power supply load calculator

In electronic access control, calculating your total power supply load is critical for system stability. Power supplies are the heart of your security infrastructure. If a power supply is under-sized or forced to run at 100% capacity continuously, it generates excessive heat, degrades internal components, and will eventually fail—taking your entire security system offline.

The 80% Rule

Industry best practices dictate that a power supply should never operate continuously at more than 80% of its maximum rated output. This 20% safety margin ensures the power supply can handle unexpected current spikes (such as all electric strikes firing simultaneously during an emergency) and prolongs the lifespan of the hardware.

Where To Find Your Amp Draw

If you aren't sure how many amps your specific hardware requires, you can usually locate the exact number in one of three places:

• The Spec Sheet / Manual: Look under the "Electrical Specifications" or "Power Requirements" section of the product manual. You are looking for terms like "Current Draw" or "Operating Current."
• The Device Label: Most magnetic locks, electric strikes, and control boards have a manufacturer sticker directly on the device listing its operating voltage and amperage.
• Converting Milliamps (mA): Many smaller devices (like proximity readers and motion sensors) list their draw in milliamps. You must convert this to Amps before putting it into the calculator. Simply divide the number by 1000 (e.g., 250mA = 0.25 Amps).

How To Use The Calculator

Enter the quantity and the individual amp draw for each type of device on your system. The calculator will automatically sum the load and apply the life-safety buffer to recommend the exact size power supply enclosure you need to purchase.

Distributing The Power

A 10 Amp power supply produces enough raw energy to run an entire multi-door security system, but it cannot be hooked up to a single output terminal. Funneling 10 Amps down a single wire is an extreme fire hazard. To use a high-capacity power supply safely, you must pair it with a Power Distribution Board (e.g., Altronix PD4CB or PD8UL).

PTC vs. Fused Outputs

Distribution boards split the main power source into multiple, individually protected outputs (usually 4, 8, or 16 outputs). This ensures that if one lock shorts out, it only blows the fuse for that specific door, leaving the rest of the building secure.

• Glass Fuses: Traditional protection. If a power surge occurs, the glass fuse blows and physically breaks the circuit. It must be manually replaced by a technician.
• PTC (Auto-Resettable): Modern solid-state protection. A PTC limits current when overheated by a short. Once the fault is removed and the board cools down, the circuit automatically resets without needing replacement parts.