Electrical Load Calculator

Electrical Load Calculator

Estimate electrical load, voltage sag risk, and get upgrade recommendations for your car audio system.

Build Loaded from Shared Link
Settings below have been restored from a shared configuration.
Quick Start Presets — pick a starting point, then customize below
🔊Budget Daily
500W Class D · 90A alt · 8 AWG
Flooded battery · Daily music
🎵Mid Build
1,500W Class D · 120A alt · 4 AWG
AGM battery · Daily music
💥Serious Bass
3,000W Class D · 150A alt · 1/0 AWG
AGM battery · Daily music
🏆Competition SPL
5,000W Class D · 250A alt · 1/0 AWG
Lithium · SPL burp
Compare Mode Active
Your baseline is locked. Change inputs to see how upgrades compare.
* Combined RMS power rating of all amplifiers in your system.
W
Class D is most efficient (~80%). Class AB is less efficient (~60%) but sounds different.
Leave blank to use amp class default. Enter a percentage to override.
%
Daily Music averages ~33% of peak draw. SPL Burp averages ~80% (short bursts near full power).
* Your alternator's rated output in amps. Check vehicle specs or alternator label.
A
Alternators produce less current at idle (typically 55-75% of rated output).
65%
40%100%
Current from headlights, ECU, HVAC, fans, etc. 30-45A is typical.
A
AGM handles deep cycling better. Lithium has more usable capacity but needs compatible charging.
Leave blank to use a typical value for your battery type.
Ah
AWG gauge of your main power wire from battery to amplifier.
* Battery to amplifier distance in feet. 12-18ft is typical.
ft
Good: clean crimps, tight terminals. Average: basic crimps. Poor: loose/corroded connections.
V
V
V
V
Efficiency Defaults
Class D: 80% · Class AB: 60% · Other: 70%
Average Draw Factor
Daily Music: 33% of peak · SPL Burp: 80% of peak
Key Formulas
Peak Current = RMS Watts / (Voltage × Efficiency)
Avg Current = Peak Current × Usage Factor
Net Headroom = (Alt × Idle Factor) − Base Load − Avg Current
Wire Drop = Peak Current × (Ω/1000ft × Round Trip ft) × Conn. Multiplier
Power Loss % = 1 − (Predicted V / Running V)
Wire Resistance (Ω/1000ft, copper @ 20°C)
1/0: 0.0983 · 2 AWG: 0.1563 · 4 AWG: 0.2485 · 8 AWG: 0.6282 · 10 AWG: 0.9989
Battery Usable Capacity
Flooded: 30% · AGM: 50% · Lithium (LiFePO4): 70% · Lithium Titanate (LTO): 90%
Connection Quality Multiplier
Good: 1.0× · Average: 1.15× · Poor: 1.35×
⚠ Simplified estimates for planning. Real-world varies by temperature, wire quality, alternator condition, etc. Always consult a qualified installer.

Electrical Load Calculator · Estimates only — consult a qualified installer for system design and safety.

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