Studio Matrx Monthly · Volume 1 · Issue 2 · July 2026
Amogh N P
 In loving memory of Amogh N P — Architect · Designer · Visionary 
Power supply sizing

Access-Control Power Calculator

The lock, not the reader, dominates an access-control system’s power draw — and magnetic locks hold by power, so they pull current every second the door is armed. Enter your doors, lock type, readers and voltage to get the total current, the watts, and the power supply you should specify. Planning figures; runs in your browser.

Lock type
Magnetic (EM) lock0.5 A · holds by power — draws continuously
System voltage
EM locks are usually 12 V — check the spec plate on your device.
0.0 A
Total current draw
0 W
Total power @ 12 V
0.00 A
Per door
Recommended power supply
Use at least a 10 A / 12 V supply
6.0 A load + 25% headroom = 7.5 A minimum
Where the current goes (per door)
  • Magnetic (EM) lock (lock)0.50 A
  • 1 reader (0.1 A each)0.10 A
  • Controller share0.15 A

Planning estimate only — real holding currents vary by model and rise with more readers and auxiliary devices (REX buttons, break-glass, door position sensors). Magnetic locks draw continuously because they hold by power, so they dominate the load; electric strikes and bolts draw mainly at the moment of release. Add margin and confirm each device’s datasheet. The backup battery is sized separately — use the battery-backup calculator below.