My wife and I recently upgraded our 5th wheel trailer to a larger, more expensive RV. One of the features in the new rig is those cute little footlights to help you see the steps and so on at night when it is dark. We have three such nightlights. They are small, about two inches off the floor, and produce a little more than 20 lumens of light each. I agreed with my Wife, and we began to leave two of them on all night. I put them on my LED change-out list but did not assign them a high importance. With the new rig, Wife had a bunch of new honey-dos to keep me occupied for several weeks or longer.

A couple of days ago the nightlights reached the top of my list. After looking them over I decided a single three-LED-element chip would suffice as a good replacement. It would provide 20 lumens of light -- about the same as what I had. I removed one of the existing nightlights and took it apart. I found it to contain a bulb labeled 194, a miniature wedge (W2.1x9.5d base) rated to use 3.8 watts at 14 volts. I also noted that the wood around the casing had charred from the heat of the bulb. Maybe leaving them on all night was not such a good idea.

I did a quick calculation and determined that using 2 nightlights for 12 hours would use 38 watt-hours. For the whole year that would total 14 kilowatt-hours. Since we currently pay $0.19 per kilowatt-hour here in southern California, that could total $2.65 for the year. Chump-change! But then I checked the lifetime of the 194; it is 1,500 hours. That would mean I should expect to use 6 bulbs during the year if I left them on every night. I found them on the Internet for $7 each, but if I had to replace the entire nightlight unit, it was more like $25 each. At that rate, I would be the chump.

I compared the costs for operating with LED chip replacements. Each LED chip draws only 0.02 amps, and two chips would only use 3 watt-hours in 12 hours, or 1.1 kilowatt-hours for the entire year. Really chump change! That works out as a 1,280% difference in operating costs. And the LED is rated for a lifetime of 100,000 hours, or 22 years of service in my application. A 22 year supply of 194 bulbs would cost over $900. A couple of the LED chips cost less than $12.  Comparative costs don't really compute.

I took some time to figure out the electrical wiring in the new rig and install the new LEDs, but that was a one-time effort. Now if Wife wants to leave the nightlights on all night and day, that's fine. I figure it will only cost me another 21 cents per year. Now that is really, really chump change!

It turns out I just happened to have a single-chip LED in stock, the ZL1. You can read about the ZL1, the smallest, fully regulated 21-lumen, 12-volt zipLED lamp available today.

copyright Sam Penny, September 13, 2010