The deskjet 2720e does not consume much power. We noted an average consumption of barely 5 watts in normal use. In standby, our power meter shows 0.8 watts, which is also very little.
The printer is otherwise quite noisy. We noted a maximum of 69 dB and around 45 dB when printing photos. Activating the silent mode helps limit overall noise, but this comes at the cost of printing speed, which increases to 2.6 pages per minute (ppm), compared to 9.1 ppm in normal times. You also have to dig into the settings of the HP Smart software to activate this discreet mode.