Ledenergy Savings Calculator

A lamp retrofit produces two savings streams and this model prices both: electricity, from the wattage difference times lamp count, annual burn hours and tariff; and avoided replacement hardware and labor, from burn hours divided by rated lamp life. The wattage gap comes from luminous efficacy, roughly 14 lumens per watt for incandescent, 18 for halogen, 60 for compact fluorescent and 90 or more for a current LED, so an 800-lumen output needs about 57 W, 44 W, 13 W or 9 W respectively. Rated lives diverge even more sharply: 1,000 hours for incandescent, 2,000 for halogen, 8,000 for CFL and 25,000 for a household LED. Payback on an incandescent replacement at 3 dollars per lamp and 5 hours of daily use is typically under six months, while a CFL replacement is far weaker at 12 to 24 months because the efficacy gain is only 30 to 40 percent. The emissions figure applies the EPA national average of about 0.417 kg of carbon dioxide per kWh and converts to tree-years at roughly 21.8 kg per urban tree, averages that misstate results on unusually coal-heavy or hydro-heavy grids. Two caveats matter. LED life ratings are L70 figures, the point at which output has fallen to 70 percent of initial lumens rather than the point of failure, and heat shortens them, so an unventilated enclosed fixture can cut rated life by a third. There is also a heat-replacement effect: waste heat from incandescent lamps displaced furnace output in winter, so net cold-season savings are smaller than the electricity math suggests.

Electric lighting spent its first century as a heat engine that happened to glow. Carbon-filament lamps of the 1880s and the tungsten filament introduced in the first decade of the twentieth century converted only a few percent of input power into visible light, and efficacy then barely moved for eighty years. The alternative path began in 1962, when Nick Holonyak Jr., working at General Electric, demonstrated the first practical visible-spectrum light emitting diode, emitting red. Such devices stayed confined to indicators for decades because white light was unreachable. That barrier fell when Shuji Nakamura at Nichia developed a high-brightness blue indium gallium nitride LED in 1993; coating a blue die with yellow phosphor produced white, and Isamu Akasaki, Hiroshi Amano and Nakamura shared the 2014 Nobel Prize in Physics for the underlying nitride work. Commercial displacement was driven by regulation and cost curves together. The Energy Independence and Security Act of 2007 set efficiency requirements for general service lamps that phased in from 2012 and that ordinary incandescent bulbs could not meet, and the Department of Energy backstop requiring roughly 45 lumens per watt took effect in 2023. The DOE also ran an L Prize competition, announced in 2008, pushing manufacturers toward a genuinely equivalent 60-watt replacement. Prices then collapsed as production scaled, from around 40 dollars for an LED A-lamp in 2010 to 2 to 4 dollars within a decade, moving the payback period here from years to months.