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Thread: Inverter for future solar power

  1. #1
    DIY Junior Member steve2278's Avatar
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    Default Inverter for future solar power

    Hello everyone,

    I'm building a new home and my electrician is coming in next week to wire my entire house, install the breaker box, the disconnect etc. I plan to purchase several solar panels a few years from now with hope of eventually going off the grid, but it seems more cost effective for me to buy and install inverter now since my electrician's going to be there working on the house anyway. I'm assuming the inverter is hard-wired to the breaker box itself?

    I don't know much about electricity, and I really don't have a game plan as to what type of solar panels I'll be buying down the road but it makes more sense to install the inverter now, as its cheaper for me from a labor standpoint.

    I was wondering if someone could recommend a GOOD inverter? I see there's many types. Some are advertised as off the grid inverters, solar power inverters, DC inverters etc. Maybe they all do the same thing? But then again, maybe not?

    I have a 200 amp service and I converted many of my high-energy consuming appliances to propane to reduce my electrical needs. I don't know if that information is helpful for sake of recommending the type of inverter, as it is my understanding there's some energy loss when an inverter is used, so I'd prefer to have something that's very efficient.

    Any recommendation you could make would be greatly appreciated!

    Thanks,
    Steve

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    Unless you know the open circuit amps and voltages that you will be working with buying and installing an inverter now would be a waste of time. The inverter will be size according to the solar array that is installed.

    Planning on going off grid and depending on photovoltaic panels as your sole source of power will be expensive to say the least. In North America there is only 4 hours average of sun a day which means you will need a battery bank to back up the photovoltaic array on those days where the sun can’t do the job.

    Should you decide to go without entertainment such as TV and video games and using all gas appliances including refrigeration you might get by for around $50,000 up front money. If you are planning on big screen TV, surround sound, DVD players, electric refrigerators and the such then double you startup cost.

    Last I heard just for the panels and their installation is going for ~ $10 per watt. If I was planning on going off grid I would plan on everything I used to be DC and no inverter.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Usually, the solar panels charge a battery bank through a controller so the batteries don't get overcharged, then you use the battery bank connected either directly for DC or through an inverter for AC needs. Since charging batteries generally produces H2 gas as a byproduct, they need to be in a ventillated area that doesn't get too cold, as discharged batteries can be split if they freeze, H2 burns and if it builds up, explode, plus, the colder they are, the less power they can produce.

    The best inverters produce a very good approximation of a sinewave. The cheap ones are closer to a square wave. Square waves are VERY noisy electronically and some devices won't work with them well, if at all. So, that limits the type that would be useful for a whole house use.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY scratch-pad engineer leejosepho's Avatar
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    I can see no need to purchase an inverter now, but you might want to have your electrician either install or at least make allowances (room and accessibility) for the switching gear you would need for alternative power. Or, you might have an isolatible (solar-optional via switching gear) subpanel installed with specific circuits you might later power though an inverter attached on a nearby wall (but powered in the normal way for now).
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

  5. #5
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by jwelectric View Post
    Last I heard just for the panels and their installation is going for ~ $10 per watt. If I was planning on going off grid I would plan on everything I used to be DC and no inverter.
    I just learned that panels can be installed for as little as $8 per watt.

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    Plumber jimbo's Avatar
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    The figures I have seen are that you can get about 10 watts per square foot of panel, so you should probably do more planning about where to put several hundred square feet of panels. And of course, to achieve that "American Dream" of 'off the grid' you need to have a conditioned room the size of your garage for the battery bank. Then of course, you need to go to tech. school for several months to learn to be a battery technician, because these systems are not "hands off" and you need to know what you are doing to properly operate and maintain.

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    Jack of all trades DonL's Avatar
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    The wind generators are as cheap as $1 per watt.

    The Battery problems and maintenance have been the biggest downside of solar or wind systems.


    Americans are spoiled with all the Gismos that use electricity.
    Theory only works perfect in a vacuum.

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    Moderator & Master Plumber hj's Avatar
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    There is more to solar powering your house than just installing "an inverter". If you plan to go "off the grid" you need a battery pack for times, such as the evening, when the sun is not shining. You also have to know how "big" an inverter you need. Therefore the prudent thing to do is wiat and buy the panels and inverter together. Besides, when they bid my solar panel set, the inverter was going to be connected to my system through a 2 pole circuit breaker in the panel, which did not take any "prewiring".
    Licensed residential and commercial plumber

  9. #9

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    As someone already mentioned the best thing you can do today is just make sure you have about 6 feet of clear space next to the panel for additional hardware. While I commend you interest in going off grid, the reality is its not realistic in almost all cases. Power plants are incredibly cost efficient even after taking transmission losses into account and you will be unable to beat their price per KWH in an off grid system even if you spread the cost of the system out over 25 years. The reason for this is because todays batteries are horrible. You will likely need a battery pack costing between 5-10 thousand dollars. After investing this the batteries will only last 7 years before requiring replacement and will require a lot of TLC to even make it that far.

    If you are really interested in solar look into a grid tie system. ALL the power from the panels -minus the inverter losses - is fed directly into the electrical grid offsetting your electric bill in real time. Any power you don't consume is pushed out onto the electrical grid running your meter backwards. This is called net metering and I believe it is available in most states now (check with your power company). There are no batteries to buy or maintain. The power grid also acts like a perfect battery incurring a 0% loss when pushing power onto the grid. Try finding a battery charger that is 100% efficient! These systems do eventually pay for themselves over 10-15 years and federal and state tax incentives can help reduce this. It is also possible to add a few batteries to this type of setup to have power for a few lights and maybe the furnace during a power outage without having to invest in an quality battery bank.

    So don't worry about this stuff right now. An average grid tie inverter setup can run upwards of $3000 and they connect to your existing panel thru a double pole breaker so installation even after the fact should be straightforward. Look at this link to get an idea of what a basic system will cost minus the batteries. http://www.wholesalesolar.com/solarp...er-system.html . I would consider this a MINIMUM solar installation.

    Also make sure you understand all the losses in this type of setup before you invest. The real world output of these systems tends to be much much lower that people initially expect.

    -rick

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    Jack of all trades DonL's Avatar
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    In this part of the woods our electric company will install solar panels and complete system if you sign a 10 year contract with them.

    That may be another option if you have a electric provider that does that in your location.

    Personally I do not like a 10 year contract, but if you install solar power you are in it for the long run.
    Theory only works perfect in a vacuum.

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