Energy Optimization Reference

Complete API reference for iOS energy efficiency. Covers Power Profiler, timer efficiency, network efficiency, location efficiency, background execution, and display/GPU optimization with WWDC code examples.

When to Use This Reference

Use this reference when you need:

• Power Profiler workflow and interpretation
• Timer API patterns for energy efficiency
• Network coalescing and batching APIs
• Location accuracy and monitoring options
• Background execution best practices
• Display and GPU energy optimization

For discipline patterns: See energy for decision trees and workflows.

For symptom-based diagnosis: See energy-diag for troubleshooting.

Example Prompts

Questions you can ask Claude that will draw from this reference:

• "How do I configure DispatchSource timers with proper leeway?"
• "What's the discretionary flag for URLSession and when should I use it?"
• "How do I set up significant-change location monitoring?"
• "What are the background task duration limits?"
• "How do I use MetricKit to monitor energy in production?"
• "What's the difference between continuous and significant-change location?"

What's Covered

Power Profiler Workflow

• Recording traces in Instruments 26
• Interpreting the 5 power impact lanes
• On-device profiling (iOS 26+)
• Comparing implementations

Timer Efficiency

• DispatchSource vs NSTimer
• Leeway configuration for coalescing
• Timer invalidation patterns
• Common timer leaks

Network Efficiency

• Discretionary transfers
• Request batching
• Connection coalescing
• Background URLSession

Location Efficiency

• Accuracy levels and energy impact
• Continuous vs significant-change monitoring
• Deferred location updates
• Region monitoring
• Background location modes

Background Execution

• BGTaskScheduler patterns
• Processing task duration limits
• Refresh task timing
• App refresh budgets

Display/GPU Optimization

• Dark mode battery benefits on OLED
• Animation energy impact
• Blur effect costs
• EDR and brightness

MetricKit Integration

• MXDiagnosticPayload for energy diagnostics
• Production monitoring
• Hang and crash correlation

Key Pattern

Timer with Proper Leeway

// ✅ GOOD — Leeway allows system to coalesce
let source = DispatchSource.makeTimerSource(queue: .main)
source.schedule(
    deadline: .now(),
    repeating: .seconds(30),
    leeway: .seconds(5)  // 5 seconds flexibility
)
source.setEventHandler { [weak self] in
    self?.update()
}
source.resume()

// ❌ BAD — Zero leeway prevents coalescing
source.schedule(deadline: .now(), repeating: .seconds(30), leeway: .never)

Significant-Change Location

// ✅ GOOD — Low power, event-driven
locationManager.startMonitoringSignificantLocationChanges()
// Updates only on significant movement (500m+ or cell tower change)

// ❌ BAD — Continuous GPS drain
locationManager.desiredAccuracy = kCLLocationAccuracyBest
locationManager.startUpdatingLocation()

Discretionary Network Transfer

// ✅ GOOD — System schedules for optimal energy
let config = URLSessionConfiguration.background(withIdentifier: "sync")
config.isDiscretionary = true  // Defer until optimal conditions
config.allowsCellularAccess = false

Documentation Scope

This page documents the axiom-energy-ref reference skill—complete API coverage Claude uses when you need specific energy optimization APIs and patterns.

For discipline patterns: See energy for Power Profiler workflows and decision trees.

For symptom-based diagnosis: See energy-diag for troubleshooting.

Related

• energy — Discipline skill with Power Profiler workflows
• energy-diag — Symptom-based troubleshooting

Resources

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

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