EC-740 Ro:7,2 V × 2 Ah = 14.4 Wh

X11 idle:
DeviceA
Nexus One0.5
Hub 4 ports0.1
Keyboard0.1
Mouse0.1
USB monitor1.0
Σ1.8
Σ:5 V × 1.8 A = 9 W
Calculated:14.4 Wh / 9 W = 1.6 h
Measured:2.5 h

Watching TV:
DeviceA
Nexus One0.5
Hub 7 ports0.2
DVB-T0.5
Speakers0.5
Σ1.7
Σ:5 V × 1.7 A = 8.5 W
Calculated:14.4 Wh / 8.5 W = 1.7 h
Measured:3.5 h