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LIGHTS
If the power goes out for any extended period of time, emergency lighting will become very important. While LEDs are sexy they have limitations. Most people are not aware that they are not any where near as efficient as many people hawking them portray. Of the total amount of light produced per watt a DC input compact flourescent (CFL) delivers much more light and at less cost.
LEDs are great for focused light applications (flashlights and reading lights) low level illumination, red night vision lights, and for use in places where you don't want the light source failing or where it is very hard to change the bulb. CFLs are better when you need a lot of light over a broad area (e.g. typically room lighting such as the kitchen or living room). Both types should be part of your preps.
Here is some info and a few of the better links on lights, including comparative info on various LEDs and flashlights, applicable for emergency and off-grid applications that I have found:
Efficacy and efficiency
A light can waste power by emitting too much light outside of the visible spectrum. Only visible light is useful for illumination, and some wavelengths are perceived as brighter than others. Taking this into account, luminous efficacy is a ratio of the useful power emitted to the total power and is measured in lumens per watt (lm/W). The maximum efficacy possible is 683 lm/W. Luminous efficiency is luminous efficacy divided by this maximum and so is expressed as a number between 0 and 1 or as a percentage. However, the term luminous efficiency is often used for both quantities.
When choosing lights for living applications, the Color Rendetion Index (CRI) is important. This is a comparative number to natural sunlight, where CRI = 100. Anything over 80 is usually OK, over 85 is good and anything over 90 is very good. You will need a full spectrum light to get to around 95.
Another thing worth noting is that regular flourescent lights operating off the 60Hz coming out of the wall usually have a 60Hz flicker that is generally only subconsciously noted. However, it does give some people eye strain and/or headaches. The flicker may be greater when powering the light off some non-sine wave inverters. Most of the new compact flourescent lights (the ones with a regular Edison screw-in, bulb base) and ALL the 12 or 24 VDC input ones use high frequency switching and there is no flicker.
Basically if you want a flashlight you want high lumens over a narrow angle for a long throw distance (or to be bright enough to blind an intruder). Some flashlight have focusing rings on the head for adjusting the throw angle from broad to narrow. LEDs are ideal for flashlights and will make the batteries last much longer than using incandescent bulbs. In general a low cost one is not good for much than what any cheap flashlight is good for other than longer operationon the smae batteries. See the links below for some comparisions. If you are lighting a living space and want a lot of light use CFLs and get the most lumens per watt for the same wattage. A reading light/lamp is in between.
The efficiency and lumens per watt of common lighting sources are as follows:
candle 0.04% / 0.3 (Efficiency% / lumen per W)
Incandescent
40 W tungsten 1.9% / 12.6
60 W tungsten 2.1% / 14.5
100 W tungsten 2.6% / 17.5
glass halogen 2.3% / 16
quartz halogen 3.5% / 24
tungsten-halogen 2.6% - 3.6% / 18-25
high-temperature incandescent 5.14% / 35
Fluorescent
13 W twin-tube fluorescent 8.2% / 56.3
compact fluorescent 6.6%-8.8% / 45-60
Light-emitting diode
white (low power) 2.2%-6.2% / 15-42 .
white (high power) 3.8%-8.8% / 26-60
white (prototypes) 8.8%-14.7% / 60-100
Arc lamp
xenon arc lamp 4.4%-22% / 30-150
mercury-xenon arc lamp 7.3%-8% 50-55
Ideal radiators
deal black-body radiator at 4000 K 7% / 47.5
ideal black-body radiator at 7000 K 14% / 95
ideal white light source 36% / 242.5
monochromatic 556 nm source 100% / 680
While the chart makes it look like a high efficiency LED provides about as much light as a CFL you need to understand how light is measured. If a light source emits one candela of luminous intensity into a solid angle of one steradian ( http://en.wikipedia.org/wiki/Steradian) the total luminous flux emitted into that solid angle is one lumen. There are about 12.6 steradians in a sphere. If the light source emitted uniformly in all directions it thus provides 12.6 times more light than a source that illuminates over one steradian. The light from an LED is very directional only illuminating over one to a few steradians while a CFL is nearly omni-directional illuminating most.
The directional nature of LEDs is the reason why an LED replacement for many incadescent bulbs have many LEDs pointing out in all directions and why lots of LEDs pointing in the same direction (e.g. a LED traffic light) is so bright.
LIGHTING LINKS (you should find something that lights your interest)
http://candlepowerforums.com/
Don Klipstein's Lighting Info Site!
http://members.misty.com/don/index.html
http://www.otherpower.com/otherpower_lighting.html
http://www.efficientlighting.net/
NLPIP“ Lighting Research Center
http://www.lrc.rpi.edu/programs/nlpip/index.asp
National Lighting Product Information- Screwbase CFL Products
http://www.lrc.rpi.edu/programs/NLPIP/PDF/VIEW/SR_SB_CFL.pdf
Compact Fluorescent Light Bulb Investment Analysis Worksheet
http://www.homepower.com/files/kerrcflbulbs.xls
http://www.sylvania.com/LearnLighting/LightAndColor/UnderstandingLight/
Luminance Converter
http://www.onlineconversion.com/illuminance.htm
LEDs & LED Lights
http://www.enluxled.com/
http://www.lumiled.com/led-lamps.htm
http://members.misty.com/don/led.html
http://lighting.sandia.gov/Xlightingnewsarchive.htm
http://members.misty.com/don/ledx.html
http://ledmuseum.home.att.net/ (the definitive source for LED info)
12VDC Fluorescent lights and LED lights
http://www.backwoodssolar.com/Catalogpages2/lights2.htm
12VDC Fluorescent lights
http://www.thinlite.com/products.htm
12V ballasts
http://www.thesustainablevillage.com/servlet/display/products/byCat/7/29/84/
Full Spectrum Lights
http://www.lightforhealth.com/
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http://www.fullspectrumsolutions.com/ultralux_high_definition_31_ctg.htm
http://www.soluxtli.com/
http://www.aerolights.com/energysaving.asp
Dimming Fluorescent
http://www.lutron.com/ballast/whylutron.asp
http://tinyurl.com/pcuss
Flashlights
http://www.candlepowerforums.com/vb/
http://www.flashlightreviews.com/reviews_index/reviews_index_selfpower.htm
http://www.generationgear.com/products/shakelight_comparison.html
http://ledmuseum.home.att.net/ledleft.htm
http://www.elektrolumens.com/ (VERY BRIGHT flashlights!)
http://www.equippedtosurvive.com/led_lights.htm
http://www.flashlightmuseum.com/
http://www.flashlightreviews.com/index1.html
http://www.shake-flashlights.com/
Lanterns
http://www.flashlightreviews.com/reviews/riverrock_lantern.htm
Bulbs
http://freespace.virgin.net/tom.baldwin/bulbguide.html
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http://www.pti-nj.com/obb_lamps.html
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http://www.amertac.com/
Go to nitelights and specialty lights tab, then pick utility lights from side menu. Look at the 6 and 12 in fluorescents.
I've found these lights and similar one at Lowes, Home Depot, Target, and other places. GE Home products makes similar products, and there are also several imported brands. Cost should be in the $8 to $12 range for the 12inch models.
If possible get fixtures with external 12v connections as that makes hooking up large batteries easier.
Smaller 6v versions are also available and they can be hooked in series to operate from 12v batteries.
I boondock camp a lot and use this style of lighting because it gets the most light for the the least power.
You can also buy germicidal bulbs for these fixtures.
http://www.atlantalightbulbs.com/ecart/nw012104/BULBRITEFG8T5.htm