You may be able to get back some of the difference by requiring less total power from your utility and thus lowering the power availability part of the electric bill that applies all day and all year. It's also possible to time shift energy from lower cost times to higher cost ones if you can get time of day billing. And then there's solar of course. I wouldn't be surprised that having that 5k in extra benefit from the system tipped the scales for a battery+solar system in a lot of places with a modest cost of capital.