In Australia, after a $2500 .gov subsidy, mine will pay for themselves in 4.5 years. LG Panels with 25 Year output guarantee. 6.6kw System. Financially speaking it's a complete no brainer.
One thing I did notice when I was living in the USA though, was how expensive it was over there compared to Australia. Installation costs are 3x the price, I have no idea why. My system before the subsidy was $11k, and that was for top of the line panels and inverter. Cheap panels would have been around $7k
Electricity costs are ~ $0.2 per kwh, AUD