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“”My home is all electric. The electric bill runs $200 to $250/month (less in the spring and fall when we aren’t using heat or ac)
The interest on $70,000 at 6% is $350/month.

So, it’s costing the guy at least $100 more per month for electricity, plus he’s out $70,000.””

There is something else that the guy has to concern himself with...maintenance/replacement on the deep-discharge batteries needed to make solar viable. The sun only shines about 12 hours a day. When it sets, solar panels don’t create electricity. The way most systems handle this is to install deep-discharge batteries which charge up during the day and provide electric at night. The problem is that deep-discharge batteries are expensive and don’t last more than ten years.

I suspect that $15,000-$20,000 of the $70,000 he originally invested was for the deep-discharge batteries. That means he will have to invest the same amount (more with inflation) in about ten years to keep his system operational. One thing I don’t know is what the disposal charge is for spent deep-discharge batteries...but I don’t think its cheap.

Keep in mind, he paid $70k in 2001. The price for these types of systems has come down a lot since then. Plus the tax credits are there to reduce your real cost by around 33%. Also, he is probably getting paid by the local utility for extra energy being used.

I do not expect the price of those type batteries to increase in 10 years. Most likely, as solar power becomes cheaper and cheaper, and regular electricity becomes higher and higher, more people will be buying these systems and prices will come down as technology continues to improve.

He is selling current back to the grid, so he is on the grid, unlikely to have a battery bank. The $70K investment sounds high - my ex has 48 panels on her roof, claims to have spent only $20k or so - and sells $100 of power back to the grid each month. No batteries. Not a bad ROI. I'm tempted, particularly knowing that electric is only likely to go higher in future. But I'd have to verify her figures.

She did it cause she thought that this would be helpful for AGW - I tease her that any capture of solar energy contributes to AGW, ha!

Unless you’re trying to live out in the far hinterlands or setting up a survivalist self-sufficiency system, you don’t need batteries — it’s simpler to just sell surplus power to the grid during the day and tap the grid at night.