It should be 1 power drain every two 200 “ticks” for just having it on, and it depends on what you use it for. Power armor can increase the amount of power per turn, and UPS weapons drain an amount (five or something) every shot.
It’s a pretty big power dump, getting or crafting an extra battery mod should be important to you, as well as unloading every extra flashlight, soldering iron, mp3 player, and general electronic you find