0. THE BINDING CONSTRAINT — READ THIS FIRST

After pushing the design to its limit, power is the ceiling. Everything else — compute, storage, decode, network — scales fine. Energy is where physics says no. The whole system is therefore designed in tiers matched to available power, not maximum capability.

rev. 3 re-baseline: the Z440 is shelved and the brain is the ~80W OptiPlex, so the awake load is ~100–120W (not the ~350–400W this section originally assumed), and Phase 1 does no 24/7 parked recording at all — the OptiPlex hibernates parked (~2–5W) and only the ESP32 layer stays on. The "8-camera 24/7" wall below is the worst-case ceiling the design deliberately avoids, retained to show why the tiers exist — it is not the Phase-1 operating point.

THE WALL WE DESIGN AROUND (worst case, deliberately not run in Phase 1):
8-camera 24/7 recording = ~58W = ~116 Ah/day @ 12V
→ no truck battery sustains that for weeks without charging
→ so Phase 1 does NOT attempt 24/7 parked recording at all

THE DESIGN-DOWN ANSWER:
├── DRIVING → alternator + DC-DC powers everything (OptiPlex awake, cams, NVR, LLM) ≈ 100–120W
├── SHORT PARK → house battery buffers the awake system; or OptiPlex hibernates (~2–5W)
├── LONG PARK → OptiPlex hibernates; ESP32 layer (~2–5W) watches + WOL-wakes on alert
└── Footage library builds from drives + awake parks, not 24/7 parked recording
   [ Pi 5 + Hailo-8L, ~1yr out, closes the parked-recording gap as an always-on cam appliance ]

Every tier below is sized against this reality.