The streetlight dimmer can be used for two different purposes. The first purpose is for the reduction of power and the second purpose is for the reduction of the light emitted.  This can be marketed towards the conservation of energy and reduction of light pollution.

The first market is for the conservation of energy.  Right now the world is experiencing an energy crisis.  Energy is therefore a valuable commodity.  California has experienced blackouts because of lack of energy.  Therefore society is looking for ways to cut back on energy usage.  One method would be to reduce the power consumed by streetlights in the late night hours.  Between the hours of 1am to 6am there are very few people who required the use of streetlights and dimming the streetlights would still illuminate the streets.  By dimming 50,000 streetlights for 5 hours for 10 years using a 100W bulb you can save 3.6 million dollars or 36.4MW.

The second market is for the reduction of light pollution.  With all the streetlights it is becoming harder and harder to see the stars.  By reducing the light emitted to the streetlights during the late night hours, this will help reduce the problem but help ensure the safety of people.

Streetlights are an expanding market.  As the population grows in the urban areas more streetlights are activated.  As you can see from these two pictures of Los Angeles in 1908 and 1999 the market for streetlights has grown.

Los Angeles in 1908

Los Angeles in 1999

From the picture below, Earth at Night, you can see the amount of streetlights that are used around the world.

Earth at Night