Let's take a look at a typical customer utility usage, both energy and peak
demand, for a twelve month period. This will show how lighting affects a
customer's energy usage.
This graph shows total energy usage by month in kWh. We can see how energy is used in the facility. For example base loads, which include lighting, water heating, and miscellaneous equipment, are loads that operate year round every day the facility operates. On top of this usage, heating, cooling and other seasonal usage can be estimated. The lighting load can be estimated fairly accurately in most buildings by taking a count of all the lighting in the facility and the hours the lights operate.
The demand history shown in this graph breaks out in much the same way. The
base loads - lighting, water heating and miscellaneous with seasonal loads on
top. If we decrease the lighting load by installing energy efficient equipment,
then both the base energy and peak demand loads drop. You can see that
lighting efficiency improvements almost always reduce both energy and peak demand.
This is one reason why facility managers are generally interested in improving
lighting efficiency first.
