Many facilities use standalone diesel emergency power supply systems (EPSS) to provide energy resilience in the event of a power outage. Diesel engines with on-site fuel storage are traditionally viewed as the most reliable option for standby power; however, these systems have demonstrated vulnerability to fuel deterioration, contamination, and poor maintenance leading to equipment failures. As a result, diesel gensets often do not perform as expected. Advancements in natural gas engines can meet the code-required startup time and power requirements for EPSS and sustain long runtimes beyond two weeks. Natural gas EPSS offer higher reliability, lower maintenance and lower fuel costs compared to diesel systems, yielding lifecycle costs (LCC) savings. In addition to standby operation, a new category of gensets with Environmental Protection Agency (EPA) non-emergency certification can be used for standby and demand-side management (DSM) to provide cost-effective energy resilience for commercial facilities. For facilities with high demand charge rates, natural gas non-emergency gensets can reduce lifecycle costs, offering more affordable energy assurance than emergency-only gensets. This paper will present two case studies of natural gas EPSS with DSM operation to demonstrate the economic benefits compared to both conventional diesel and natural gas emergency-only EPSS.