Operating hours required by a payback limit calculator

Minimum annual operating hours is calculated as (P/T_max − S_fixed)/(ΔP × r_e). Use the stated system boundary and matching input units.

H_{\text{min}} = \frac{\frac{P}{T_{\text{max}}} - S_{\text{fixed}}}{\Delta P \times r_{e}}

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

H_{\text{min}} = \frac{\frac{9000}{3} - 600}{4 \times 0.12} = 5{,}000

Symbol	Meaning	Unit
$H_{\text{min}}$	minimum annual operating hours	h/year
$P$	net installed investment	$
$T_{\text{max}}$	allowed simple payback	year
$S_{\text{fixed}}$	fixed annual maintenance savings	$/year
$\Delta P$	measured electrical demand reduction	kW
$r_{e}$	avoidable energy price	$/kWh

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.