During electrical resistance heating (ERH), an electric current is applied to aquifers contaminated with volatile and semi-volatile organic compounds (VOCs and SVOCs). Due to the electrical resistance of the soil, some of the electrical energy converts to heat. As a result, temperature rises and allows volatilization of the compounds once the co-boiling temperature is reached. The process is continued by extracting the resultant gas, remediating the contaminated site. However, this process can be complicated by the existence of clay lenses. Because of their high entry pressure and low permeability, the co-boiling temperature increases considerably which may require extensive periods of heating. In this study, a numerical model, ET-MIP, is used to analyze the mechanism of contaminant removal from clay lenses and the feasibility of contaminant removal through temperature-induced convective flow instead of gas generation in clay lenses. ET-MIP is a MATLAB-based code that combines a conventional continuum approach by solving the governing equations using a finite difference approach for water flow, heat transfer, mass transfer, while gas transport is modelled using macroscopic invasion percolation (MIP), a discrete approach. Parameters studied here are clay permeability, clay entry pressure, target temperature, and groundwater velocity. The scenarios are compared based on their total mass removal, required heating time, and energy efficiency.