FTC Amplifier Power Rating Rule Federal Trade Commission Amplifier Rule (16 CFR Part 432)

What the rule is

16 CFR Part 432 is the Federal Trade Commission's trade regulation rule on power output claims for amplifiers utilized in home entertainment products. The FTC promulgated it in 1974 (39 FR 15387, May 3, 1974) because manufacturers described performance with claims such as "25 Watts" but tested under a variety of conditions that gave different results for the same product, so consumers could not compare brands. Under 432.1 it applies whenever power output, power band or distortion is represented in advertising or sale of sound power amplification equipment made for home entertainment, including component amplifiers, radios, self-powered speakers for computers, multimedia systems and sound systems. Products whose rated output does not exceed 2 watts are exempt. A violation is an unfair or deceptive practice under section 5(a)(1) of the FTC Act.

The standard test conditions

Section 432.3 defines the test. The AC line must be 120 volts RMS at 60 Hz with less than 2 percent total harmonic content (230 volts and 50 Hz for foreign equipment). The amplifier is preconditioned by driving all channels at one-eighth of rated power for one hour with a 1,000 Hz sine wave, in still air at an ambient temperature of at least 77 degrees F (25 degrees C). Tone and loudness-contour controls are preset flat. Any power level from 250 mW up to rated power must then be obtainable at all frequencies in the 20 Hz to 20 kHz power band at no more than 1.0% total harmonic distortion plus noise (THD+N) into 8 ohms, after input signals have been applied at full rated power for at least five minutes. Rated power is the minimum sine wave continuous average power per channel, measured with all associated channels fully driven, and for multichannel equipment the associated channels include at least the left front and right front.

Worked example for a 100 W rating. Into 8 ohms that is 28.3 V RMS and 3.5 A. The 250 mW lower bound is 1.4 V RMS, so the amplifier must hold 1.0% THD+N across a 26 dB power range (10 times the log of 100 / 0.25) at every frequency from 20 Hz to 20 kHz. The 1.0% limit is -40 dB below the signal. Preconditioning is run at 12.5 W per channel for an hour, and the full-power test is run for at least five minutes before measurement.

Labeling and optional ratings

Under 432.2 the rated output must be disclosed clearly and conspicuously, more prominently than any other representation, and labeled "FTC Power Output Rating." It cannot be placed in a footnote or marked with an asterisk. Under 432.4, a manufacturer may add other ratings, such as peak or dynamic power or a rating at another impedance or distortion, only if they are expressed in minimum watts per channel, labeled "This rating was not tested under the FTC standard," and shown less prominently, meaning not bold and not more than two-thirds the height of the FTC rating.

History: from 1974 to the 2024 amendments

The original rule did not set values for impedance, power band or distortion; sellers had to disclose whatever they used. In 2000 (65 FR 81240) the FTC removed the disclosure requirement from media advertising but kept it for brochures and specification sheets. The agency opened a review with an advance notice on December 18, 2020 and received 550 unique comments, all but one favoring keeping the rule. FTC staff found dozens of examples of the same equipment advertised with different power claims. The first proposal set 8 ohms, 20 Hz to 20 kHz and less than 0.1% THD. Commenters said many tube and solid-state amplifiers could not qualify at 0.1%, so a supplemental proposal raised the limit to 1.0% THD+N. The final rule was published on June 12, 2024 (89 FR 49801) and took effect on August 12, 2024. It also formalized 2010 staff guidance that multichannel ratings must fully drive at least the front left and right channels.

What the rule does not require

Audioholics, which lobbied for the rule and then petitioned to reopen it, notes that the final rule does not specify testing with more than two channels driven at once for multichannel amplifiers, and does not mandate 4-ohm ratings. That means a nine-channel receiver's FTC rating may describe only a front pair. For the all-channels case see all channels driven, for the load question see 4 ohm vs 8 ohm rated power, and for the distortion measurement see THD+N. Audioholics also reads the rule as applying to powered speakers, soundbars and subwoofers and as retroactive to products made before the amendment. The FTC's own text says the amendments apply to sellers that make power claims, and the FTC argued that a manufacturer that does not want to follow the standard need not make a claim.

Where it stands

The Consumer Technology Association (CTA) filed a petition on August 20, 2024 asking the FTC to clarify that the 2024 amendments are not retroactive or to amend them; the FTC posted it on October 16, 2024. In a comment dated May 27, 2025, CTA went further and asked the FTC to rescind the 2024 amendments altogether, arguing they added burdens without a record of widespread deception. No published FTC decision on either request was located for this entry, so check the FTC docket before relying on the rule's current form. Meanwhile 432.3 remains the text in the Code of Federal Regulations.

Reading a spec sheet

Look for the words "FTC Power Output Rating" and the three test values. A claim with "continuous," "RMS," 8 ohms, 20 Hz to 20 kHz and a THD+N figure at or below 1.0% fits the standard. A "dynamic," "peak" or "music power" watt number needs the "not tested under the FTC standard" caveat. See continuous vs dynamic power rating for the difference, and use the amplifier power tool to turn a rating into the volume you will actually get.