11.

“On the small scale: A reverse osmosis water filtration system. It makes the water taste so much better than a single carbon filter, like what you find in a refrigerator. On the big scale: Solar panels. We went as big as possible, and it produces all the power we need with excess being bought by the power company.”

It paid for itself in under five years, significantly increased our home value, and freed up a good chunk of money that was being paid on electricity every month, which allowed us to install central AC and a new furnace!”

—jbdnco

Source: https://www.buzzfeed.com/lizmrichardson/expensive-items-for-home-worth-the-money