Energy Diagnostics

Symptom-based troubleshooting for iOS energy issues. Start with your symptom, follow the decision tree, get the fix.

Symptoms This Diagnoses

Use when you're experiencing:

• App at top of Battery Settings
• Device gets hot during app use
• High background battery drain
• Battery drains faster on cellular than WiFi
• Energy spike during specific action
• "Phone gets hot" user complaints

Example Prompts

• "My app is at the top of Battery Settings"
• "Users say their phone gets hot when using my app"
• "High background battery drain reported"
• "App drains battery more on cellular than WiFi"
• "Energy spikes when user taps this button"
• "How do I diagnose battery drain?"

Diagnostic Workflow

Claude guides you through symptom-based diagnosis:

Symptom 1: App at Top of Battery Settings

Power Profiler reveals which subsystem:

• CPU high → Timer leak or polling loop
• Network high → Batching issue or polling
• GPU high → Animations running when not visible
• Display high → Light backgrounds on OLED

Symptom 2: Device Gets Hot

During specific action:

• Video/camera → Check encoding efficiency
• Scroll/animation → Reduce effects, check frame rate
• Data processing → Move to background, cache results

During normal use:

• Run Power Profiler to identify continuous drain
• Check for infinite loops or runaway recursion

Symptom 3: Background Drain

Check Info.plist background modes:

• Location → Use significant-change, not continuous
• Audio → Deactivate session when not playing
• Fetch → Reasonable earliestBeginDate
• BGTask → Complete tasks promptly

Symptom 4: Cellular-Only Drain

Check URLSession configuration:

• allowsExpensiveNetworkAccess → Set false for non-urgent
• isDiscretionary → Set true for background downloads
• Request patterns → Batch small requests

Quick Diagnostic Checklist

30-Second Check

• Device plugged in? (Power metrics show 0)
• Debug build? (Less optimized)
• Low Power Mode on? (Affects measurements)

5-Minute Check

• Which subsystem dominant? (CPU/GPU/Network/Display)
• Sustained or spiky?
• Foreground or background?

Common Quick Fixes

Finding	Fix	Time
Timer without tolerance	Add .tolerance = 0.1	1 min
VStack with large ForEach	Change to LazyVStack	1 min
Missing stopUpdatingLocation	Add stop call	2 min
No Dark Mode	Add asset variants	30 min

Documentation Scope

This page documents the axiom-energy-diag diagnostic skill—symptom-based troubleshooting Claude uses when you report battery or energy issues.

For optimization patterns: See energy for Power Profiler workflows.

For API reference: See energy-ref for timer, network, and location APIs.

Related

• energy — Energy optimization patterns and workflows
• energy-ref — Complete energy API reference

Resources

WWDC: 2025-226, 2025-227, 2022-10083

Docs: /instruments, /xcode/improving-your-app-s-performance