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 unit of natural gas. This formula applies uniformly to the flow meter, air mass flow, water mass flow, and other methods.

\begin{equation}\label{eq:natural-gas-reduction-energy-cost} C_{energy} = r_{fuel} \cdot Q_{total}\end{equation}

Symbols

\(C_{energy}\)	Annual natural gas energy cost \([\unit{ \dollar\per\year}]\)
\(r_{fuel}\)	Natural gas fuel cost rate \([\unit{ \dollar\per\MMBtu}]\)
\(Q_{total}\)	Annual natural gas energy use \([\unit{ \MMBtu\per\year}]\)