If you use ntfy.sh and don't use instant delivery, ntfy uses Google's FCM for delivery, which is what everyone else does. It doesn't require a foreground service and has no battery impact.
ntfy offers you additional options with instant delivery or the selfhostable server. That requires a server connection and does impact battery a little. On my phone it doesn't show up in the list it's so low, but others have reported more consumption
ntfy offers you additional options with instant delivery or the selfhostable server. That requires a server connection and does impact battery a little. On my phone it doesn't show up in the list it's so low, but others have reported more consumption