Turning off the lights in your house can be cost effective, but how cost effective it is will depend on the type of lights that you use. This is important because all light bulbs have a nominal or rated operating life and the operating life is affected by how many times they are turned on and off. The more times that the lights are switched off the lower their operating life, which is affected by how many times it is switched on and off and what kind of light it is.

Incandescent lights or bulbs should be turned off whenever they are not needed. These types of light bulbs are inexpensive to produce and are usually inefficient. Only 10-15% of the electricity that is used by these light bulbs produces light, the rest of the electricity used is turned into heat. If you keep, the lights off the room will be kept cooler, which can be a huge bonus in the summer. With this type of light bulb, the energy saved by turning the lights off when they are not in use will be greater than the cost of having to replace the bulb.

With fluorescent lights the general rule of thumb in the United States is that you should turn them off if you are going to be leaving the room for more than 15 minutes, during peak demand periods or in areas where the electric rates are high you will want to reduce the time to five minutes. Fluorescent lights are more expensive to buy and their life span is affected by the number of times that you turn the light on and off, so it is a trade-off between saving energy and money by turning the lights off frequently and having to replace the fluorescent light bulbs more frequently. The main reason that you do not want to turn fluorescent lights on and off is that it takes a lot of energy to get started, so if you are only going to be leaving the room for a few seconds it is best just to leave the light on. When turning on the light there is an increase in power demand, how much is needed will depend on the type of ballast and lamp.

To figure out how much you will save by turning a light off you are going to need to determine how much energy the light uses when it is turned on. To do this you will need to find the Watt rating that is printed on the light bulb and determine how many Watts it is using during the time that it is on. For example, if the rating is 60 watts and you have the light bulb on for one hour, it will use 0.06 KWh in one hour. If you had the light turned off for one hour, you would see an energy saving of 0.06 kWh. If you use fluorescent light bulbs, most fixtures take more than one light so you need to determine how much you will save based on two light bulbs. If the light switch controls more than one light fixture, you will need to calculate the savings for all of the fixtures on that on switch.

To find out how much money you will be saving you will need to look at your electricity bill to see what you are paying per kWh, both in general and during peak periods. Then you will need to multiply the rate per kWh by the amount of energy that you saved to get the value of the savings. For example, if you pay $1.00 per kWh and you have saved 0.06 kWh by turning off your light you would see a savings of 60 cents. The amount that you will be saving is going to increase based on different factors, such as the more you pay for electricity, and the more light bulbs that you turn off or that are controlled on one switch.