Lighting Cost Calculator

In 2026, a homeowner with 67 sockets and a $487 PG&E bill needs to know whether the marginal LED retrofit dollar is better spent in the kitchen (6 high-use sockets) or the bedrooms (lower hours). Static online calculators showing total kWh do not answer this; this tool shows the dollars per ROOM so the retrofit budget hits the highest-ROI sockets first.

The history of artificial lighting starts on 22 October 1879 when Thomas Edison demonstrated a 13.5-hour carbon-filament lamp at Menlo Park, New Jersey. Joseph Swan in the UK had run a similar lamp earlier in February 1879 — both men's patents merged into the Edison & Swan United Electric Light Company in 1883. Tungsten-filament lamps (William Coolidge, GE, 1908) replaced carbon and gave the modern incandescent its 1000-hour life at ~15 lm/W efficacy that persisted essentially unchanged for 100 years.

Fluorescent lighting arrived commercially in 1938 with GE's F-tube products at the New York World's Fair, hitting ~70 lm/W — five times incandescent. Compact fluorescents (CFL) shrunk that to a screw-base lamp via Philips' SL prototype in 1980 and General Electric's commercial Energy Smart in 1995, finally reaching mass adoption after the 2007 Energy Independence and Security Act (EISA) made the 60W incandescent functionally obsolete via efficacy requirements.

The LED revolution that powers this tool's savings math began in 1962 when Nick Holonyak Jr. at General Electric demonstrated the first practical visible-light LED (red GaAsP at 1.9 lm/W — useless for general lighting). Shuji Nakamura at Nichia invented the blue InGaN LED in 1993, which combined with a yellow phosphor created the first white LED in 1996. The Department of Energy's Solid-State Lighting program, established under the Energy Policy Act of 2005, set targets that drove efficacy from 25 lm/W (2005) to 130 lm/W (2024) commercial, with research devices over 250 lm/W.

The price collapse that made all-LED retrofits economic was equally dramatic. Cree's LRP-38 in 2009 launched at $50; by 2014 Cree had shipped a sub-$10 60W-equivalent LED at Home Depot. By 2026 a 9W A19 800-lumen LED retails for $1.50-$3.00 (3-pack), and Philips' Master Connect commercial line ships at $2 each in bulk. The DOE's 2022 Solid-State Lighting Forecast projects 90% of US sockets will be LED by 2035, saving 569 TWh/year — roughly the entire annual generation of the Pacific region.

Regulation has tracked the technology. The 2007 EISA set a phased efficacy floor; the 2009 EU EC 244/2009 banned 100W incandescent; California's Title 24 has tightened LED-only rules since 2020. The DOE's August 2023 final rule sets the federal minimum efficacy at 45 lm/W (general-purpose) effectively excluding incandescent and most halogen. The IEEE 1789-2015 standard on LED flicker, the IES TM-30-20 color-rendering method, and the IEC 62717 LED-module standard together define what a quality LED lamp must achieve.

The lighting-cost calculation in this tool deliberately uses 365 days × hours/day rather than a more sophisticated occupancy model because residential lighting is dominated by predictable evening peaks (17:00-22:00 in winter, 19:00-22:00 in summer) that average out to consistent daily hours per room. Commercial spaces use IES Recommended Practice RP-1 occupancy schedules instead; for a kitchen or bedroom, the simple multiplication is within 10% of metered reality. The DOE Lighting Market Characterization Study 2020 validates the 4-5 h/day default this tool uses for high-use rooms.