This paper presents extraction of information from results of an interlaboratory comparison in testing, which was performed in the scope of the 5th Framework Program—INCOLAB (INitiative and CO-ordination to prepare LABoratories in Newly Associated States for full implementation of the (LVD) Low-Voltage Directive) project. The comparison covers all the requirements of classical proficiency testing, but also adds metrological aspects in order to improve the outcome of such tests, which is new in the field of interlaboratory comparisons in testing of electric safety. The objective was to show differences in methods and measurements in the black test corner (BTC, which is one of the tests required by the LVD directive standards), when performing the conformity assessment. A digital convection oven and a cooker were chosen as representative samples for comparison. Different shapes of samples were used to put forward understanding and application of the standard requirements. Additionally, the temperature artifact was used for comparison of the BTCs of different participating laboratories. All participating laboratories in this intercomparison were requested to follow the basic instructions given in the technical protocol, applying their everyday test procedure. Results showed a few problematic areas in safety testing. The entire intercomparison proved that in general, and for LVD in particular, better specification for BTCs as an example for a complex measuring instrument is required. Additional information about test samples was also obtained. The concern arising is that a product can be placed on the EU market with the conformity assessment activity support of testing laboratories with quite different measurement capabilities.