Mooney M20 pilot reported loss of electrical power due to a generator failure during cruise. Pilot was able to continue to destination airport and land safely.

Narrative

While flying at night on a flight from ZZZ to ZZZ1 (my home airport); I experienced an in-flight power failure leading to loss of radios; transponder; and GPS. I first started to notice a problem when ZZZ Approach asked me to verify my altitude. I reported I was level at 7000 ft; and confirmed the provided altimeter reading. They informed me that my transponder was reporting 8000 ft not 7000 ft; which I confirmed on the transponder display. I also verified my primary and backup altimeter; both reading 7000ft; and my GPS altitude; and reported that I suspected an issue with the transponder. They then handed me off to ZZZ1 Approach and said they were aware of the situation. I cycled the transponder; and suspected electrical noise; so I shut off my anti-collision strobes. This solved the issue for a while so I suspected an issue with the transponder or the altitude encoder. As I continued the flight over ZZZ2; the transponder issue returned; and ZZZ1 Approach requested I turn off Mode C reporting; which I did. I did not suspect a wider electrical issue at this time given that the issue seemed to be isolated to the transponder. I also noticed that the ammeter needle was not moving (in my aircraft; this indicates no current flowing from the generator); but at the time I assumed it meant that the generator had charged the battery enough to no longer be needed. With about 25 minutes remaining in the flight; my transponder shut off entirely and I could not restart it. Now suspecting that I was running my battery down with no generator; I began my load shedding checklist. This included pulling the circuit breakers on my two GI-275 primary flight instruments so they would use only their internal backup batteries; each of which would last 60 minutes. I prioritized the last of my battery power to lower the electric gear and allow any final radio transmissions when I reached my destination. My decision to continue the flight instead of land immediately in ZZZ2 was governed by the relative congestion I observed in the ZZZ2 area; an airport in class C airspace; and my lack of local knowledge as to navigating to airports in the area. I knew that even if I lost all my instruments; and my foreflight iPad; I would still be able to navigate by following roads to any area airport; and had better familiarity with traffic separation normally used by ATC in that area. In addition; despite the relative emergence of the situation; I opted to continue to my clearance limit in accordance with standard NORDO IFR procedures. I was able to reach ZZZ Center by cell phone briefly; who heard my intentions and gave me the number for ZZZ2 Approach. I performed a normal descent to the ZZZ area in a similar fashion to previous flights from the west. I was able to locate ZZZ's airport beacon but found the runway to be unlit. I did not have enough power to transmit on the radio and turn the lights on; and the FBO was closed at the time. I was able to lower the electric gear and confirm that it was down and locked. Now able to reach ZZZ2 Approach by cell phone; the controller tried activating the lights from his transmitter but was unsuccessful. I asked if he could relay the request; and he was able to enlist the help of an airliner overflying the area; which was successful. I landed safely at ZZZ1. Had I not been able to activate the lights; I would have had to fly direct to ZZZ3 and land there; given that my primary instruments now only had 30 minutes of remaining power and I did not want to incur the increased workload of using the backup unlit 'steam gauges.' Overall; I learned the importance of seeing the early signs of an electrical failure; and making sure to correctly interpret abnormal behavior using sound systems knowledge. I was also eager to get home at that late hour; but after debriefing with a CFI friend; we both believe that the decision to continue was reasonable given the factors above and the conditions in the cockpit at the time.