Regardless of the measurement method used to determine annual energy use, the annual energy cost is obtained by multiplying the energy use by the cost per kilowatt-hour. This formula applies uniformly to the multimeter, nameplate, power meter, and other methods.

\begin{equation}\label{eq:electricity-reduction-energy-cost} C_{elec} = r_{elec} \cdot E\end{equation}

Symbols

\(C_{elec}\)	Annual energy cost \([\unit{ \dollar\per\year}]\)
\(r_{elec}\)	Electricity cost rate \([\unit{ \dollar\per\kilo\watt\hour}]\)
\(E\)	Annual energy use \([\unit{ \kilo\watt\hour\per\year}]\)