Group-relamping interval threshold calculator

Break-even fraction of rated life is calculated as (L+G)/(L+S). Use the stated system boundary and matching input units.

I_{\text{min}} = \frac{L + G}{L + S}

Calculator

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

Given

I_{\text{min}} = \frac{4 + 2}{4 + 8} = 0.5

Symbol	Meaning	Unit
$I_{\text{min}}$	break-even fraction of rated life	—
$L$	lamp purchase price	$/lamp
$G$	group labor per lamp	$/lamp
$S$	spot labor per lamp	$/lamp

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