Slow Electricity: The Return of DC Power? (2016)

Original Article ↗ Hacker News Discussion ↗

Interest in bringing low-voltage DC power back into homes is growing as more devices, solar panels, and batteries already operate on DC, but commenters highlight major obstacles such as lack of standards for voltages and plugs, safety issues, and the difficulty of breaking high-current DC circuits. Many argue that while DC makes sense for specific contexts like RVs, boats, telecom racks, and perhaps 48V home sub-systems, AC remains superior for whole-house distribution, especially for high-power appliances. Overall, the consensus is that AC and DC will increasingly coexist, with localized DC networks feeding electronics and lighting while traditional AC infrastructure continues to handle heavy loads and long-distance transmission.

Desire for Domestic DC Wiring & Standards

  • Several commenters want DC wiring in parallel with AC to avoid many AC→DC adapters, especially with local solar and batteries.
  • Major barrier: lack of standards for DC outlets, plug types, and voltages distinct from AC and from each other.
  • Some think using the same nominal voltage as AC plus local DC–DC adapters might be best; others call this impractical without standardized connectors and protections.

Voltage Levels and Use Cases

  • Low-voltage DC (12–48 V) is seen as suitable for lighting, electronics, pumps, small fans, and similar loads.
  • 12 V has a large ecosystem (cars, RVs, boats) but is criticized as “absurd” for whole-house use due to current and cable size; 48 V is often proposed as a sweet spot.
  • High‑power appliances (stoves, washing machines, HVAC, kettles) are widely viewed as incompatible with low‑voltage DC because of cable losses and required conductor size.
  • Some suggest 200–400 V DC distribution for efficiency, but many see severe safety and switching challenges.

Efficiency, Losses, and Converters

  • Many note that switching conversion (AC↔DC, DC↔DC) is already highly efficient; saving one conversion step may not justify new infrastructure.
  • Others argue DC systems can cut inverter idle losses in off‑grid setups, where AC inverters consume nontrivial standby power.
  • There is debate on how much is gained given almost every device still needs DC–DC conversion for its internal voltages.

Safety, Switching, and Code Issues

  • DC arcs are harder to extinguish; DC breakers and switches exist but are more complex, expensive, and sometimes use problematic gases.
  • Using existing grounding or neutral conductors to carry DC is strongly rejected as unsafe and incompatible with protection systems (GFCI/RCD, bonding practices, fault clearing).
  • High‑voltage DC in homes is viewed as more dangerous for shock and fire, though some argue modern protection could manage it; overall feasibility is left unclear.

Hybrid and Existing DC Ecosystems

  • RVs, boats, and telecom racks commonly use DC (often 12 V or 48 V) plus inverters for occasional AC loads, seen as a realistic model for homes.
  • Power over Ethernet (48 V) and USB‑C/USB PD (up to 240 W at 48 V) are cited as de facto low‑power DC standards.
  • Telecom‑style 48 V DC plus standardized “brick” converters is described as a practical, currently available architecture for DC‑centric systems.