2nd/10_Wiki/Topics/Frontend/전력 시스템(Power Systems).md

---
id: wiki-2026-0508-전력-시스템-power-systems
title: 전력 시스템 (Power Systems) — 프론트엔드 관점
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Battery API, Power-aware UI, Energy efficiency]
duplicate_of: none
source_trust_level: A
confidence_score: 0.85
verification_status: applied
tags: [frontend, performance, battery, mobile, energy]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: JavaScript
  framework: Web APIs
---

# 전력 시스템 (Power Systems) — 프론트엔드 관점

## 매 한 줄
> **"매 mobile / laptop 의 battery 와 thermal budget 을 의식하는 frontend"**. 2026 매 user 의 80%+ 가 mobile 매 access — 매 60fps 의 X, 매 power-aware design 이 differentiator. Battery API deprecation 후 매 alternative signal (visibility, network, thermal) 활용.

## 매 핵심

### 매 power consumer (frontend)
- **CPU/JS**: 매 long task, 매 layout thrash, 매 polling.
- **GPU**: 매 unnecessary compositing, 매 large canvas, 매 video decode.
- **Network/radio**: 매 frequent fetch, 매 large payload, 매 keep-alive.
- **Display**: 매 bright pixels, 매 high refresh rate.
- **Sensors**: GPS, accelerometer, camera 매 always-on.

### 매 power-aware signals
- **Page Visibility API**: 매 hidden 시 매 work 중단.
- **prefers-reduced-motion**: 매 animation 축소.
- **Network Information API**: 매 'slow-2g' / 'saveData' 감지.
- **deprecated Battery API**: Chrome 84+ removed — 매 indirect signal 의존.

### 매 응용
1. Background tab 매 timer/animation 정지.
2. Save-data mode 매 image/video 축소.
3. requestIdleCallback 매 non-critical work 의 deferral.

## 💻 패턴

### Page Visibility — 매 hidden 시 정지
```javascript
let rafId = null;

function tick() {
  // 매 expensive animation
  draw();
  rafId = requestAnimationFrame(tick);
}

document.addEventListener('visibilitychange', () => {
  if (document.hidden) {
    cancelAnimationFrame(rafId);
    rafId = null;
  } else if (!rafId) {
    rafId = requestAnimationFrame(tick);
  }
});
```

### Save-Data — 매 light mode
```javascript
function getDataSaverMode() {
  const conn = navigator.connection || navigator.mozConnection;
  if (!conn) return false;
  return conn.saveData === true ||
    ['slow-2g', '2g'].includes(conn.effectiveType);
}

if (getDataSaverMode()) {
  document.body.classList.add('lite-mode');
  // 매 disable autoplay video, large hero image, prefetch
}
```

### prefers-reduced-motion
```css
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}
```

```javascript
const mq = window.matchMedia('(prefers-reduced-motion: reduce)');
if (mq.matches) {
  // 매 expensive parallax, particle 매 비활성화
  disableParallax();
}
```

### requestIdleCallback — 매 non-urgent work
```javascript
function scheduleAnalytics(payload) {
  if ('requestIdleCallback' in window) {
    requestIdleCallback(() => sendBeacon(payload), { timeout: 2000 });
  } else {
    setTimeout(() => sendBeacon(payload), 0);
  }
}

function sendBeacon(payload) {
  navigator.sendBeacon('/analytics', JSON.stringify(payload));
}
```

### Intersection Observer — 매 viewport 외 lazy
```javascript
const io = new IntersectionObserver((entries) => {
  for (const e of entries) {
    if (e.isIntersecting) {
      const img = e.target;
      img.src = img.dataset.src;
      io.unobserve(img);
    }
  }
}, { rootMargin: '200px' });

document.querySelectorAll('img[data-src]').forEach((img) => io.observe(img));
```

### 매 throttle WebSocket on hidden
```javascript
class PowerAwareSocket {
  constructor(url) {
    this.url = url;
    this.connect();
    document.addEventListener('visibilitychange', () => this.adjust());
  }
  connect() {
    this.ws = new WebSocket(this.url);
  }
  adjust() {
    if (document.hidden) {
      // 매 hidden — close to save radio
      this.ws.close();
    } else if (this.ws.readyState !== WebSocket.OPEN) {
      this.connect();
    }
  }
}
```

### CSS — 매 dark mode 매 OLED 절전
```css
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000; /* 매 true black 매 OLED 의 pixel off */
    --fg: #e8e8e8;
  }
}
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| 매 background tab | requestAnimationFrame 정지 |
| 매 save-data | image quality 축소, prefetch X |
| 매 reduced-motion | animation 비활성화 |
| 매 idle | requestIdleCallback |
| 매 OLED + dark mode | true black bg |

**기본값**: visibility + saveData + reduced-motion 의 3개 매 mandatory.

## 🔗 Graph
- 부모: [[Web Performance]] · [[Mobile Web]]
- 변형: [[Save-Data]] · [[Reduced Motion]] · [[Dark Mode]]
- 응용: [[PWA]] · [[Mobile UX]]
- Adjacent: [[Page Visibility API]] · [[Network Information API]]

## 🤖 LLM 활용
**언제**: 매 power profile audit, 매 power-aware UX 추천.
**언제 X**: 매 actual battery measurement (impossible from JS).

## ❌ 안티패턴
- **항상 60fps animation**: 매 background tab 도 — 매 battery drain.
- **polling 5s**: 매 mobile radio 매 always-on — push 또는 long-poll.
- **autoplay video 4K**: 매 cellular 매 data + battery.

## 🧪 검증 / 중복
- Verified (MDN Page Visibility, Network Information, Web.dev power).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — power-aware frontend, visibility/saveData/reduced-motion 패턴 |