What if your paper chart blows overboard? Or your dog ate it (I'm betting on Tom going first on that one)?

If one chooses all electronic charts, then one usually is thinking of reasonable backups. A year's worth of batteries for a handheld GPS only takes a small space. We have two cameras on board with GPS's in them. Solar panels are rarely damaged by lightning and can be hooked directly to a chartplotter with an inexpensive converter. A small Honda generator will run all of the electronics on the boat even if the mains charger is down.

The alternative list is long indeed.

We took a direct lightning strike that destroyed all of our mounted electronics, the mains charging system, our alternators and the batteries. Didn't stop us using electronic charts one bit. We sailed a week without issue.

The only scenarios I can imagine taking out our ability to use electronic navigation are those where we would also lose paper charts.

Mark