb View Post
                      So don't do anything? This doesn't make sence to me. I am going to start small when I buy my new house next spring with the intent to expand it. I'm not going to sit on the sideline because one of these things might happen.
                      We are not telling you to do nothing. I assume you are looking at grid tied. If that is the case then use the micro inverters (an inverter mounted directly on the solar panel, one per panel) as expansions are easy.

                      But our points are not maybes. When it is time to expand, you will have to pay for a new set of permits and inspections, high labor rates for small scale jobs, and you only get one shot at the rebates. Inetdog is correct when he says if your solar contractor is out of biz, It will be very difficult or almost impossible to find an electrician or electrical contractor to expand it. The reason is because once they touch it, they own it and will be responsible for fixing any errors by the previous installer and bringing the whole system up to stricter code standards.

                      When you add up all the cost from upgrades pretty much destroys your chances of ever achieving an ROI. So we are not beating you up, but giving professional advice for FREE with no expectations of ever making a dime off you. We have no vested interest, and therefor can be completely honest, open, and forthcoming with you.
                      MSEE, PE

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                      • #26
                        I do appreciate the free honest expert advise. Thank you. It's funny you mention the micro inverters because I was just thinking about those and about to research them. They do seem like they would be the best for future expansion. And when I say start small I would start large enough for it to be worth the work. It's just I know I won't be able to start as large as I would like to finish. I'm sorry I should start my own thread. I dont think the original poster minds anyways.

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                        • #27
                          I'm new around here but have a little experience with "why not start small" aspect.

                          To do any system, you need permitting, grid interconnect, labor, ordering of parts, working through parts, replacing initial problem parts, wiring, etc. If you throw up 4 panels, it's is 90+% of the labor and work as a 40 panel system. The only add-on price is the parts of the larger system. Your cost per Watt installed goes down as the number of panels go up.

                          I've heard from installers say "doing a system of 2KW or less is not cost effective at all".

                          Now, if it is a DIY system, there are other options. You could buy a Sunnyboy 6000 and a single string of 10 panels, set it up and then in a few years, add a 2nd 10 panel string (of same spec) without too much "trouble". I think that is what daveb is saying. You wouldn't start with a SB 700U 3-panel system and then expand it because the inverter is too small, wiring too thin, breakers, and other bits will probably not work out.

                          In other terms - "cost of scale" is why it is usually smarter to try to size a system to maximize your goals and minimize your troubles. However, others are moderately right in terms of investing your money and hoping for better return than it being tied up in a Solar PV system. Take 50K and buy a 5% yielding bond for 10 years. Or, put it into a Solar PV system. After 10 years, the Solar PV is paid for and producing maybe $1200/year. The invested 50K will have grown to 81K. At that point, you can buy a Solar PV system and have 31K of loose change laying around to reinvest. We don't believe the price of Solar PV will go up that much in that same timeframe - in fact, panel prices (50% of the installation) have fallen annually so waiting another year might cost less to begin a DIY project. That mainly is panel prices, not inverters, wiring, labor (especially) and racking. All the non-panel costs are pretty flat or rising. One way to save big is to buy liquidation panels (Schott, etc.) who are out of business but distributors are selling them < $1/Watt.

                          Main problem for the above is many people don't have $50K cash laying around to invest either in a PV system or a 5% bond. They tend to finance the PV system and pay some sort of interest on it which also raises the costs of said system. This also makes return on investment longer.

                          I'm thinking of doing a 5600W DIY system. I'm still one fence if it costs more than $21K. I simply don't want to pay more than $4/Watt. A local installer I'm talking to tomorrow thinks his price is about $5.50/Watt and I'll probably just say no without wasting his time.

                          The installers used to use tactics of:
                          1) You're going to make $thousands every year on SREC sales (ah, no, not anymore).
                          2) You couldn't get 7-year ROI on any other investment (yes you can).
                          3) The utility will raise rates at 5% annually (not around here).
                          4) Today, I think they are doing mainly large-scale, sub $3/watt installs of 100KW or larger on buildings or farms. Businesses have the luxury today of doing fast-depreciation of equipment while homeowners cannot.
                          PowerOne 3.6 x 2, 32 SolarWorld 255W mono

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                          • #28
                            Originally posted by bonaire View Post
                            in fact, panel prices (50% of the installation) have fallen annually
                            That is not valid logic. The reason panel prices have fallen is because of massive over supply. Panels are selling way below manufacturing cost. Most manufactures have stopped production and slashed prices to get rid of inventory. Most will never produce another panel again. Once inventory is gone they will file bankruptcy and run with the money. You hear it in the news everyday. Once th eover supply is gone and free money is dried up supply and demand will come back into balance and panel prices will soar back to profitability for those manufactures that survive.
                            MSEE, PE

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                            • #29
                              Right - I'm not giving "reasons" for the price falling, just stating that they have fallen. Even new panel prices from existing vendors are coming out the door relatively cheaply. If demand goes up, so will prices and it's currently a buyers' market. I was recently quoted pallet pricing for Suniva 255W OPT panels for about $326/ea. Good prices, American made (so they say) and apparently 15.6% panel efficiency which is above average. I agree it's a temporary lull in the pricing marketplace, just as the US is seeing a Natural Gas dip in price too. All this will change over time.
                              PowerOne 3.6 x 2, 32 SolarWorld 255W mono

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                              • #30
                                Originally posted by Sunking View Post
                                That is not valid logic. The reason panel prices have fallen is because of massive over supply. Panels are selling way below manufacturing cost. Most manufactures have stopped production and slashed prices to get rid of inventory. Most will never produce another panel again. Once inventory is gone they will file bankruptcy and run with the money.
                                Agreed.

                                . . .and panel prices will soar back to profitability for those manufactures that survive.
                                Not a supportable statement. Manufacturers aren't stupid; they're not just giving up and waiting for bankruptcy. They are finding ways to make cheaper panels. China is learning how to make super cheap panels; Taiwan is learning how to get UL approval for their super cheap panels. They are doing this because they know there's a market for super cheap panels; the current massive uptake rates prove that. When the market recovers the price point will be far lower than it was in 2005 due to what manufacturers have learned.

                                The ones who can't do that, the ones who fail, will go out of business. The remaining producers will be making very inexpensive panels. That's the inevitable result of a maturing market - a shakeout that results in most companies failing.

                                Let's take another recent example - the 2000 Internet boom. A lot of companies started selling everything from net access to routers to cabling. Most are now out of business. The ones that survived are the ones who could build them cheaply and reliably. Prices didn't "soar" once that happened - they stayed pretty low, and today the cost for internet access (in megabits/second per dollar) is lower than ever.

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