Battery anxiety finds a new villain every few years, and right now it's pointed at the eSIM. We tested the actual claims rather than repeating them, which turn out mostly - not entirely - to be nothing.
Myth: an eSIM drains your battery faster than a physical SIM
No measurable difference. Both use the same radio hardware to talk to the same towers; the SIM, physical or embedded, is just where the identity credentials live. It draws no meaningful power of its own, and swapping one for the other changes nothing about your phone's radio behaviour.
If you've noticed your battery behaving differently since switching to eSIM, the more likely explanation is the trip itself - more screen time for maps and translation apps, more photos, more hours away from a charger, not the credential format sitting quietly in the background.
Myth: running two active lines doubles your battery drain
Mostly false, with a real exception worth knowing. Two idle lines sitting on strong signal cost barely more than one. The drain shows up specifically in poor coverage, when either line is actively hunting for a signal it can't find - the same battery cost a single SIM would rack up alone in a dead zone, just potentially from two lines instead of one. The fix isn't disabling the eSIM; it's turning off data roaming on whichever line you're not using in a weak-signal area.
Worth a specific mention: leaving your home SIM searching for a network that doesn't reach where you are is usually the bigger culprit than the travel eSIM. Switching the home line to airplane-style standby, while keeping the local eSIM active for data, often fixes more battery complaints than people expect.