The way to measure this is not by fan speed, it's by power draw. To measure power draw, the most reliable way is to: a) Make sure you can get your machine in a

The way to measure this is not by fan speed, it's by power draw. To measure power draw, the most reliable way is to: a) Make sure you can get your machine in a quiescent state (say, 5 minutes after bootup, all unnecessary background tasks and services are turned off). b) Make sure ambient temperature is the same between runs. c) Hook your computer up to a PDU with power usage monitoring built in. d) Run automated tests, measuring power usage by the machine during the test. The automated part is important, because you want them to be fairly lengthy and also repeatable. e) Compare results before and after. It's important to have a baseline for comparison so you know whether you're making progress or not.