How to save electricity on lighting Lighting is nearly tied for second place among the biggest energy users in your home . Fortunately, it's one of the easiest areas where you can save. You can start saving a whopping 70% right away simply by screwing in new CFL lights. And if you're concerned about mercury if the bulb breaks, you can either use a CFL that has a plastic cover, or use an LED lightbulb instead. Below are several strategies for saving money on lighting.   Use compact fluorescent light bulbs (CFL's). If you know only a little about CFL's, you've probably heard that they save a little energy but they contain a lot of toxic mercury. But the truth is, they save a whopping amount of energy, and the mercury scare is way overblown. (The median exposure for a broken CFL is 0.07 mcg, while six ounces of Albacore tuna has 48 mcg -- 700 times as much. See IES.org for more.) Let's start out by looking at the savings you get with CFL's. Right off the bat, you save 70% on energy as soon as you screw them in. Here's a calculator to demonstrate: Number of bulbs 1 2 3 4 5 10 15 20 Wattage (original) 60 75 100 Hours on per day 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Cost of electricity* April 2008 data, avg.! ---------------------- 23¢ (HI) 19¢ (CT) 18¢ (NY) 17¢ (AK) 16¢ (MA,ME) 15¢ (NH,RI,VT) 14¢ (DE,NJ) 13¢ (CA,MD,NV) 12¢ (U.S. avg.) 12¢ (TX) 11¢ (DC,FL,IL,PA,WI) 10¢ (AL,AR,AZ,CO,IA, 10¢ LA,MI,MS,NC,OH,SC) 9¢ (GA,IN,KS,MN,MT, 9¢NM,OK,OR,TN,VA) 8¢ (KY,MO,SD,UT,WY) 7¢ (ID,ND,NE,WA,WV) * *Rates are averages for an area. Yours may differ. Check your bill. Monthly Yearly 10 years Cost with old bulbs: $ $ $ Cost with CFL's: $ $ $ Savings: $ $ $ But there are still more savings to be had. Brand-new CFL's last 10 times longer than old-style bulbs, and they generate a lot less heat -- which means lower cooling bills. I have a separate page which covers CFL's in detail, including pro's, cons, how to shop for them, and the real story behind the mercury warnings.   Install a skylight. Using natural lighting saves a bunch of energy and produces a much nicer environment besides. Modern skylights are available which let in only the light and not the heat.   Use a motion sensor for outside lighting Exterior security lights automatically shut off after 1-15 minutes, so you're not paying to run them all night. Fixtures start at $25 at home improvement stores like Home Depot. Do not that you can't use CFL's in security lights though, because the fixtures cycle a very small amount of voltage through the lights constantly which makes the CFL's die a lot faster. Exercise: You buy a security light for $20. The light used to be on all night, for 12 hours each night. Now it's on for about an hour a night. You're using two 75-watt bulbs in the fixture. How long does it take for the security light to pay for itself? (assume electricity costs 11¢/kWh) (see answer) Old way: 2 bulbs x 75W x 12 hrs/day x 30.5 days/mo. ÷ 1000 w/kW x $0.11/kWh = $6.04/mo. New way: 2 bulbs x 75W x 1 hr/day x 30.5 days/mo. ÷ 1000 w/kWh x $0.11/kWh = $0.50/mo. Savings per month: $6.04 - $0.50 = $5.54 Payback time: $20 / $5.54 = 3.6 months   Use a motion sensor for interior lighting. If you can't remember (or can't be bothered) to turn off the lights throughout your house, a motion-sensor switch will shut them off for you automatically. You can buy motion-sensing wall switches for as little as $10 at a home improvement store.   Use the lowest-wattage bulbs for lights that are always on (e.g., stairways). Replacing 75-watt bulbs with 15-watt bulbs reduces energy usage by 80%. Replacing them with CFL's or LED lights saves even more. Exercise: How much do you save in a year by replacing a 75-watt bulb with a 5-watt bulb, for a light that's on 24/7? Use 11¢/kWh for the cost. (see answer) Old way: 75W x 24 hrs/day x 30.5 days/mo. ÷ 1000 w/kW x $0.11/kWh = $6.04/mo. New way: 5W x 24 hrs/day x 30.5 days/mo. ÷ 1000 w/kWh x $0.11/kWh = $0.40/mo. Savings per month: $6.04 - $0.40 = $5.64   (93%!)   Put nightlights on photosensors. You can get a simple screw-in photosensor for $4.50 ($8.50 for the outdoor version) which will automatically turn your light on at night and off during the day. You just screw the special socket into the existing light socket, then screw the light bulb into the special socket. Exercise #8: How long does it take for one of these $4.50 devices (indoor version) to pay for itself, assuming you were using a 60-watt bulb, paying 11¢/kWh for electricity, and saving 12 hours per day of light use? (see answer) Old way: 60W x 24 hrs/day x 30.5 days/mo. ÷ 1000 w/kW x $0.11/kWh = $4.83/mo. New way: 60W x 12 hrs/day x 30.5 days/mo. ÷ 1000 w/kWh x $0.11/kWh = $2.42/mo. Monthly savings: $4.83 - 2.42 = $2.41/mo. Payback time: $4.50 / 2.41 = 1.9 months You can also make lamps or other devices go off during the day and turn on at night by using a plug-in light sensor ($6). You plug the appliance into the sensor, and then plug the sensor into the wall. If you're handy with electrical wiring, you can mount a light sensor to a wall (like you'd mount a light switch or electrical outlet). Wire-in sensors are around $10.   Turn off lights when you're not using them, even for just a few minutes. The idea that lights use extra electricity to start up is a myth. You'll save electricity every time you turn the lights off, no matter how short the off duration, and whether they're regular lights or fluorescents. You might have heard that you wear out your lights quicker by cycling them off and on, but that effect is so small it's not worth worrying about, and you can safely turn your lights off every time you leave the room, no matter how short the duration. If you feel you need to obsess over this (as evidenced from all the email I get about the subject) then see my answer below about fluorescent cycling costs.   Replace fluorescent magnetic ballasts with electronic ones. For long-tube fluorescent lighting (as opposed to screw-in compact fluorescents), an old-style magnetic ballast might use 100W to power two 40W tubes, while an electronic ballast might use only 60W. Also, the electronic ballast eliminates flicker and usually eliminates hum. They also generate less heat, which saves additional money on cooling.   Use LED holiday lights. LED Christmas lights use 80-90% less electricity than standard holiday lights (which use 25 watts in a typical 50-bulb strand). LED lights also generate much less heat, so they're less likely to catch your Christmas tree on fire. Also, you can put a few strands of white lights on the ceiling and use it as mood lighting. LED holiday lights aren't quite as bright as standard bulbs, and the light they produce is brilliant white instead of normal yellowish light, but that's fine with us to get the 90% electricity savings. (And blue, yellow, and red are also available.) Another advantage is that the LED's are virtually indestructible -- they don't burn out like normal bulbs (not for about ten years, anyway), and they're not fragile like normal holiday lights. I actually unsuccessfully tried to crush one by standing on it on a concrete surface. I broke the decorative casing but was unable to break the LED bulb itself -- it still shone when I plugged it back in. Inirgee sells a nice variety of LED lights in a variety of colors: 120V holiday light strings, and 12V holiday light strings to be powered from a battery. Notably, most of the products carry a lifetime warranty. We have a separate page about rewiring Christmas lights to run off batteries.   LED lights: Not quite ready for primary lighting...yet LED's are great for holiday lights, accent lighting, mood lighting, and landscape lighting.  And I believe they're the wave of the future for indoor lighting too -- but they're not ready for primetime just yet, not for most people anyway. That's because: They're crazy expensive. We're talking $50+ per bulb. They send light in only one direction, so bathing a room in light is impossible (unless you use lots of bulbs). Most models put out a cold, bluish light, rather than the warm, yellowish light of a regular bulb. Most models don't put out nearly enough light. On point #3, many (most?) manufacturers don't even bother to tell you the color temperature, because if they gave you any clue as to how cold and harsh the light is you probably wouldn't buy it.  If you're shopping for lighting and you want warm light, look for a color temperature of 2700-3000K (not the 3600-5500K of cold light). What's nice about LED's is that they use even less energy than CFL's, and they don't have any mercury.  As soon as the cost comes down, the quality improves, and the light output increases,  we'll be ready to roll.  As I write this in 2010 I predict that LED's will be competitive with CFL's in terms of cost and quality by 2012 at the earliest. (Readers can feel free to write me in 2012 to remind me to update this page by then if I forget.)  In the meantime, you can use LED's if you don't mind paying more, and/or you don't need that much light for a fixture. Here's how the various lighting technologies stack up: Incandescent CFL LED Watts 100 25 13 Toxic mercury ✓ Price $0.50 $2.50 $50.00 Most online stores don't even bother to tell you how bright their LED bulbs are, in either lumens or incandescent watt equivalents, because they probably figured that if you knew how dim these bulbs were there's no way you'd buy them. One exception is the EvoLux which is the first 100-watt equivalent LED light. Unfortunately the quality is just not there yet. The $85 bulb I purchased pointed the light straight down, rather than bathing the room in light like my CFL. Another rare company to list their LED bulb output is C. Crane. Unfortunately, the biggest bulb in their catalog is only 520 lumens, compared to the 850 lumens you'd get from a standard 60-watt bulb (or a 15-watt CFL). Plus, the bulb costs a whopping $70, and it's a harsh cool white, not warm white.  They do sell a warm white bulb for $45, but it puts out half as much light as their already anemic 520-lumen bulb. LED's are great for non-primary lighting applications.  I use LED Christmas lights as mood lighting when I don't need a whole lot of light. I hung a couple of strands from hooks aroundthe perimeter of my ceiling. Yeah, the note that came with the lights said "This seasonal use product is not intended for permanent installation or use," but I guess I live on the wild side. Commercial users might like LED bulbs because they last nearly forever -- 50,000 hours of use. In an installation with lots of bulbs and where they're hard to reach and the labor cost of replacing them is high, the labor savings and energy savings together might outweigh the higher purchase costs. Commercial users will also want to check out the products at Residential Landscape Lighting. The Simple Dollar has a great review of LED light bulbs. Related pages: Questions I've received and answered about how saving electricity on lighting Compact fluorescents -- pro's, cons, and the real story behind the mercury warnings Saving Electricity 101: Start Here How much it costs / how they charge What's a Watt / Kilowatt? How much energy stuff uses How to measure electrical use Mr. Electricity is your guide to saving energy in your home. General Electricity Myths Using elec. when off? Why is my bill so high? 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