Nook Tablet: 5.0 volts, 1.9 amps (9.5 watts)
Nook HD: 5.1 volts, 2 amps (10.2 watts)
Nook HD charger should work with both. I've used the Nook Tablet charger on both HD and Tablet and it works fine. However, based on what the other poster posted, it seems it's better to use the Nook HD charger.