Consistent operation of adaptive optics (AOs) systems requires the use of a wavefront sensor (WFS) with high sensitivity and low noise. The nonlinear curvature WFS (nlCWFS) has been shown both in simulations and lab experiments to be more sensitive than the industry-standard Shack–Hartmann WFS (SHWFS), but its noise characteristics have yet to be thoroughly explored. In this work, we develop a spatial domain wavefront error budget for the nlCWFS that includes common sources of noise that introduce uncertainty into the reconstruction process (photon noise, finite bit depth, read noise, vibrations, non-common-path errors, servo lag, etc.). We find that the nlCWFS can outperform the SHWFS in a variety of environmental conditions and that the primary challenge involves overcoming speed limitations related to the wavefront reconstructor. The results of this work may be used to inform the design of nlCWFS systems for a broad range of AO applications.