Do your break-even calculations really take everything into account? Did you factor in installation, storage costs and switches? Does all the equipment have long-term warranties, backed by companies that will likely be around for a while? I've done the math before on a couple homes, using a few sets of assumptions each. Granted, $300/month is quite high, but without looking at the numbers I would still question the benefit. Solar costs around $5/watt without installation, storage, or infrastructure, and I pay $1.20 per year for that same 1-watt from the power company. I'm guessing there is much lower-hanging fruit in getting your total energy consumption down. I'm not a green advocate by any means, but I do love to cut costs. I know off the top of my head that my TV uses 80 watts, my portable AC 750 watts, and my fridge (average) 112 watts. Replacing a single halogen bulb in the living room with a $3 3-way fluorescent saves me about $20/year, and putting all my computer peripherals on a power strip saved me over $100/year. I've found there are ways to cut costs--at least a little--on a lot of things except a couple of the big hitters. Heaters and electric dryers can't really be made more efficient by virtue of what they do; by definition they are 100% inefficient. A gas dryer replacing an electric will pay off a lot sooner than a solar panel will.
How much energy does $300 buy you? I consume ~400 kw-h per month fairly consistently, except for maybe 1 or 2 months in the summer when I run the AC.