Compact AC Fluorescent Lights Jerry Fetterman ©1990 by Jerry Fetterman In our remote home, we have progressed from kerosene lights, to Aladdin lamps, to propane lights, to 12 volt DC aircraft lights, to DC fluorescent fixtures and finally to compact AC fluorescent lights. And now my wife is happy! You see, my wife, the daughter of a General Electric lighting engineer, grew up in a house where almost every other light was a three-way (100-200-300 watt) incandescent bulb, and she has always had a great aversion to fluorescent lights. So why is she happy? First of all, compact AC fluorescent lights give off that warm yellowish hue which is characteristic of incandescent lights. Second, because compact fluorescents fit in ordinary lamp fixtures, my wife can place lights all over our living and dining room area in order to eliminate those dreaded shadows. Third, since compacts have electronic ballasts they do not hum or flicker. And finally, they provide adequate light for reading without her having to snuggle up to the light with her book or magazine. After trying several of the lights in our home, I decided to do a semi-scientific study of the various models currently available on the market. In this study I wanted to measure for each model the amount of power consumed and the amount of light produced. To do this, I wired a socket to the output of a Statpower 100 watt inverter, mounted the socket on the ceiling of our mostly-white bedroom, and placed a large amorphous panel (a Sovonics L100) on the bed approximately five feet below the socket. To determine the amount of power consumed, I used a STEAMCO Solar Power Monitor to measure wattage used. To determine the amount of light produced, I used my handy Fluke portable multi-meter to measure the current generated by the panel. In addition to testing seven compact AC fluorescent lights, I decided IÕd compare my results with four types of DC lights - a 40 watt fluorescent, a quartz halogen, a PL tube and an incandescent bulb. (Low voltage DC incandescent bulbs provide more light than their 110 VAC counterparts; it would take a 90 watt 110 VAC bulb to produce as much light as the 24 VDC 50 watt bulb which I tested). The results of these tests are presented in Table 1. INSERT TABLE 1 Light Output As can be seen from Graph 1, the 40 watt fluorescent fixture gives off the most light of all the lights tested. This is not too surprising, since it is the highest-wattage fluorescent light tested. After the 40 watt fixture, the lights producing the most illumination are the 18+ watt compact fluorescents and the 50 watt incandescent bulb. On the low end of light output comes the 15 watt AC fluorescents, then the PL tube and finally the 23 watt quartz halogen bulb. INSERT GRAPH 1 Efficiency While light output is a big concern to any homeowner, efficiency is an equally important consideration, especially for alternative energy homeowners. To calculate efficiency we divide the light output by the power consumed; the resulting figures are plotted in Graph 2. As you can see from the graph, the Panasonic 18 watt fluorescent is the most efficient bulb we tested. The other eight fluorescent lights are all similar to each other in efficiency, with the Osram 20 watt bulb being the most efficient and the QÕLite being the least efficient of the group. The incandescent and quartz halogen bulbs are the least efficient, being one-third to one-half as efficient as the fluorescent bulbs. INSERT GRAPH 2 Cost Cost is often a major factor in deciding which model to purchase. With light bulbs there are two cost factors: 1) the initial cost and 2) the power and replacement cost. The initial cost for a bulb can vary from $2 for an incandescent to $58 for a 40 watt fluorescent (which includes a fixture). The power and replacement cost was calculated based on the cost of using a light for three hours a night for 10 years. Included in the calculations were initial cost, replacement cost (if lifespan was less than 10 years), photovoltaic panel cost, battery cost, and inverter cost ($20) on AC models. The results of these calculations are detailed below. INSERT BULB COST TABLE As can be seen from the above table, with regard to initial cost the incandescent bulb is the least expensive bulb tested and the 40 watt light fixture was the most expensive. But if you factor in power and replacement costs the incandescent bulb is one of the most expensive and the PL light is the least expensive. If you eliminate the cost of an inverter from the calculations on the AC bulbs, the Panasonic 15 watt ends up the least expensive bulb tested. Cost Effectiveness To determine the performance you can expect for your dollar outlay, we divided the light output by the initial, replacement and power costs. The results of these calculations are shown in Graph 3. INSERT GRAPH 3 This graph shows that the AC compact fluorescent will provide you more light output for your dollar invested (in lights, panels, batteries, and inverter) than any other type of light tested. And specifically, the Panasonic 18 watt light will provide you with more light for less money than any other light tested. An unexpected finding is that the incandescent light will provide you with more light for your dollar invested than the PL kit; this is the result of the much greater illumination produced by the incandescent bulb. Recommendations It appears to me that the new electronic ballast AC compact fluorescents are the answer to remote home lighting. Of the AC compact fluorescents tested, the Panasonic 18 watt light is the best light for efficiency and cost effectiveness. While DC lighting has its place in emergency lighting situations and locations where simplicity is desired, I feel that for most remote homes and cabins DC lighting has come obsolete. The advent of reliable, efficient inverters had made AC power available for lighting in most remote homes. In the rare event of inverter failure, for emergency purposes the homeowner could install a few DC lights or purchase a small inverter such as a Statpower or Power Star to power lights until the main inverter is fixed. Since wiring costs are considerably lower for AC lighting, inexpensive fixtures are widely available, and AC compact fluorescent lights are the most cost effective lights, I believe a homeowner would be much better off using AC rather than DC lighting. Access Jerry Fetterman and his wife, Linda Honeycutt, are owners of Yellow Jacket Solar, POB 253, Yellow Jacket, CO 81335 ¥ 303-562-4884. Yellow Jacket Solar supplies remote home PV systems and water pumping systems to their local SW Colorado neighbors and has a mail-order catalog. Jerry and Linda have lived with photovoltaic power since 1981.