Efficacy is the ratio of light output from a lamp to the electric power it consumes and is measured in lumens per watt (LPW).
Click the name of each type of lamp below to see its efficacy or light output.
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Efficacy of Light Bulbs
Below is a list of different types of light bulbs and the light output of each (measured in lumens per watt):
- Incandescent: 8 - 22
- Mercury: 22 - 58
- Fluorescent: 30 - 38
- Metal Halide: 74 - 132
- High Pressure Sodium: 74 - 132
- Low Pressure Sodium: 70 - 152
LED lighting - A typical signalized four-way intersection may have three lanes per approach (two through lanes and a left turn lane), plus pedestrian crossings.
Conventional incandescent lamps in a single four-way traffic light consume roughly 85 kWh of electricity per day and cost about $1,600 per year to operate. LED lights use just 10 percent of the electricity that incandescent lamps use, so the opportunity for savings is enormous.