Is there a way to view the CPU usage of individual plugins in Sonar?If there isn't does anyone know of a 3rd party utility that would do the job?The CPU meter in Sonar isn't informative enough for me.

"Task Manager > Processes" is the best way in Windows to see how much CPU is being used by each process - however I do not believe that will help you. I'm pretty sure Sonar shows as a single process, and the plugins just load under that process, not as individuals.
 
Sorry, I don't know of any 3rd party app, but someone else might...

The problem is, that the plug-ins are just that: plugged in software extensions. They aren't stand-alone programs, but rather extensions of Sonar. Unless Sonar had a tool or CPU view that could show how its own CPU utilization is being allocated, there's really no way for the OS to see it. The plug-ins act like nothing more than an open file to Sonar, and Sonar reads all the code in that file, interpreting and using it on its own. From how to tailor the audio to meet the spec's of the plug-in, to how to render the plug-in's faceplate, Sonar does all the actual "work". The plug-in is merely code loaded into Sonar.
 
More, it would be way difficult to see this in Waves plug-ins, me thinks, since Waves allows Sonar to load a single WaveShell.dll for using any or all of their plug-ins.
 
My suggestion is this. Get used to Disabling all plug-ins (CTRL+E?), and first see if that drops your CPU usage to almost nothing. Then start re-enabling plug-ins until you see one or more of a same-type of plug-in that dramatically raises the CPU usage. You may toggle the Audio Engine in the Time Window in the Control Bar, to stop anything that may be lingering after disabling the plug-ins. You may also have to Play and Stop the Project to "wake up" the effects of the plug-ins to eat more CPU.
 
What's I've found in the past are older plug-ins, Modeling plug-ins, Convolution Reverbs, or free plug-ins tend to eat up more CPU than well-designed commercial standard EQ's, compressors, or Effects.

Exactly right, it's hard to measure the performance of an accelerator pedal and steering wheel in a car for instance. Plugins are not stand alone units unlike the things they emulate (on the whole). Cheers...

If there are some individual ones you suspect of being CPU heavy (which some are) look at the difference in usage with them switched on or off. This will give you some idea of their impact to the overall usage. If you want to get some idea of the total hit of all the plugins on a given project compare the usage with them running and and with them all bypassed.

Stack 20 of the same plug-ins in a track, disable multi-core, and at least you can get a relative idea of which ones draw more CPU.

The Windows 8 Task Manager does a better job of separating the plugins from Sonar and if you switch plugins back and forth you can tell which ones are using more resources.

No, there is no way to determine the CPU usage of individual plugins except indirectly, by comparing overall usage with and without them, and even that's only a crude approximation.
 
Craig's suggestion is the standard way of doing it. By sticking in a whole bunch of the same plugin, you exaggerate its contribution to overall CPU usage and thereby minimize the relative impact of other variables. Even then, you're still not really measuring CPU usage directly, but rather how much of the available CPU time was being used, which is dependent on a great many factors and can vary from moment to moment.
 
Even if there was some standard test for plugin efficiency, performance would still be variable depending on the plugin's modes, settings and options, and even on the audio data. For example, a compressor performs fewer calculations when the input is below its threshold than when it's above it, a soft knee requires more calculations than a hard knee, and automatic release takes more work than fixed release times. All this might make it impossible to perform a meaningful comparison of two disparate compressors.
 
Sadly, we're stuck with anecdotal evidence for which plugins are lightweight and which ones are CPU hogs.