First off, I'm in favor of green energy, but if we're going to make a financial argument, we have to look at the whole situation.
The installation costs from the poster herself/himself:
The initial contract cost was about $45,000, BUT - my local electric company was giving $3.50/watt rebate for solar panel installation. I got a 6,000 watt system, so about $20,000 off the top that I didn't have to pay (installation company took the rebate and didn't charge me). I got about $13,000 tax credits back the following year (credit, so I got the actual cash back). Leaving about $12,000 out of pocket. However, when I signed the contract, I made them add a rider that I would get my roof inspected and if the engineer said the roof wouldn't hold the system I could void the contract. The engineer recommended a new roof. When I told the company that, they said they'd pay for a new roof (!) to keep my business. So I got a $5,000 roof plus the panels for $12,000 out of pocket.
So we'll ignore the roof issue and take the lowest cost ($12k) which is after all the rebates and subsidies.
Next the US Energy Information Administration states that:
In 2011, the average annual electricity consumption for a U.S. residential utility customer was 11,280 kWh, an average of 940 kilowatthours (kWh) per month.
Of course we need to know how much energy costs, and fortunately the Bureau of Labor Statistics just released last month that New York households paid 19.3 cents per kWh in May 2013.
All this means is that an average, non-solar panel New York resident is paying roughly $2180/year while our solared-up resident is only paying $72/year. (This makes the big assumption that varying electricity prices and power usage and solar power availability all even out.)
So, this means Tufflaw will pay off her/his investment in (only) five and three-quarter years (before interest and ignoring any additional maintenance costs), though it would have been closer to 21.5 years if she/he hadn't taken advantage of the subsidies, rebates and tax credits.
I'm not saying it's not for the best, I'm just saying this snapshot is just... a snapshot.