I was wondering if there is any difference in power consumption between regular graphic interface mode and command line shell mode. And if it is what is the difference? Could I use Ubuntu on the battery longer in shell then gui?
Short answer: NO, simply switching to virtual terminal (VT) won't save you power.
Long answer: It depends.
The power consumption of your PC depends on some factors:
It is clear that switching to CLI will change nothing in regards to the first two points. Okay, that is in theory not 100% true, because if the kernel switches the graphics driver (from proprietary to FOSS) when you switch to VT, then the power saving techniques available to the kernel can be different. But this case is largely theoretical, because the open-source drivers have worse power management capabilities than the proprietary ones, and if you are using proprietary drivers you are advised by the manufacturer to turn off driver switching because the proprietary drivers don't handle that well.
So all is decided in the third point. If the load is smaller on your PC when you use the VT than when you use the GUI, then you are saving power (if the OS/hardware support it). But this is only because of YOU using less demanding programs, less features, not because of the switch to VT. You can put a high load on your computer even in VT, you can stress all your hardware there also (even the VGA can be stressed there too with some computation). And on the opposite, you can put minimal load on your PC in a GUI session also.
So to sum up, it is all decided on the programs you use on your PC, and how you use them, not on the switching to VT.