What uses less power for a mouse, USB dongle or Bluetooth?

I have been spending a lot of time working remotely with my laptop in random locations. And usually just plug my mouse in via the USB dongle. But just curious if there is a noticeable battery difference doing this? Seems like Bluetooth would be better because it's already powering other things anyway.

Edit: seems like it's Bluetooth. Going to have to change my habits. Thanks all.