Most daytime lighting choices are built into good house design: the inherent energy efficiency of using the sun's light (and heat) far outweigh any gains made by using low-cost bulbs or other powered options.
However, humans still need light after the sun has gone down so there are choices to be made for the proper selection and use of lighting fixtures and equipment. Studies show that about 20% of a home's electricity goes into lighting, so the savings should not be underestimated!
Lighting falls into two different categories:
- Fixtures
These are the built-in lights that are present in many modern homes. They're popular because they are inexpensive and unobtrusive, particularly subtle recessed lights. Their presence is a boon if choices are well-made for the building but there are often far more fixtures installed than are necessary, leading to blinding levels of lighting and associated energy waste (not to mention the cost).
- Lamps
These are stand-alone lights plugged in to sockets around the home. They are much more common in homes built in the post-WW2 rush and in affordable housing projects, where there are few built-in fixtures.
Both fixtures and lamps are rated by the Energy Star system, though the measurements for fixtures are arguably better because they take other performance standards into account as well as pure energy efficiency.
Lighting efficiency is measured by luminous efficacy, using lumens as units (light delivered per Watt of electricity). As you can see from the diagrams below, the traditional incandescent bulb no longer has a place in an energy-conscious home and is far outstripped in both efficacy and lifespan by the two main modern options: fluorescent and LED lights.
Outside Lighting
Some excellent options are available for outdoor lighting, thanks to the availability of solar power. Solar lights have a photovoltaic array either built in or attached (for placement in a good spot), charge during the day and use the power to illuminate after dark. This makes them a lot safer and easier to install, as they do not need any mains wiring.
Their efficiency can be further enhanced by using motion detectors instead of leaving outdoor lights on all night. If you do need to leave lights on through the night, it's worth checking not only for Energy Star labels but also certification from the International Dark-Sky Association ( www.darksky.org) who concern themselves with light pollution as well as energy efficiency.