ClueLuma

Annual lamp cost change calculator

A negative annual cost change means lamp-purchase savings.

ΔClamp=Nnew×H×LnewLifenew−Nold×H×LoldLifeold{\Delta C_{\text{lamp}}} = \frac{N_{\text{new}} \times H \times L_{\text{new}}}{\text{Life}_{\text{new}}} - \frac{N_{\text{old}} \times H \times L_{\text{old}}}{\text{Life}_{\text{old}}}

Calculator

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

h
h
lamp
lamp
$/lamp
$/lamp
h/yr
$/yr

Worked example

Given

  • Lifenew\text{Life}_{\text{new}} = 50,000 h
  • Lifeold\text{Life}_{\text{old}} = 20,000 h
  • NnewN_{\text{new}} = 400 lamp
  • NoldN_{\text{old}} = 400 lamp
  • LnewL_{\text{new}} = 9 $/lamp
  • LoldL_{\text{old}} = 4 $/lamp
  • HH = 4,000 h/yr
ΔClamp=400×4000×950,000−400×4000×420,000=−32{\Delta C_{\text{lamp}}} = \frac{400 \times 4000 \times 9}{50{,}000} - \frac{400 \times 4000 \times 4}{20{,}000} = -32

Symbols and units

SymbolMeaningUnit
ΔClamp{\Delta C_{\text{lamp}}}new minus old lamp cost$/yr
Lifenew\text{Life}_{\text{new}}new lamp lifeh
Lifeold\text{Life}_{\text{old}}old lamp lifeh
NnewN_{\text{new}}new lamp countlamp
NoldN_{\text{old}}old lamp countlamp
LnewL_{\text{new}}new lamp price$/lamp
LoldL_{\text{old}}old lamp price$/lamp
HHannual operating hoursh/yr

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