Apple's review process checks for apps that consume excessive CPU, GPU, or network resources relative to their apparent functionality — background processes or polling loops that keep the device awake unnecessarily fall under this.
Frequently caused by a background location or network polling interval set far more aggressively than the feature actually needs.
"Your app consumes an excessive amount of energy, even when running in the background, per guideline 2.4.2. Please optimize your app's power usage."