BLUEMOMENT

It may be less resource-hungry as I suspected, but if I load up all the different sets of charts I have accumulated over the years, it will more than cancel the advantage! ( but I intend to do it just for fun)
Before we all get carried away, just bear in mind the other resource needed - Battery power! - a laptop with a decent screen will gobble greedily as you glide gently along with the engine in 'silent mode', and a laptop with a frugal tiny screen ain't going to be much good for this application.
The best solution I came across was an old IBM thinkpad* which ran from the boats 12volts direct, and had the battery removed.
Unfortunately nowadays they all seem to want more than 18volts, and that means added inverter losses on top of the gobble.
I know you don't leave it on all night, but during the day, it could be equivalent to a fridge running.
* -note : thinkpads were also built to last, unlike some of the modern stuff with weak hinges and fragile keyboards.

_________________
Just because you're paranoid
doesn't mean they're not out to get you.

The pic below might assist comparisons....



BTW, the MemoryMap package was only £30 at SIBS. That gave 2 PC licenses plus a so-far unused smartphone one.