Off Grid Home Forums Technical Discussion Power Usage

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    If I have a windmill or solar panels providing power from my home but I am still connected to the grid how can I know and or decide how much power I receive from each source. Does anyone know how this works?


    There exist sophisticated electronic load balancing systems that handle these sort of power management functions. In essence, they can bring in power from whatever source is available to meet the demand your home is placing on it. They can even decide which is most efficient, based on solar intensity, current wind speeds, etc. If you are in an area with net metering and can sell excess power BACK to the grid, they can handle that, too. They come with a steep price tag still, but they exist. The lowest cost residential systems of this nature that I’ve seen are still over US$10,000.


    Hereis a post from Alt tech site

    Here is an attempt at the whole house off-grid needs.

    My usage has traditionally run at about 1200kwh per month.

    Thats about 40 kwh per day.

    To cover this usage, I would need to consider roghly this:

    Solar Panels / PV:

    an example: 170w panels over 4 net hours of peak performance = 680 watt hours 40000/680 = 59 panels needed!

    so, 60 panels at about 800$ each = 48,000$ !!!

    Batteries :

    an example: 100ah 12v = 1200 watt hours deliverable max at full discharge

    To stay in the top 20% ( for longevity and give a couple of days when sun is poor ) = 1200*.2 = 240 watt hours per battery

    40000/240 = 167 batteries needed !

    so, 168 batteries at 200$ each = 33,000$ !!!


    re calculations on batteries, not quite correct – any off-grid living system should be on 2 volt cells (deep cycle) (always check the cyclic capacity as this will give an indication of the life). Discharge ideally down to 50% depth of discharge (dod)any lower than 80% will kill the battery. After installing these for last 10 years, there is no average system, but based on lifestyle and usage size can vary between 24v and 48v and 1200Ah to 2000Ah. Using 12v monoblocs (leisure batteries, car batteries, truck batteries) etc on any domestic installation with a large inverter can be false economy.

    Nick Rosen

    my freinds and i have designed an electric generation systim which runs on fresh air and have found only brick walls in our attempts to make it feasable for general use . if you or any member has any ideas for us to move on i would be gratefull , all corespondance to my email ….

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