It is a widely held belief that leaving lights on saves
electricity if one leaves a room for 15 minutes or less. This is
due to the energy spike associated with turning on any kind of
fluorescent or HID (High-Intensity Discharge) lights. According
to the US Department of Energy, turning on a fluorescent light
causes an inrush of power that lasts for 1/20th of a second and
uses under 5 seconds’ worth of electricity. So this disproves
the “15-minute rule” that most people go by, though changing the
name would probably create confusion with the other, very
important “5-second rule.” Though flicking off fluorescent
lights upon leaving a room (for intervals over 5 seconds) is an
energy-saving practice, the energy spike from turning them back
on still significantly degrades the lifespan of the bulb. This
contributes to CFLs rarely living up to their lifespan claims;
they’re not really built to be turned on and off. Thus, it
presents another factor to consider when turning your lights on
and off: How often do you wa