What drains the battery of DSLRs the most?

I have found that the battery life of DSLRs is often denoted in terms of possible shots rather than in running time (e.g. according to snapsort, one battery life on a EOS 70D is enough for 920 shots vs. 1100 shots on a 40D). This got me thinking as to what are the main sources of power/battery drainage on DSLRs (specifically, Canon EOS cameras), and what can in turn be done to increase battery life.

So:

1. Apart from taking a picture, what are the functions/actions that drain the battery the most and how do those compare to the power reqired for taking a picture? (I'm especially interested in any setting/function that will have a significant impact on battery life; for example, the image stabilisation function on some ES-F lenses? Continuous focusing using AI Servo AF?)


2. While I'm out taking pictures, is it 'worth it' to turn the camera off in between shots (assuming the intervals will rather be minutes/tens of minutes than hours)? Or is the power consumption while the camera is turned on but not taking pictures negligible?


3. How big an impact does the LCD screen have on the battery life? I assume using the Liveview instead of the Viewfinder continuously will drain the battery faster. However I usually use the Viewfinder and have only the info display turned on (the one where I can access the quick settings). Does this drain the battery considerably as well (i.e. is it wort considering turning it off entirely)?

Answer

LCD screen and any wireless features like Bluetooth, WiFi or GPS would be the heaviest drain. This would be followed by flash/focus-assist then auto-focus, image stabilization would probably be next. Just being on (or even off and providing enough power for the display counts) would be a minor drain. Keeping the camera on between shots won't do too much. IS/VR/OS and AF probably don't drain much as long as you aren't activating the camera's focus. But most dSLRs turn on really quick so if you are trying to get the most out of your battery just shut the camera off when you aren't taking a picture.

To save battery life don't use live preview or video features and turn off the show picture after every shot feature.