Electric lighting is energy intensive and expensive. So it makes a lot of sense to use electric lighting only when needed. Day-lighting may be considered a form of conservation because it reduces the need for electric lighting. Other forms of conservation are lighting controls and task lighting. These make sure that you only use lighting when and where it is needed.
Home lighting serves many purposes. Accent lighting highlights a special area or object such as a painting. Mood lighting is creates an emotional atmosphere. However, the two biggest needs for lighting are background (or area) lighting and task lighting.
Background lighting from overhead lights creates safe conditions for getting around the home, social communication and tasks which do not require much visual discrimination, e.g., cleaning floors. Task lighting illuminates a smaller area for tasks which require higher light intensity, e.g. reading, sewing and cooking. Often task lighting is shortchanged, and area lighting is assummed to be sufficient for tasks which actually require brighter light.
There are many cases where having more task lighting and less general lighting can save energy. The ideal is to maximize the efficient llumination of a small task areas, in preference to the wasteful illumination of large areas. Of course a balance is necessary, but task lighting is often overlooked to the deteriment of comfort and energy efficiency.
High windows and skylights can be effective for daytime background lighting, with additional electrcal lighting being provided for tasks. Task lighting can take the form of desk or floor lamps and lighting underneath kitchen cabinets. LED lights are especially good for this purpose and are quite energy efficient.
Our parents used to tell us: “Turn the lights off!” They knew what they were talking about: homes use 2,000 kWh for lighting, 11% of the home energy budget. Fortunately, with current lighting control technology we can obey our parental injunction and do a lot more besides.
Lighting controls can be centralized for the whole house or implemented on a room-by-room basis. The modern central systems usually have a computer or micro-processor, keypad or touchscreen, wireless switching and or dimming controls, and may include mobile phone operation. These controls remotely toggle (on-off) power to individual or groups of lights (and ceiling fans and other devices), operate dimmers, and pre-program space lighting levels (ref. Wikopedia).
Some scenarios: 1) A room occupancy detector “seeing” your motion and noises and “hearing” your footsteps switches on the lights. When you leave the room the system notices and switches off the lights. 2) An intruder is detected, all indoor and outdoor lights turn on to alert you and discourage in intruder 3) You program in special lighting themes as: day/night,” “home theatre,” “quiet time,” and “away on vacation,” and select them as needed. 4) The photocells detect bright daylight and signal the lighting controls to dim or switch off the electric lights. (This is termed “daylight harvesting.”)
A reasonable electricity savings goal for home lighting control systems is 200 to 400 kWh per year. Other benefits include longer bulb life from dimming and reduced carbon emissions at electric power plants.
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