Lighting Calculations

Choose a lighting calculation according to whether you need light output, electrical demand or operating cost. Lumens describe luminous flux; watts describe electrical input. Comparing the two requires luminous efficacy rather than a universal conversion factor. For an LED replacement, check the required light distribution and light level as well as the input power of the complete fitting, including its driver or ballast. Estimate energy use from quantity, watts and operating hours, then apply your own electricity tariff. A payback calculation also needs purchase and installation cost and explicitly stated assumptions about maintenance or incentives. The LED savings guide explains this comparison and links to the appliance inventory for editable energy-cost scenarios. The calculations below support planning; equal wattage does not establish equivalent lighting performance.