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  • sizing equipment

    So I'm trying do decide on a system configuration, I have been monitoring my usage for years I seem to hover between 8 to 12 kW daily, varies somewhat with the seasons, but even on the high end if my math is correct it averages about 500 w per hour.

    My local poco has an app that lets you know your usage on an hourly basis I have had trouble signing into, so I'm speculating that I may spike up to 1000-1500 w at times and have periods of every little use, with that premise I'm working my way backwards thinking that I would need a 1500w peak inverter, a battery bank to support that load, but shopping around I am clueless which one is which

    I have not decided on a battery bank voltage, an beeing unfamiliar with these inverters I can't make a choice

    I'm hoping for some recommendations towards a product or another, a battery voltage

  • #2
    Why are you getting batteries at all? Grid tie will be much more efficient and better return.
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • #3
      Correct me if I am wrong but aren't those systems worthless when the grid is out?
      Plus last I looked into it the poco was buying watts for a fraction of what they sell it to you, but that's not even the main issue, I prefer to have my own stuff and not depend on the grid to come back on after an outage
      Last edited by georgerc; 04-25-2017, 06:25 PM.

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      • #4
        Most places have net metering in the US. This means equal trade of kWh in and out of the grid.
        what is the percentage of time you have grid outage?

        also there is a compromise of a hybrid system that has some batteries and is grid tied. Much more efficient than off grid but not as efficient as batteryless grid tie.
        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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        • #5
          Originally posted by georgerc View Post
          Correct me if I am wrong but aren't those systems worthless when the grid is out?
          Plus last I looked into it the poco was buying watts for a fraction of what they sell it to you, but that's not even the main issue, I prefer to have my own stuff and not depend on the grid to come back on after an outage
          If the grid fails to come back on after an outage then you have a much bigger problem then not having electricity.

          Depending on how often you lose power can help determine what type of emergency power backup system you use. The cost of a battery system to "fill in" when the grid is down can cost 10 times what a quality generator and propane fuel storage tank will. Also the generator will work day and night while your batteries will rely on the sun to get recharged.

          IMO solar panels and batteries are not a guaranteed (or low cost) emergency power system.

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          • #6
            Honestly if anything it's mostly a personal preference to be self reliant, the build site is out in the country, I'm told the grid is not very reliable, and when the power goes out it will be the last area restored as more populated areas are a priority.

            If I cared at all about a generator, I wouldn't bother with RE whatsoever, they anoy the you know what out of me, some time back, the neighborhood I currently reside in, in the city was out for about a week, the ground was shaking from all the gennys, I like RE for what it is and I prefer my equipment to be useful to me regardless of the grid.

            Having said all that, assuming grid tie equipment is a completely different animal, or is it? What inverters should I look at, I see them available from 12 v on up, 24 and 48 seem to be popular, beyond that it appears to be an odd ball, I don't need much and I plan on reducing my usage even further, coupling it with some wind power too,

            I saw one inverter advertise as a split fase 240 v does that mean it produces 2 x 120v lines? Are most single phase? Looking at available ones for sale not much technical data comes with the price tag

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            • #7
              You need a bymodal system and should only consider 48v battery bank.
              outback makes some nice systems for what you are looking for.
              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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              • #8
                Originally posted by georgerc View Post
                I have not decided on a battery bank voltage, an beeing unfamiliar with these inverters I can't make a choice

                I'm hoping for some recommendations towards a product or another, a battery voltage
                That is super easy to help with. 0 Volt Batteries. You have no need for them. Why do you want to spend $8000 every 5 years for $1000 worth of electricity you would never use?

                See if you used the batteries every day and not connected to the grid, the power will cost you 5 to 10 times more than buying the power from the POCO. If you go the Bimodal aka Hybrid Inverter still requires the large set of batteries you never use, but you still get the fun and privilege of replacing them for $8000 every 5 years. You are going to love that and the new part time job you get with no days off taking care of batteries.

                Here is the part you will really like. Go with the Bimodal system and the Installer will love you because he gets a lot more money, I mean a lot more money like 300% more, they also get to sell you a Generator as it is required for extended outages. And he keeps loving it every 5 years when you buy new batteries. The giving never stops.

                Don;t be a fool, if you want emergency power get a grid tied system with Generator backup and forget batteries. With a Whole House Generator you get to run everything like it never happened, and get to laugh at your neighbors without power or have batteries while they suffer. With a Bimodal you only get to run a few things like the fridge, and some lights. A Grid Tied System with Genny will cost you 1/3 what a battery system wil cost initially and no expensive battery replacement every 5 years. Don't be a fool.

                MSEE, PE

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                • #9
                  OK so a bymodal system means grid tie with battery backup? 48v we're getting somewhere,

                  Let's clear something up, there won't be an installer, or $8000 worth of battery, that is not up for discussion, I am not going for a week worth of battery backup or any of that, all I am aiming for is some basic power a fridge some lights, if I get my way it will be off grid, my demand is not that great and I don have to do laundry at night or run a central AC unit 8 months out of the year etc

                  I'll Google outback and look at some specs, but for the sake of conversation what's involved in a batteryless systems, pannels, grid tie inverter, how much of it?

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                  • #10
                    If you are thinking off grid then I am in agreement with sunking here. On grid, some backup is nice ( and what I have). Don't think any big loads, just things like fridge, lights, internet etc.

                    for batteryless you you need a grid tie inverter like solaredge, SMA, fronius, etc. no batteries, no charge controllers
                    for bimodal you need a bimodal grid tie inverter, batteries, charge controllers, D.C. Fuses, battery monitor, battery box, large D.C. Cables, etc. and
                    emergency panel with backed up loads moved to it.

                    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                    • #11
                      It seems that folks are all enamored about battery/PV systems, and have their enthusiasm dampened either when they find out the time, treasure and hassle involved, not to mention acquiring a new hobby of battery maint. , or after acquisition when. Just walk in with your eyes open and really know what's required and what you're getting into. Many folks opt for a grid tie and a generator. Independence, or the illusion of it, is a great thing, but it ain't cheap and it does take a fair amount of adjustment in lifestyle. Pay your money, take your choice.

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                      • #12
                        So that's the industry standard, pannels inverter grid and done, and when the grid is out all is worthless? You can't run your house not even when the sun is out? What gives? Those grid tie inverters sense the grid power and don't work when there's none?

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                        • #13
                          You might be interested in SMA's grid tie inverters. Properly installed, you could have 2000 W of power available when the grid is down if your panels are capable of supplying it.
                          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                          • #14
                            Originally posted by georgerc View Post
                            So that's the industry standard, pannels inverter grid and done, and when the grid is out all is worthless? You can't run your house not even when the sun is out? What gives? Those grid tie inverters sense the grid power and don't work when there's none?
                            Part of the reason grid tie PV is down when the grid is down safety - so POCO workers don't get zapped by PV systems feeding the grid during an outage.

                            I'd suggest to consider Sensij's advice and also consider a generator. The world and life is full of compromises.

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                            • #15
                              Originally posted by georgerc View Post
                              So that's the industry standard, pannels inverter grid and done, and when the grid is out all is worthless? You can't run your house not even when the sun is out? What gives? Those grid tie inverters sense the grid power and don't work when there's none?
                              Right. Grid tie PV has NOTHING TO DO with backup power. Solar is a terrible backup, most likely
                              to be out when your grid is down. I bought my generator for that decades ago, have used it 4 times.
                              Bruce Roe

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