On October 22, 2020 the EPA finalized the latest guidance on Project Emissions Accounting for Prevention of Significant Deterioration (PSD) and Nonattainment New Source Review (NNSR). In short, the new guidance says that sources can consider emissions reductions in the first step of emissions accounting, which allows them to couple emissions reductions with increases that may be necessary for their process. These reductions can help sources avoid a more complicated permitting process.
It is, however, up to some individual states to decide if they want to follow this guidance. States can decide to use the old guidelines which do not allow for subtraction of emissions reductions in the first step of the process.
For more details on this final action on Project Emissions Accounting, the EPA has a fact sheet and a link to the final rule posted here: https://www.epa.gov/nsr/nsr-regulatory-actions