Transient surge absorption capability of su percapacitors is practically implemented in a commercial surge protector known as supercapacitor assisted surge absorber (SCASA). It is a low component count high per formance circuit design which utilizes a coupled inductor topology wound to a powdered-iron magnetic core. This paper investigates non-ideal characteristics of the SCASA transformer designed using various air-gapped ferrites such as manually gapped toroids and mass-produced com mercially available EER cores. Emphasis is given to exam ine surge energy losses associated with leakage magnetic field and fringing flux of gapped transformer prototypes. In predicting effects of an air gap in ferrite materials, an analytical approach based on effective-permeance is used with validations based on SCASA inductance properties. Experimental work presented in this paper are carried out using a Noiseken lightning surge simulator adhering to IEC 60038 and IEEE C62.41 standards. In addition, SCASA pro totypes were subjected to surge immunity tests specified by UL-1449 Underwriters’ laboratory procedures, where a 10% reduction of load-voltage was recorded outperforming the present design.