ClueLuma

Net annual retrofit savings calculator

Combine all effects with correct signs before calculating payback.

Snet=Se+Sd+Creplace,old−Creplace,new+ScoolS_{\text{net}} = S_{e} + S_{d} + C_{\text{replace,old}} - C_{\text{replace,new}} + S_{\text{cool}}

Calculator

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

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Worked example

Given

  • SeS_{e} = 7,300 $/yr
  • SdS_{d} = 2,700 $/yr
  • Creplace,old−Creplace,newC_{\text{replace,old}} - C_{\text{replace,new}} = -450 $/yr
  • ScoolS_{\text{cool}} = 1,800 $/yr
Snet=7300+2700+(−450)+1800=11,350S_{\text{net}} = 7300 + 2700 + \left(-450\right) + 1800 = 11{,}350

Symbols and units

SymbolMeaningUnit
SnetS_{\text{net}}net annual savings$/yr
SeS_{e}lighting-energy cost savings$/yr
SdS_{d}demand savings$/yr
Creplace,old−Creplace,newC_{\text{replace,old}} - C_{\text{replace,new}}lamp replacement cost change$/yr
ScoolS_{\text{cool}}cooling-energy savings$/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.