Cheaper--Leave light on or turn it off?

Is it cheaper to leave a light on (flouresnt, incandesant) or shut it off and than turn it back on?

Assuming that using less energy == costing less money, here’s what Cecil has to say:

Man, pretty old article there. Mythbusters tested this one back in 2006. Their findings: there is a tiny “surge” when turning lights on, but it’s largely negligible. The amount of energy consumed in this “surge” is roughly equivalent to leaving the light on for less than one second. The only exception was a fluorescent bulb, whose “surge” was equivalent to leaving the light on for a whopping 23 seconds.

So, turn 'em off to save money, unless you’re going to be back in less than a second for incandescents, or less than 23 seconds for fluorescents.

What about the cost of the bulbs themselves since, as I’ve been led to believe, it is the surge that lessens their life?

The “newer” T-8 flourescent tubes are relatively inexpensive ~$1.50-$2.00 each. They last on average over 5 years.
AFAIK the surge doesn’t effect the lifetime of the bulb as much as it does the electronic ballast.

The Mythbusters tested that part, too, but it’s harder to quantify. Yes, cycling bulbs makes them wear out faster, but how much is too much is hard to say. One advantage of LEDs, which are solid state, is that cycling them has very little effect.

How about the wear and tear on the wall switch that is used to turn the light on and off? Doesn’t the increased use of the switch wear it out faster?

That is correct.

Plus add the energy and time spent by the person perfoming the switching action and the wear and tear of his body parts. It would cause him age faster, and to eat more to make up for the lost energy leading to more consumption of food, and if sufficiently large number of people started doing this ‘light switchy’ thingy it could lead to food shortages and global warming and…


I have a power supply that I bought surplus around 30 years ago (a Q Nobatron). I turn it on and off nearly every day, sometimes multiple times. A few months ago, I noticed that it wouldn’t turn on reliably. I replaced the toggle switch, and decided to do a failure analysis on the old switch. The old switch was very well designed - the contacts were a spring-loaded wire, and a metal plate. The wire snapped against the edge of the plate to make the circuit. After 30+ years, the wire had eroded a path through the plate to the point where it would no longer make contact. I figure the Radio Shack toggle switch I replaced it with will only last 20 years…

I deal with this quite frequently in older facilities. It’s curious that I have to replace parts that have functioned perfectly for 80 years with “newer and better” parts that have 2-5 year life expectancy. I guess it shows the quality of workmanship and utalitarian design that seem to have been lost over the years.