Non-orthogonal multiple access (NOMA) transmission techniques promise reduced latency, massive user deployments, and higher data rates. To investigate how these per-formance enhancements translate to practical deployments in a network, a reliable system-level abstraction for downlink two-user power domain NOMA with successive interference cancellation at the receiver is needed. A simple and efficient abstraction is described and then validated through comparison with link-level simulation results. With the developed abstraction, the effects of the deployment of NOMA techniques in a wireless network with a large number of machine type communication users are evaluated in terms of cell throughput, number of users served simultaneously, and fairness.