The current draw will depend on:
• The sampling Rate (higher sampling rate will draw more power),
• The signal you are putting into the device,
• voltage source to the USB (The lower the voltage supply the higher the current draw will be),
• If the device is waiting for a trigger and
• The resolution settings.
Unfortunately we do not know how much this will vary the power draw.
While it would be possible to carry out tests, and work out the power draw, the number of combinations for a single scope model, and the number of models we have in our range, would make this impractical.
But if you can post here or email firstname.lastname@example.org
with the settings you would be looking to use and the signal you would like measure I would be able to test the 5243A (or 5244A).