In article , Joseph Meehan wrote:
I remember one college project was to figure out how long you needed to
turn out a standard the old 4 foot tubes before you would save money.
Factoring in the cost of electricity lamps and the labor for maintenance to
replace them, it turned out to be about 20 minutes. We had a fun statistics
class back 35 years ago. The CF's would be far less. That start up surge
is like 1/30 of a second and is about 10 times or less of the rated lamp
consumption.

I remember doing calculations on 4-footers of 32-40 watt range also.

One more thing: There are older figures going around as to life lost
per start that date back to 1970's-1950's, and/or are based on "glow
switch" starters (which typically blink the lamp a few times before
getting it on to stay on). 4-footers since the early 1970's at least
have mostly not needed glow switch starters, due to use of ballasts that
have starting means.

It appears to me now that a 4-footer can gain savings by being turned
off for as little as a minute in comparison to being left on. It
appears to me that this explains why I have seen a few instances of motion
sensor switches to turn off the lights in rooms illuminated by 4-footers
if nobody is there - even in a government building restroom!

As for CFLs - they cost more than 4-footers and consume less power than
4-footers, as well as not being as durable as 4-footers! Therefore CFLs
often are better being left on rather than being turned off and back on 5
maybe 10 minutes later, while 4-footers are more in the category of turn
'em off when you leave the room!

As for effects of labor costs - I still see it being worth turning off
4-footers if they will probably stay off for at least 3 minutes, and CFLs
if they will stay off at least 10-36 minutes or so (depending on CFL type
and wattage, electricity cost rate, and labor cost).

- Don Klipstein )