Exactly How Much Power Is Drained By Registering A Broadcast Receiver For Action_battery_changed?

I am planning to write an app whose sole purpose will be to monitor the battery level, and launch an intent the moment it drops below a certain level. My one concern is that this

Solution 1:

I don't think you'll drain much power. This broadcast is sent only when level changes by one percent,

For example: 85% -> 86% or 76% -> 75%.

Android OS already tracks battery level (it has to track it in order to shutdown phone when level becomes too low, ~3-5%). So just subscribing to this broadcast shouldn't even be noticeable to the user (in terms of battery performance).