The math varies a lot by location. In the US the costs of gear and install are typically higher (twice as high as here.) It'll also obviously be a factor of ele

The math varies a lot by location. In the US the costs of gear and install are typically higher (twice as high as here.) It'll also obviously be a factor of electricity cost, sunny days, your residential consumption and so on. Personally I get 17.5% return on capital spent (and ways to improve that further) so the math works out well. Ymmv.