How much EMI noise is on your power lines indeed?  How to assess the levels of noise and its properties when it is obviously bad idea to connect your oscilloscope or a spectrum analyzer directly to your power lines?

Our EMI interface adapters provide a barrier for high mains voltages but good passage for the noise signal so that you can connect your sensitive instrument to power lines for analysis and quantification. We offer adapters for differential ("normal") and common-mode noise.

With your oscilloscope (we recommend a high-speed digital storage scope) you will be able to observe the transient signals on your power lines.  This is often much more beneficial than to use spectrum analyzer because majority of EMI signals on power lines are transient (spikes and alike) which the spectrum analyzer can easily miss.