# How much life is consumed each time you turn on a fluorescent lamp?

#### How much life is consumed each time you turn on a fluorescent lamp? — BL, San Jose, CA

The starting process erodes the electrodes of a fluorescent tube through a phenomenon called sputtering. A typical fluorescent tube will last about 50,000 hours if left on continuously but only 20,000 hours if it’s turn on for just 3 hours at a time. From that tidbit, I think its fair to say that a fluorescent tube can only start about 10,000 times. If the tube costs \$5, you are spending about 0.005 cents per start. If the electricity to operate that tube costs about 0.2 cents per hour, then turning the tube off for about 1.5 minutes saves the same amount of money in electricity as it costs in tube life when you turn the tube back on. In short, if you turn the lamp off for less than about 1 minute, you’re wasting money. But if you turn it off for more than 10 minutes, you’re saving money. In between, it’s not so clear. There is a myth that turning on a fluorescent lamp consumes a huge amount of electricity so that you shouldn’t turn the lamp off and on. There is simply no basis to that myth.