Assessing the effectiveness of implementing any plan requires estimating costs and profitability to make necessary adjustments for maximizing its benefits. The National Optimization Plan for Shared Boiler Rooms of Natural Gas Consumers was implemented to achieve savings and reduce consumption nationwide. In the city of Arak, this plan was carried out by the Central Province Gas Company for 68 consumers with residential, administrative, and educational usages. In this study, using the International Performance Measurement and Verification Protocol (IPMVP) while accounting for temperature variations and the effects of the COVID-19 pandemic, the natural gas consumption of these consumers was estimated and compared before and after the plan’s implementation. The savings and reduction in consumption were calculated using building thermal load equations as a substitute parameter. The results showed a significant decrease in consumption and cost savings for a considerable percentage of consumers. Additionally, the highest reductions were observed in educational, residential, and administrative consumers, respectively.