The flow meter method uses the measured flow rate together with annual operating hours, a unit conversion factor, and system efficiency to calculate annual steam use. Energy use is then derived from the steam use and the enthalpy difference, adjusted by boiler efficiency.

\begin{equation}\label{eq:steam-reduction-flow-meter-steam} \dot{m}_{steam} = \dot{V}_{meter} \cdot t_{op} \cdot \frac{k_{units}}{\eta_{sys}}\end{equation}

\begin{equation}\label{eq:steam-reduction-flow-meter-energy} E_{use} = \Delta h \cdot \dot{m}_{steam} \cdot \frac{1}{\eta_{boiler}}\end{equation}

Symbols

\(\dot{m}_{steam}\)	Annual steam use \([\unit{ \kg\per\year}]\)
\(\dot{V}_{meter}\)	Flow meter reading \([\unit{ \kg\per\year}]\)
\(t_{op}\)	Annual operating hours \([\unit{ \hour\per\year}]\)
\(k_{units}\)	Quantity multiplier (number of identical units) \([\unit{ \unitless}]\)
\(\eta_{sys}\)	System efficiency \([\unit{ \unitless}]\)
\(E_{use}\)	Annual energy use \([\unit{ \kJ\per\year}]\)
\(\Delta h\)	Enthalpy difference between steam and feedwater \([\unit{ \kJ\per\kg}]\)
\(\eta_{boiler}\)	Boiler efficiency \([\unit{ \unitless}]\)