Does L293D consume power when not in use
Yes, it does. Look at the datasheet for the details. Quiescent Current is the spec you want to look at. It draws significant current from Vs as well as from Vss, even when Ven = L. (~30mA max), although it's important to consider the voltages. The 24mA(max) from the 5V rail (Iss) is 120mW, but the 4mA(max) from the 24V rail (Is) is almost as much power (96mW).