Reviews

By Michael Forlini on Nov 25, 2008

Comments:  This is a very good comment. I am not sure if I can answer it. The energy concern is not in the amount of energy being used to the turn a light on, but rather the amount of energy required to replace the bulb.

Turning on a light switch, unlike a mechanical device (such as a car) doesn’t require an additional charge to make the bulb illuminate. As we all know, a car uses an additional charge from as battery to start an engine. A light switch requires the same amount of charge (current) to turn on a light bulb as compared to having an illuminated bulb on.

The energy issue comes in the life cycle management of a light bulb, specifically the operating life. Naturally, decreasing the operating life of just about anything requires energy. The manufacturing process requires energy for product replacement. In order to accurately address this comment, life cycle management calculations would be warranted.

When considering operating life, it is important to point out that lights have a nominal or rated operating life. This is the total number of hours that they will provide a specified level or amount of light. However, the operating life of all types of light bulbs is impacted by how many times they are turned on and off.

The more often lights are switched on and off, the lower their operating life. The exact number of hours that switching lights on and off reduces the total operating life depends on the type of light bulb and how many times it is switched on and off. To calculate the exact value of energy savings by turning a light off, you need to first determine how much energy the light(s) consume when on. Every bulb has a watt rating printed on it. For example, if the rating is 40 watts, and the bulb is on for one hour, it will consume 0.04 kWh, or if it is off for one hour, you will be saving 0.04 kWh. The energy needed to manufacture a bulb replacement will also need to be considered.

The best rule of thumb is to turn lights off when there is a lesser chance of continuous use. Turning lights off when leaving a hotel room, work or the home is a good routine to consider.

By Ellen Dubin on Nov 14, 2008

Comments:  This is such an EASY thing to do - it should be automatic for everybody. I also turn lights out in restaurant restrooms, but I sometimes wonder about this. Since these restrooms are used so frequently, does it make sense to turn the lights on and off again every few minutes, or does that actually use more energy than simply leaving them on?