Directive 2013/35/EU of the European Parliament and Council recommends the weighted peak method for assessing non-thermal effects of low frequency (LF) electric and magnetic fields. This article shows that this method is very practical and user friendly and is absolutely reliable to lead to correct results when applied in the time domain. The method can be used without limitations for any field profile and emulates the underlying physical and biological effects significantly better than all other presently known methods. For this reason, this method is described and recommended in many technical standards for assessing the non-thermal effects of electromagnetic fields and is recognized by the international scientific community. The disadvantages of competing methods are demonstrated. Some technical aspects of real measurement systems are also examined.