Verified answer

In order to find the true RMS/wattage of your amp when installed, you need to do these things:

First, you need to get a voltage meter. You can find one that plugs into a cigarette lighter on ebay for like $5-$20, and surprisingly they're pretty accurate. However, they might be off by a .1 or .2 volts.

This involves some basic proportion math.

Now, look at the CEA Certified amp. Let's say your amp is 1000 RMS @ 14.4V

You go to your car, and plug in your voltage meter. Let your car run for about 30 seconds, and take the average of the readings. Lets say the average reading was 13.8V.

Next, you're going to set up this equation. (Rated Voltage/RMS=Given Voltage/RMS)

Basically, this equation. (14.4)/(1000) = (13.8)/(X)

Let X equal the true wattage at 13.8V.

Cross multiply. 14.4X = 1,000(13.8)

14.4X = 13,800

Then divide 13,800 by 14.4 to get the true wattage.

For a CEA Certified 1,000 RMS @ 14.4V amp, here are the results:

-----> The exact true wattage is... 958.3333RMS @ 13.8V <-----

-----> The exact true wattage is... 895.8333RMS @ 12.9V <-----

Remember, your power fluctuates, you might get a voltage drop down to 12.9V or something. Your amp could go down to 800-900RMS.

If you are confused, just tell me what voltage you are getting, and tell me what amp you have, I'll tell you the exact RMS you will get.

Hope this helped you out! :)