Calculators › Benchmarking, budgets and carbon Required lighting power reduction calculator
Required lighting power reduction
A space-based allowance sums area times the applicable density for each space. Reduction is the positive excess of installed power; the supplied limits are scenario criteria, not a code-version claim.
Units IP (US) SI (metric)
d P = max ( P actual − A 1 × L P D 1 − A 2 × L P D 2 , 0 ) \mathit{dP} = \max\left(P_{\text{actual}} - A_{1} \times \mathrm{LPD}_{1} - A_{2} \times \mathrm{LPD}_{2},\ 0\right) dP = max ( P actual − A 1 × LPD 1 − A 2 × LPD 2 , 0 ) d P = max ( P actual − A 1 × L P D 1 − A 2 × L P D 2 , 0 ) \mathit{dP} = \max\left(P_{\text{actual}} - A_{1} \times \mathrm{LPD}_{1} - A_{2} \times \mathrm{LPD}_{2},\ 0\right) dP = max ( P actual − A 1 × LPD 1 − A 2 × LPD 2 , 0 )
Calculator
Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.
Worked example
Given
P actual P_{\text{actual}} P actual 8,000 W A 1 A_{1} A 1 5,000 ft² L P D 1 \mathrm{LPD}_{1} LPD 1 1 W/ft² A 2 A_{2} A 2 3,000 ft² L P D 2 \mathrm{LPD}_{2} LPD 2 0.5 W/ft² d P = max ( 8000 − 5000 × 1 − 3000 × 0.5 , 0 ) = 1 , 500 \mathit{dP} = \max\left(8000 - 5000 \times 1 - 3000 \times 0.5,\ 0\right) = 1{,}500 dP = max ( 8000 − 5000 × 1 − 3000 × 0.5 , 0 ) = 1 , 500
Given
P actual P_{\text{actual}} P actual 7,000 W A 1 A_{1} A 1 500 m² L P D 1 \mathrm{LPD}_{1} LPD 1 8 W/m² A 2 A_{2} A 2 300 m² L P D 2 \mathrm{LPD}_{2} LPD 2 6 W/m² d P = max ( 7000 − 500 × 8 − 300 × 6 , 0 ) = 1 , 200 \mathit{dP} = \max\left(7000 - 500 \times 8 - 300 \times 6,\ 0\right) = 1{,}200 dP = max ( 7000 − 500 × 8 − 300 × 6 , 0 ) = 1 , 200
Symbols and units
Symbol Meaning Unit
d P \mathit{dP} dP minimum installed lighting power to remove W P actual P_{\text{actual}} P actual installed lighting input within scope W A 1 A_{1} A 1 first eligible space area ft² L P D 1 \mathrm{LPD}_{1} LPD 1 stipulated first-space allowance W/ft² A 2 A_{2} A 2 second eligible space area ft² L P D 2 \mathrm{LPD}_{2} LPD 2 stipulated second-space allowance W/ft²
Symbol Meaning Unit
d P \mathit{dP} dP minimum installed lighting power to remove W P actual P_{\text{actual}} P actual installed lighting input within scope W A 1 A_{1} A 1 first eligible space area m² L P D 1 \mathrm{LPD}_{1} LPD 1 stipulated first-space allowance W/m² A 2 A_{2} A 2 second eligible space area m² L P D 2 \mathrm{LPD}_{2} LPD 2 stipulated second-space allowance W/m²
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