How did tungsten-halogen lamps improve electric lighthouse lighting?

Tungsten-halogen lamps significantly improved electric lighthouse lighting by providing greater efficiency and a longer operational life compared to standard incandescent lamps.1

These lamps function by utilizing a halogen gas filling within a quartz bulb. This chemical process allows the halogen to combine with tungsten that has evaporated from the hot filament, redepositing it back onto the filament and thereby extending its lifespan. Furthermore, this cycle prevents the evaporated tungsten from condensing on the bulb's interior, which would otherwise cause the glass to darken and reduce the light output over time. By maintaining a clear bulb and a durable filament, tungsten-halogen lamps offered a more reliable and efficient light source for coastal navigation structures.21