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Home Forums Technical Discussion Inverter Suggestions for Fully Off-Grid System Re: Inverter Suggestions for Fully Off-Grid System


There are a lot of good since wave inverters available for off-grid use. When picking one, of designing any off-grid power system, everything starts with the load – both the peak load and the average load. I can send you a .xls worksheet that will size a residential system for you if you know your peak sun exposure. Once you know your load and decide your battery system voltage, you can calculate the battery reserve capacity for 24 hours 48 hours, etc. When you have the battery sized, you then can calculate the size of your battery charger – be it solar, hydro, diesel generator, whatever.

Off grid power is battery power unless you’re working with a fairly large microhydro system that can handle peak loading. It’s not a solar powered home, it is a battery powered home.

I am partial to Outback Power Systems, though Magnum makes a nice single box 240VAC unit. Outback requires the use of two inverters at 120VAC to make split phase 240 VAC, or the use of a toroidal transformer if you only need 240 for a well pump occasionally. Exeltech builds good product as well, though I use them mostly for commercial and industrial power systems; at communications sites that don’t require positive ground, mostly.

Life on batteries requires some diligence in design and in lifestyle choices. A 52 inch TV lifestyle with a hot tub – run primarily by a diesel or propane generator – is NOT off-grid at all, since diesel is provided by a very large grid called global oil production and distribution. Global conventional oil production peaked in 2005-2006 per the EIA and IEA and supplies will not be cheap or reliable over the life, or even warranty, of a new solar power system. Mismatched lifestyle to battery to charger designs inevitably lead to premature battery failure, and lead is NOT inexpensive anymore.

Finally, AC charging is highly efficient, since 1. backup generators that produce AC very dirt cheap and 2. off-grid inverter/chargers such as the Outback product can provide the multi-state charging the batteries need while unloading them during recharge by switching all loads to the generator, which minimizes the time the gennie runs (and that you have to listen to it.)