Now that we have a battery and a way to charge it up, it's time to begin thinking about how we will consume the power stored in it. "Why do I need to read an article on how to make a battery dead?" you ask. Simple, it's difficult to consume battery power efficiently. In order to make the simple yet more complicated, we'll break down the various loads into categories. This issue, the subject is lighting.
Probably the most important contribution to comfort in your house truck or bus a power system can make is to replace the use of candles or lanterns. Several different types of lighting appliances are available, and you may decide to choose to use a mixture of types depending of your individual application. Briefly, here are the most commonly available types.
Incandescent: The most familiar type of light, the common light bulb. While they are inexpensive and readily available, they rate at the bottom of the efficiency chart, as only 10% of the power fed to them emerges as light, the rest is wasted as heat. Incandescent lamps can be installed in ordinary household fixtures, in which case standard line voltage lamps can be run from an inverter or shore power, or 12 volt medium-base bulbs can be used and powered directly from the batteries. Low voltage installations can also use automotive tail and marker lamps which are installed in special recreational vehicle (RV) fixtures. Incandescent lamps are a good choice for general lighting where ample power is available and efficiency is not a big factor.
Halogen: These lamps use a tungsten element immersed in halogen gas, enclosed in a quartz envelope. They are slightly more efficient than incandescent lights, and provide an intense, very white light. Nearly all halogen lamps will be of the low voltage variety, most commonly those used in track lighting. They operate at a very high temperature and require special fixtures to mount the lamp, focus the light, and endure the heat. These lights are very good for areas which require intense lighting, but beware, they tend to cast harsh shadows and would never be considered "mood lighting". Replacement lamps are fairly costly, and they do not tend to last an unusually long time.
Florescent: We're not talking here about the familiar core-coil ballasted, long tube florescent lights you see on the ceiling of the super market. Florescent lighting has come a long way from the blue-green nightmares that made food turn a disgusting color right before your eyes. Modern fluorescents are now electronically ballasted and are color corrected to resemble sunlight in a most pleasing manner. These lamps put out four times more light per watt consumed than incandescents and operate cooler as well. The popularity of compact florescent lights grows daily. These lamps can be installed in standard medium-base fixtures and come in a variety of wattages (remember, a 25 watt CF will put out the light of a 100 watt incandescent). They are also available in low voltage electronically ballasted models as well. Use florescent lighting anywhere that a good quantity of light is needed for a prolonged period (their life is shortened by turning on-and-off frequently). These lamps are somewhat expensive, but will last ten times longer than standard bulbs, and are very well suited for use on a battery powered-system.
LEDs: Light Emitting Diode lighting for general illumination is still in it's infancy, but these solid-state devices promise to revolutionize that way we light our homes. Virtually 100% efficient, this technology will become more prevalent as the cost of white LED's drops and newer designs become available (remember, you read it here first). At this point, if you want to experiment with LED lighting, you can buy an LED flashlight, or small lamps which will install in a low voltage fixture and illuminate a small area.
As you can see, many options present themselves when choosing lighting for your home. You might decide to put a compact florescent light in your kitchen and living room fixtures, a halogen bulb for your reading lamp and an incandescent in a closet where it will be used infrequently and only for a few minutes at a time. If you are on the road a lot and your engine keeps the batteries full a good bit, why bother with efficiency? If you find yourself with barely enough power to keep the light above your desk running in the middle of winter, you'll want to investigate the most efficient lighting available. Most of us fall somewhere in between, and with careful consideration, there will be power enough for all.