Solar roof on Ioniq 5 and Prius is an option, not standard. And it's rare. In fact, I've never seen it or even heard of it until I looked up what you were saying. And for the Ioniq 5 solar roof, it seems that it's not even offered at all in some countries.

The Prius one is "Offered as an option on the range-topping XSE Premium trim". Far from standard. This roof literally adds up to 4 of miles of range on a good day. (1) So it's a high-end gimmick that has niche use at best on a car, when compared to a fixed solar / battery installation situated where the car is parked.

It won't be any more useful on a boat.

1) https://www.reddit.com/r/electricvehicles/comments/13w5cb1/o...

> It's made out of aluminum instead of steel. The resulting weight savings make it a bit more efficient. That's something this shipping yard specializes in.

According to that person, weight does indeed matter.

There's also the matter of windage and what impacts that might have on the ship.

To say nothing of the capacity factor and reliability of electronics in a marine environment.

Another point with battery powered ships is that the rate at which they discharge is speed dependent and that's a non linear relationship because the drag increases quadratic with speed. So, if you are at 30%, you can still make it across. Just not at the full speed. This is less about range anxiety than it is about just being able to stick to schedules. If the ship did not charge enough it would have to go slower. But it would still get there. This ship is designed to go quite fast which means it would have a lot of wiggle room. So they might make it across at full speed even at maybe a 60% charge. The risk is that they'd run low and might have to slow down a bit. It would get there but with a delay if that happens. And then it would have to sit there a bit longer recharging leading to more delays.

The trick is optimizing the amount of batteries to minimize turnover and delays; not around being able to charge them from 0 to 100%. The sweet spot is probably around the 20-80% mark, meaning you'd want to be able do a crossing at full speed using about 50-60% of the battery capacity. The rest is just there as safety margin to avoid delays. If you burn into that, you need to charge a bit more. With 40-50 minutes turnover, there's plenty of time to do that typically.