| RMS Power | Max Current Draw |
|---|
How Much Current Does an Amp Draw?
An amplifier’s current draw depends on its output power, its efficiency, and the voltage feeding it. Divide the RMS power by efficiency and by running voltage to get the maximum amperage it pulls from the electrical system. That number, not the speaker rating, drives your power wire and fuse choices.
Amplifier Class and Efficiency
Class matters because it sets how much input power becomes heat. Class D amplifiers run around 80 percent efficient and draw the least current for a given output, which is why subwoofer amps favor them. Class AB sits near 60 percent, and Class A is far lower, demanding much heavier wiring for the same wattage.
Fuse and Wire Sizing
Size the power wire to carry the maximum draw and place a fuse near the battery to protect that wire from a short. For multiple amplifiers, total their draw to size the main run, then fuse each amp at its own input. Large systems usually need the Big 3 upgrade and a stiffer charging system.
Frequently Asked Questions
Why is real draw lower than the maximum?
Music is dynamic, so an amp only hits full power on peaks. Average draw is often a third of maximum, but wiring still must handle the peaks safely.
What voltage should I enter?
Use the running voltage with the engine on, around 13.8 to 14.4 volts, since that is when the system plays loudest.
Does a bigger fuse give more power?
No. The fuse protects the wire; oversizing it removes that protection without adding output.