Buildings are major consumers of energy and the major contributors to the increase in green house gases. In order to reduce the carbon dioxide emissions, it is necessary to investigate effective ways to refurbish existing buildings to meet sustainable contemporary lifestyle. This paper presents a detailed evaluation of occupants’ impact on the energy consumption in a typical 1930s house, built in the campus of the University of Nottingham. The relationships between occupancy and energy usage due to lighting and change of appliances are evaluated before and after their change. This study will help in taking the right decisions in retrofitting old buildings, reducing future costs and increasing occupants’ satisfaction.