The total annual cost is the simple sum of the loaded and unloaded components. This value represents the baseline against which energy efficiency improvements (VSD drives, pressure setpoint optimization, compressor staging) can be compared.

\begin{equation}\label{eq:operating-cost-total} C_{total} = C_{loaded} + C_{unloaded} \end{equation}

Symbols

\(C_{total}\)	Total annual electricity cost \([\unit{ \dollar\per\year}]\)
\(C_{loaded}\)	Annual electricity cost in the loaded condition \([\unit{ \dollar\per\year}]\)
\(C_{unloaded}\)	Annual electricity cost in the unloaded condition \([\unit{ \dollar\per\year}]\)