We always aim to keep our tools well-optimized and resource-efficient, and the current implementation of the in-app tracking filter is expected to have minimal impact on the battery life.
It's okay to see a high background time attributed to 1Blocker while reviewing your device's battery usage in iOS Settings > Battery because the filter works via a local VPN profile. If a VPN profile is enabled, it's considered active by iOS.
The battery usage rate may sometimes be higher than usual if the in-app filter actively blocks tracking requests because each request goes through 1Blocker's VPN profile.
In this case, it's worth setting this tool to the DNS Proxy mode in the (…) menu of the Block In-App Trackers section. 1Blocker may take about one minute to reconfigure the filtering mode.