The study address minimizing energy consumption in buildings that operate on the demand side of electricity systems in Australia. This interest in demand-side measures extends to the heating, ventilation, and air-conditioning system in buildings as such system represent 50-60% total energy consumption in an average building in Australia. Currently, building thermal performance classified into three classes based on dead-band temperature range in European and ISO standards. As per literature review there is no significant difference in thermal comfort satisfaction percentages in actual buildings operating within these three temperature performance classes. The study quantified possible energy savings for extreme thermal comfort ranges in ISO & European standards for an HVAC system of a typical medium-sized office building in Australia. The energy savings quantified using a standard simulation software package. The simulation exercise used a prototype building which represents a medium-size office building in Australia. Three cities selected for the simulation Melbourne, Sydney and Brisbane representing different climate zones in Australia. The studies revealed energy savings in all the three cities with higher percentage savings for heating than cooling. The study revealed peak demand energy savings when temperature dead band changed from 2k to 4k and from 4k to 6k in all the three cities under steady state conditions. Greenhouse gas emissions increase with energy demand creating climate change issues. Findings indicate C02 savings percentages for Brisbane, Melbourne and Sydney when temperature dead band settings changed from 2k (Class A) to 4 k (Class B). The effectiveness of the above strategies needs to be tested in real commercial buildings in large scale to address the issue of minimizing energy consumption in commercial buildings in Australia.