The commercial sector is part of the so-called diffuse sectors for the purposes of meeting the targets for reducing greenhouse gases which Europe has set as 10% by 2020, Climate and Energy Package. Within the commercial sector, the entire supermarket type establishments have one of the highest rates of energy consumption per square metre in all commercial and industrial sectors. This paper presents for the first time the results of emissions related to energy consumption assessment study for supermarkets in Spain. All consumptions are considered, including lighting, cooling system, heating, ventilating and air conditioning (HVAC), bakery ovens, hot water, plugs and others. The results indicate that the cooling system has the largest contribution to most environmental impacts. For example, the global warming potential (GWP) over the 20-year lifetime of a supermarket is 6 kt of CO2 eq. Around 50% of the GWP is from the cooling system, 30% from lighting, 10% from bakery ovens and 8% from HVAC. The measures proposed leads to an overall reduction of the impacts. For instance, the GWP reduces by 44% for the cooling system, by 44% for the lighting, by 11% for the HVAC and by 1% for bakery ovens. The results also highlight that these actions have an amortization period of four years and applied to 50% of large Spanish supermarkets would allow to obtain a 14% annually of the need to reduce GHG emissions generated by diffuse sectors of Spain (258,832 ktCO2/year), agreed in “Objective 20-20-20” by the member states of the European Union by the year 2020.