Power draw will be a bit higher than what you're used to for LED displays but not excessive, < 10 mA, they start to light up around 90V iirc, lifespan in the 100's of thousands of hours for the newest ones.
Can you recommend a good cost-effective kit/clock for someone to dip their toes into the field with? I've often looked at them, but when forking over a couple of hundred US dollars, a bit of insight into what's what would be ideal :P