This is a subject I feel very strongly about.
Cruising, especially passage making, without paper charts is very poor seamanship. I have had my electronics fail - both the older electronics (C80 from lightning strike) and new electronics (E80s on corrosion on HSB). Given enough time, yours will too. THey are electronics!
That seems pretty harsh.
I have some friends cruising out of the UK that were in Maine. They were very comfortable with their electronic charting. I think people that are comfortable, don't worry about losing the ships power. They have redundant devices. These folks each had a laptop, a spare(from an upgrade), a small tablet, smart phone with a chart app, onboard Chart plotter and maybe a hand held gps with simple charts.
At any rate, with solar and wind generation onboard, they were covered if something catastrophic happened to the ships wiring.
The gear they had, laptops, smart phone, tablet, isn't too unusual these days. You could find it in a family kitchen.
But for boats that are comfortable with electronic charting as their sole means of navigation, they would not put that trust in one single system or onboard source, they would have several redundant unattached devices.
Not everyone accepts their way, but I know their seamanship is top notch!