Mythconceptions

“There is no point in my switching to energy-saving lights. The
“wasted” energy they put out heats my home, so it’s not wasted.”

This myth is addressed in Chapter 11, p71.

Notes and further reading

page no.

57Street-lights use about 0.1 kWh per day per person... There’s roughly one
sodium street-light per 10 people; each light has a power of 100 W, switched
on for 10 hours per day. That’s 0.1 kWh per day per person.

... and traffic lights only 0.005 kWh/d per person. Britain has 420 000 traffic
and pedestrian signal light bulbs, consuming 100 million kWh of electricity
per year. Shared between 60 million people, 100 million kWh per year is
0.005 kWh/d per person.

There are fewer signs and illuminated bollards than street-lights.
[www.highwayelectrical.org.uk]. There are 7.7 million lighting units (street
lighting, illuminated signs and bollards) in the UK. Of these, roughly 7 million
are street-lights and 1 million are illuminated road signs. There are
210 000 traffic signals.
According to DUKES 2005, the total power for public lighting is 2095 GWh/y,
which is 0.1 kWh/d per person.

55%-efficient generator – source:
en.wikipedia.org/wiki/Alternator. Generators in power stations are much
more efficient at converting mechanical work to electricity.

Bulb type efficiency
(lumens/W)
incandescent 10
halogen 16-24
white LED 35
compact fluorescent 55
large fluorescent 94
sodium street light 150
Table 9.5. Lighting efficiencies of commercially-available bulbs. In the future, white LEDs are expected to deliver 150 lumens per watt.