How would an E-ink display work for a calculator? I haven't used them for more than about 20 minutes in my life, but as long as there isn't a lot of lag while t

How would an E-ink display work for a calculator? I haven't used them for more than about 20 minutes in my life, but as long as there isn't a lot of lag while typing, it seems line it'd be a good choice. Much of the time a calculator is glanced at while doing math on paper or sitting idle while waiting for the next input. A 0-energy display would be ideal for this. It'd be interesting to see a breakdown of energy and energy consumption by part on a calculator.