Cessna 172 pilot reported experiencing an alternator failure during a reposition flight; resulting in the return to the departure airport where the pilot landed safely.

Narrative

While attempting to contact AFSS to establish VFR flight following to ZZZ I observed the low voltage warning light illuminate. Over the next several minutes the volt meter showed a steady decline in line voltage. Recycling the alternator master switch was unsuccessful. I shut the avionics bus down to conserve remaining battery power since it would be required at ZZZ; a towered airfield. I did not consider this an emergency since conditions were VFR;I was completely familiar with the terrain; enroute weather; and the route to ZZZ; an iPad with Foreflight had four hours of battery charge remaining; and there is little traffic along this route on weekdays. I remained at 11500msl until clearing the adjacent high terrain and then descended below 10000msl to comply with ADS-B rules. Approximately 15 miles from ZZZ (class D) I was able to gain the ATIS via a handheld radio. At 10 miles out I turned one radio and the transponder/ADS-B on; as a precaution squawking 7600; and was able to obtain a landing clearance; landing was uneventful.Alternator failure (4 years old; rebuilt) is suspected and will be investigated further.While supposedly rare this the third electrical failure I have ever experienced and I've learned to always carry a handheld radio as a backup. It is also suggested that ATC facility telephone numbers be part of flight planning (I do this) since in a declared emergency I would not have hesitated to contact the ZZZ Tower for landing clearance via the cell phone.