Ceiling Fans: Fulfilling the Energy Efficiency Promise

A version of this article appears in the January/February 2001 issue of Home Energy Magazine.

SHARE

Click here to read more articles about HVAC

        Ceiling fans are one of the most popular and generally well regarded of all home energy efficiency features. They have a very pragmatic appeal to those who want to cut summer electric bills. At the same time, they offer a decorative alternative to typical light fixtures. So it should come as no surprise that two-thirds of American households now have ceiling fans. Home improvement centers do a brisk and growing business in sales to do-it-yourselfers, and it’s not uncommon to find ceiling fans installed by builders in nearly every bedroom and living area in many new homes.
         But recent research suggests that it may be time for the energy efficiency community to take a second look at ceiling fans (see “Ceiling Fans 101,” p. 27). The Florida Solar Energy Center identified ceiling fans as substantial energy users and investigated a number of technologies to improve energy efficiency (see “Cutting-Edge Blades Slash Fan Energy Use,” HE, July/Aug ’99, p. 7). The Natural Resources Defense Council (NRDC) and Ecos Consulting recently undertook our own EPA-funded research to determine how much energy ceiling fans use, identify energy savings opportunities, and explore various strategies to transform this market.

                Surpassing Predictions
         Our research suggests that ceiling fans are using far more energy than previous research had predicted.There are several reasons for this. Ceiling fan sales are climbing, so older studies projected lower saturation levels than we find today. Most ceiling fan research has examined motor energy use only, but we found that lighting energy use is actually greater in most regions. Finally, the part of the country with the most fans (the South) also tends to have the highest hours of usage per fan, so regional energy consumption varies dramatically from assumed national averages.
         The U.S. Department of Energy’s Residential Energy Consumption Survey (RECS) data draw a fairly accurate assessment of the ceiling fan population by geographic region. As expected, ceiling fan ownership tends to be highest in the warmest climates, and lowest in the Pacific Coast and New England regions (see Figure 1).
         Few studies have documented average hours of operation for ceiling fan motors and lighting systems by region. Use has been measured for small samples in Florida and Canada, but far more utility research is needed to determine hours of operation with precision. To obtain a better estimate of regional and national motor energy consumption, we developed a model that correlates hours of operation with the average number of cooling degree-days (CDD) in particular census regions. Our model is calibrated with the hours of use found in the Canada and Florida studies.
         We found an average of 1.5 ceiling fans per household, or 153 million fans nationwide. Average motor use is 6.2 hours per day; lighting use averages about 3.3 hours per day. Because ceiling fan lights are often the brightest, most centrally located, and most conveniently switched fixtures in the room, average lighting use may be even higher.
        This suggests that the motors of ceiling fans use about 200 kWh per householdyear. While their lights use about 320 kWh per household-year, the total—520 kWh per household-year—is greater than the annual consumption of many new energyefficient refrigerators. In some regions, household electricity use for ceiling fans is far greater (see Figure 2). On a national basis, ceiling fans may account for as much as 5% of current residential electric use.

                The Opportunity
        If used efficiently, ceiling fans offer tremendous potential for energy savings. Such savings can come from energy-efficient motors, better blade aerodynamics, energyefficient lighting, more intelligent controls, and better education of installers and purchasers. In other words, ceiling fans could provide more comfort and better light while using less energy.
        The opportunity to improve motor efficiency is enormous, given that most ceiling fan motors today waste 80%–95% of their electricity as heat. However, only some of these savings can be captured in the near term with off-the-shelf products. The greatest opportunity to improve ceiling fan motor efficiency will happen over the long term, as marketing and incentive programs drive manufacturers to specify more efficient permanent-magnet motor designs from their original equipment manufacturer (OEM) suppliers. According to industrial efficiency expert Neal Elliott of the American Council for an Energy-Efficient Economy (ACEEE), ceiling fan motor efficiencies could be doubled or tripled by increasing typical motor cost from a mere $6 to $12 per unit.
        Recent research suggests that air flow can be increased by at least 40% at a given power level (or power level reduced by 40% for a given air flow) when flat blades are replaced with curved blades similar to propellers. This design adds little cost if the blades are made of molded materials such as plastic, but costs could rise significantly if the blades are made of wood or metal. Improvements to air flow per watt can be achieved by either motor or blade improvements, and individual manufacturers are looking for the most cost-effective and appealing ways to combine the two.
        Using compact fluorescent lamps (CFLs) could make ceiling fan lighting even more energy-efficient. CFLs offer four advantages in ceiling fan applications:
• Long life reduces the hassle of changing bulbs, especially in rooms with high ceilings.
• Energy savings may be even greater than the savings from better motors and blades.
• Light output can be much higher, given the UL limit of 60 watts per socket imposed on most light kit designs to prevent overheating.
• Lower heat output improves occupant comfort in most applications.
        However, there are also challenges associated with using screw-based CFLs in existing ceiling fans. First costs are higher, of course, though annual bulb and electricity costs are significantly lower. The globe style sold in most ceiling fan lighting kits often makes it difficult or unattractive for the user to install CFLs. In addition, motor vibration may shorten the lifetime of some CFLs, though more data are needed to verify that problem.
        The use of multiple bulbs in ceiling fans compounds energy waste. Four 60W incandescent bulbs produce less light than a single 200W bulb, just as four 15W CFLs produce less light than a single 60W CFL. In addition, the small incandescent bulbs specifically marketed for ceiling fans are even less efficient than standard incandescent bulbs of the same wattage. This makes it difficult to get enough light, especially if the fan is mounted on a high ceiling.
        Using a single, high-output compact fluorescent source offers a number of intriguing advantages (see Table 1). Most importantly, it offers very high light output with maximum convenience at the lowest life cycle cost. Making it a dedicated Energy Star fixture with a hard-wired ballast ensures that the energy savings will persist. In other words, a pinbased socket prevents the consumer from inserting a screw-based incandescent bulb into the fixture. The only bulb that can fit in the socket is an energy-efficient one.
        Improvements to controls also offer substantial energy savings, by more closely matching fan operation to room conditions and occupancy. Simply placing motor speed and direction controls in a convenient location accomplishes part of this goal. Beyond that, a number of control technologies are possible. Some utilize infrared or motionsensing technology to switch off fans after people leave the room. Others employ timers. Still others match fan speed automatically to air temperature.
        Educating fan users may be even more important. There is a widespread belief that ceiling fans automatically save energy or otherwise “freshen” the air. This leads many people to switch them on at the beginning of the warm season and leave them running continuously for months (see “Getting the Most from Your Fan,” p. 28). Better consumer education about ceiling fan operation could encourage people to switch them off when they leave the room, just as they know they should do with the lights.

                What Next? Policies and Strategies
        An important transition has begun with ceiling fans. Once thought of primarily as pieces of rotating furniture whose only differences were aesthetic, ceiling fans are now beginning to be seen as air-moving and roomilluminating devices with widely differing performance characteristics. Manufacturers have always promoted the range of wood and metal finishes available on their fans, but today, issues like motor warranty, operating noise, and measured air flow are becoming increasingly important too.
       
        A focus on energy efficiency is a natural extension of this interest in performance. NRDC and Ecos Consulting are currently working with the U.S. Environmental Protection Agency and numerous manufacturers to draft an Energy Star specification for ceiling fans. This specification would define a consensus method for testing air flow and noise that would make it possible to compare the performance of different products accurately. Fans would need to move a specified CFM per watt at each of their three operating speeds, operate below a specified noise threshold, and incorporate Energy Star-compliant lighting.
        Manufacturer King of Fans will introduce improved blade design and ded icated pin-based compact flourescent lights in a Hudson Bay product avialable at Home Depot in 2001 (see photo on cover). The arrival of an Energy Star labeling program shortly thereafter should help draw attention to efficient products already on the market, while prompting other manufacturers to make needed improvements to existing products.
     
        At the same time, there remains a need for better data from utilities and manufacturers on typical hours of use for ceiling fan motors and lights. These studies will help improve estimates of likely energy savings that can be achieved from Energy Star technology, and also guide utility efforts to reduce summer peak demand. NRDC is working with utilities to encourage additional studies of this type in a variety of regions.
        The marketing infrastructure for efficient ceiling fans will also need to grow to facilitate comparisons among competing products. It may no longer be enough to hang the fans out of reach among dozens of competing models; discerning customers will want to see for themselves how one fan’s air flow, light output, and noise compare to another’s.
        As utility programs emerge to support Energy Star ceiling fans, the same kinds of brand-building efforts that have occurred with appliances, office equipment, and lighting will also come into play. Energy Star-labeled products will be more expensive than standard products, so utility programs may need to provide financial incentives, salesperson training, merchandising, point of purchase displays, and other tools that have been effective in encouraging the sale of other Energy Star products. Many of these programs may need to focus specifically on builders and contractors, recognizing that the market for ceiling fans is broader than simply homeowners and do-it-yourselfers.
        Finally, a strong emphasis should be placed on consumer education, not just in selecting a fan, but in operating it wisely. Teaching consumers how to use ceiling fans efficiently will not be an easy job. The process can begin with more consistent and clear information on the package and in the operating manual. But it will also require spreading the word to others who influence ceiling fan operation, including builders, installers, salespeople, utilities, and consumer education specialists.

Discuss this article in the HVAC group on Home Energy Pros!