On 18/04/2011 08:30, The Medway Handyman wrote:

Using a dimmer switch on your lights at home doesn't save very much in
electricity AFAIK, e.g. dimming to half the light doesn't reduce the
power consumption by 50% - is it different on street lights?

Yes, because you're dimming a sodium discharge lamp, not a tungsten
filament. With tungsten the lumens per watt efficacy drops dramatically
when you under-run the lamp. With a discharge lamp it may still fall
off, but to a much lesser extent.

Dimming is not new. The street lights in the road where I live were
replaced a couple of years ago. After midnight they dim to 75% output,
or so the letter from the council said.

'Intelligent' street light control seems to be becoming a large
industry, e.g. http://www.e-streetlight.com/

--
Andy