the inverter or converter is what's gonna cost you. if you run electricity out to the barn, use the thickest gauge wire you can, throw a phone line in there, water line etc. so you can have 220 in the barn. i will do this to my barn at some point, but my roofline runs north south, so that's kind of annoying. i was actually thinking of using the panels as a shade for one side of the barn. the parking lot at the sacramento state fair uses the solar panels as shades in the parking lot. kind of a neat idea. also, investigate the lifespan of the panels and replacement cost. the degrade slowly over time, so spend the money on the inverter and consider the panels somewhat "disposable". i haven't done it because it's still an economic loser, even with subsidies. i personally wouldn't put them where i would need to repair or replace something like a roof, which is why i like using them as shade panels on the south side of structures. then the rain drips off them, hail can damage them. i installed a french drain on the south side of the house which is uphill to account for this when i eventually do solar.