Plan reliable alarm power for every zone today. Add devices, currents, hours, and margins easily. Get total draw, supply size, and battery guidance instantly.
| Device | Qty | Standby (mA each) | Alarm (mA each) |
|---|---|---|---|
| Control Panel | 1 | 120 | 200 |
| Keypad | 2 | 60 | 80 |
| Motion Detector | 6 | 15 | 20 |
| Siren | 2 | 0 | 750 |
| Communicator | 1 | 40 | 180 |
Current budgeting reduces nuisance troubles and prevents brownouts during peak demand. Panels, modules, and notification appliances can pull significantly different values in standby versus active alarm. Treat current draw as a load schedule: it supports submittals, commissioning, and future expansion planning.
Standby current represents the continuous draw while the system supervises circuits and communications. Alarm current represents the worst-case operating draw when sounders, strobes, or relays energize. This calculator totals each mode using quantity multiplied by per-device specifications, then reports totals in mA and A.
A practical supply size is the total alarm current multiplied by a headroom factor. Headroom covers inrush, line losses, accessory additions, and aging. If field measurements show voltage sag at terminal blocks, increase headroom or use distributed supplies closer to loads. Always confirm supply listings and output limits match the connected circuits.
Battery amp-hours are estimated from standby amps multiplied by standby hours plus alarm amps multiplied by alarm hours. Derating improves realism by accounting for temperature, battery age, and usable capacity. For critical systems, document the assumed runtimes, then verify with code requirements, device manuals, and authority guidance.
Example dataset: 1 panel (120 mA standby, 200 mA alarm), 2 keypads (60/80 mA), 6 motions (15/20 mA), 2 sirens (0/750 mA), 1 communicator (40/180 mA). With 12 V, 24 h standby, 15 min alarm, 25% headroom, and 20% derate: total standby is 370 mA, total alarm is 2.16 A (about 25.9 W), recommended supply is 2.70 A, and estimated battery is 11.30 Ah. Use these values as a baseline, then replace them with manufacturer data for your exact model numbers.
Size from the highest expected alarm current, then add headroom. Standby is mainly used for battery runtime calculations and for checking continuous draw against supply output limits.
Many designs use 20–30% headroom for uncertainty and future devices. Increase headroom if you expect inrush, long cable runs, high ambient temperature, or planned system growth.
Most alarm device datasheets list current in milliamps, making schedules faster and reducing unit conversion errors. The tool converts totals to amps for supply and power calculations.
Use the manufacturer’s worst-case alarm current, or create separate rows for different modes. For synchronized strobes or pulsed loads, choose the highest sustained current rating.
No. It provides a transparent estimate. Always compare the selected standby and alarm durations to the applicable code requirements and verify battery selection against listings and authority expectations.
Enter the voltage of the power bus you are sizing. For mixed systems, calculate each bus separately or include only devices actually powered by that bus to avoid under- or over-sizing.
Measure current in standby and alarm with a meter or clamp suitable for DC, then compare to your schedule. Update headroom or device values if field readings differ from datasheets.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.