Use this page to check cfl bulb power consumption for your own cfl bulb: enter your wattage, hours of use per day and electricity rate, and press Calculate. You see your daily, monthly and yearly cost plus your yearly kWh consumption. Those same results also cover cfl bulb electricity consumption.
Wondering how much your CFL bulb power consumption adds to the electricity bill? A compact fluorescent lamp is a fluorescent lighting tube folded into the shape of a classic bulb, and it draws roughly a quarter of the watts of the incandescent it replaced. This guide turns the wattage printed on a CFL light bulb into kilowatt hours and dollars, so you can see what each fixture in your home really costs to run.
Every light bulb advertises its wattage, the rate at which it pulls electric power from the socket. A bulb rated at 18 watts draws 18 joules every second while it is switched on. The utility does not bill you in watts, though. It bills you in kilowatt hours, which measure how much energy you used over time. Understanding the link between the two is the whole key to estimating the electricity cost of any lamp.
Watts describe the energy a bulb consumes, while lumens describe the brightness you get back. In the days when only incandescent bulbs were sold, shoppers judged brightness by watts alone, so a 60-watt bulb simply meant a medium-bright lamp. With energy-saving bulbs that shortcut fails, because a CFL and an incandescent can produce the same light output from very different wattages. A standard 800 lumens bulb needs about 60 watts as an incandescent, but a CFL delivering 800 lumens needs only 13 to 15 watts. Since the 2012 FTC labeling rule, packaging has to show lumens prominently, so compare the light you get in lumens with the draw in watts.
To find the energy a CFL uses, multiply its wattage by the hours it runs and divide by 1,000:
$$\text{kWh} = \frac{\text{watts} \times \text{hours used}}{1000}$$
The cost then follows from your electricity rate:
$$\text{cost} = \text{kWh} \times \text{price per kWh}$$
A 14 watts CFL left on for 5 hours uses 0.07 kWh, for instance. Check the rate on your electricity bill, because rates vary widely between utilities and regions.
A compact fluorescent light is a fluorescent lamp bent into a spiral or folded tube so it fits the same socket as an old incandescent. The design is the reason CFL light bulbs consume so little electricity, so it helps to know the four parts that matter. For comparison, see how much energy does a pressure washer use.
Inside the glass tube is a low-pressure mix of argon and a drop of mercury vapor. When current passes through, electrons knock into the mercury atoms and excite them. As the atoms settle back, they release invisible ultraviolet radiation instead of visible light, which is the first of two conversion steps in every fluorescent lamp. Making light this way with no hot filament is why a CFL draws only 13 to 15 watts for the output of a 60 watt incandescent.
The inner wall of the tube carries a phosphor coating that absorbs the ultraviolet energy and glows in visible white light. A small electronic ballast in the base supplies the high starting voltage and then limits the current. Because the phosphor light needs no hot filament, an energy-saving light of this type wastes far less as heat, and that is where the energy savings come from. Spiral CFLs became common in the 1990s, and by 2011 compact fluorescent lamps were the dominant technology for homes in China.
The reason people switched is simple arithmetic. A compact fluorescent lamp makes light by sending current through a gas-filled tube, and almost no energy is wasted as heat. An incandescent bulb heats a tungsten filament until it glows, and roughly 90% of what it draws leaves as warmth instead of light. That gap explains why a CFL needs one-fourth to one-third of the electric power for the same brightness. Next, look at playstation 4 electricity consumption.
A handy rule of thumb says a CFL is about four times more efficient than an incandescent. Take the old wattage and divide by four, and you get the CFL that matches it. A 60 watt incandescent becomes a 15 watt CFL, because 60 × 1/4 = 15. This incandescent equivalent shortcut works well for lamps from 40 up to 150 watts.
| Incandescent bulb | CFL replacement | Approximate brightness | Power saved |
|---|---|---|---|
| 40 W | 9 to 10 W | 450 lumens | about 75% |
| 60 W | 13 to 15 W | 800 lm | about 75% |
| 75 W | 18 to 20 W | 1,100 lumens | about 75% |
| 100 W | 23 to 26 W | 1,600 lumens | about 76% |
Standalone bulb ratings for compact fluorescent lamps run mostly between 7 and 26 watts, although larger commercial versions of up to 105 watts exist. Retrofit lamps for household sockets commonly draw 7 to 20 watts.
Let's put real numbers on a living-room lamp. Suppose you run an 18 watt CFL (the replacement for a 75 watt incandescent) for 3.5 hours a day, and your utility charges $0.17 per kWh.
Energy per day is 18 × 3.5 ÷ 1,000 = 0.063 kWh. Multiply by the rate and the daily cost comes to 0.063 × $0.17 = $0.0107, a little over one cent. The 75 watt incandescent in the same lamp would burn 0.2625 kWh, which costs $0.0446 a day.
Scaling the same inputs to a full year gives these results for the electricity bill:
| Bulb type | Watts | kWh per year | Annual cost | Monthly cost |
|---|---|---|---|---|
| Incandescent | 75 | 95.81 | $16.29 | $1.36 |
| Halogen | 53 | 67.71 | $11.51 | $0.96 |
| CFL | 18 | 23.00 | $3.91 | $0.33 |
| LED | 11 | 14.05 | $2.39 | $0.20 |
Swapping that one lamp from incandescent to one of the new CFL light bulbs saves 72.81 kWh, or $12.38 every year. Multiply by every fixture in the house and the energy savings add up quickly, which is why lighting can account for about 15% of a home's energy costs.
If you only need a quick answer for a specific bulb, this table assumes the same 3.5 daily hours and $0.17/kWh.
| CFL watts | kWh per month | Cost per month | Cost per year |
|---|---|---|---|
| 9 | 0.945 | $0.16 | $1.95 |
| 13 | 1.365 | $0.23 | $2.82 |
| 15 | 1.575 | $0.27 | $3.26 |
| 23 | 2.415 | $0.41 | $5.00 |
| 32 | 3.360 | $0.57 | $6.95 |
A CFL is a big step up from an incandescent, but it is no longer the efficiency leader. Comparing the three technologies side by side shows where the CFL light bulbs sit today.
An LED produces light by moving electrons through a semiconductor, so it stays cool to the touch and wastes less energy as heat. A 16.5 watt LED matches the output of a 20 watt CFL, and a 10 watt LED can replace a 14 watt CFL for the same light as a 60-watt incandescent. LEDs also outlast CFLs, with a lifespan of 25,000 hours or more, and they dim and switch without fuss. The main trade-off is a slightly higher purchase price, which has fallen steadily; a basic LED bulb cost under $5 in the United States by 2015.
Halogen lamps are an improved form of incandescent lighting. They last longer, about 2,000 hours, but they still run hot and consume far more power than a CFL for the same brightness, and they pose burn and fire hazards near fabric or shades. A CFL beats it on cost per year in nearly every lamp.
The wattage on the base is only part of the story. The lifespan of a bulb decides how many replacements you buy, and several operating quirks of fluorescent technology affect real-world consumption.
A CFL is rated for roughly 8,000 to 15,000 hours, against only 1,000 to 1,500 hours for an incandescent. At 3.5 hours daily, 8,000 hours stretches to about 6.3 years. Over that same stretch the CFL in our example consumes 144 kWh and costs $24.48 to run, while the 75 watt incandescent would cost $102.00 and you would need roughly eight incandescent bulbs in that time instead of one CFL. The catch is that frequent on-off switching of fluorescent tubes shortens life, so lamps in closets or hallways may fail earlier than rated.
Early compact fluorescents took up to three minutes to reach full output. Modern versions reach most of it within a minute, and the delay does not raise consumption: the lamp simply draws its rated watts while it brightens. Outdoor fixtures in freezing weather waste time and energy, so choose a cold-rated lamp there.
Most CFLs are not dimmable, and putting one on an ordinary dimmer causes flicker or early failure. Dimmable models exist, yet they usually cost more and do not drop in brightness as smoothly as an incandescent. Because of this, a dimmable LED is the better choice wherever you control mood lighting.
Inside the base, a small electronic ballast starts the lamp and regulates current. Cheap ballasts can have a low power factor, but household meters bill real power only, so the wattage printed on the lamp is the number to use in the kWh formula for your electricity bill.
A CFL pays back its purchase price in electricity, yet it comes with a handling requirement that incandescents never had.
Every fluorescent lamp contains a few milligrams of mercury, a neurotoxicant, sealed inside the glass tube. The amount is smaller than the tip of a ballpoint pen, and it excites the gas to emit ultraviolet light that a phosphor coating converts to visible light. Because coal-fired power plants release mercury into the air, using less electricity can actually reduce total mercury emissions even after counting the mercury in the bulb.
Many hardware stores and local collection sites accept spent bulbs, and some countries ban putting them in regular trash. Recycling recovers the glass, metal and mercury, so count it as part of the true cost of ownership next to the electricity figures above.
Lower consumption means fewer fossil fuels burned at the power plant. The U.S. Department of Energy estimates that its lighting efficiency rule will cut carbon emissions by 222 million metric tons over 30 years, and the EPA has said that if every household replaced a single incandescent with a CFL, the energy saved could light 3 million homes. Regulation has moved quickly: the European Union banned the sale of CFLs with integrated ballasts in September 2021, and major manufacturers have already shifted production to LEDs. Still, a CFL that is working keeps saving greenhouse gas emissions for as long as it lasts.
Lighting is also one of the easiest loads to measure yourself. List each lamp in a room, note its wattage and how many hours it runs, and add up the kWh. Rooms with long-running lighting, such as a kitchen or a home office, usually account for most of the total, so they are where an efficient lamp pays back first. Repeat the exercise after a swap and compare the two totals to confirm your CFL power consumption estimates match what the meter later shows.
Single-bulb figures look tiny, so it helps to see how lighting adds up across a whole house. Most homes hold between 30 and 60 sockets, and the electricity usage of every lamp together can reach 15% of the total household energy bill.
Take a house with 24 sockets. If twelve of them hold 15 watt CFLs running 3 hours a day and the other twelve hold 60 watt incandescents running the same schedule, the CFL group uses 1.62 kWh a day while the incandescent group uses 6.48 kWh. Together that is 8.10 kWh a day, or about 2,957 kWh in a year. Replace all twelve incandescents with 15 watt CFL light bulbs and the total falls to 3.24 kWh daily, which is a drop of 60% in lighting energy consumption for the whole home.
At a typical rate of 10 cents per unit, the 4.86 kWh saved each day is worth $0.486 daily, or roughly $177 a year. At the $0.17 rate used earlier, the same savings are worth about $302. Every kilowatt hour you stop using also trims your impact on the environment.
The biggest waste is a lamp left on in an empty room. A single 23 watt CFL that stays lit overnight, eight hours, uses 0.184 kWh, which is $0.03 at $0.17. That sounds minor, but over a year it reaches 67 kWh and $11.42, more than the whole annual cost of a CFL used for 3.5 hours daily. Motion sensors and timers are the cheapest way to cut that kind of energy waste.
The lighting market has changed a lot since CFLs launched in the 1980s, and shoppers now choose among many types. These are the points that decide how much money a bulb really saves you.
Look for the Energy Star mark first. Energy Star lamps are tested for lifespan, warm up speed and brightness, and an Energy Star CFL must reach 90% of its light output within a fixed time. Then compare lumens for the light you want, and finally choose the color temperature. Warm lamps near 2700 K look like old incandescent light, while cooler 4100 K to 6500 K lamps look crisp and bluish. Energy Star models also tend to carry better warranties, which protects consumers from early failures.
A CFL costs more up front than an incandescent, but the lifespan in hours more than makes up for it. Divide the cost per bulb by its rated hours and add the electricity to get the total cost of ownership. With a $2.40 CFL rated at 8,000 hours and the 18 watt lamp in our example, the bulb adds $0.30 per 1,000 hours while electricity adds $3.06, so the lamp costs $3.36 per 1,000 hours. The 75 watt incandescent, at $1.25 per bulb and 1,000 hours, costs $1.25 for the bulb plus $12.75 for electricity, which is $14.00. Efficient bulbs usually pay for themselves in the first year of regular use, and in a well-used fixture that happens in a few months.
Sales of compact fluorescent lamps peaked around 2010, then fell as LED prices dropped, and selection is shrinking. The practical decision for most consumers is to keep installed CFLs running, since they still use about a quarter of the power of an incandescent, and buy LEDs for new fixtures.
Because compact fluorescent lamps arrived with real teething problems, a few complaints have outlived the fixes. Sorting fact from folklore helps you decide whether the CFL light bulbs already in your home are worth keeping.
This was true of early models, which needed up to three minutes. Current lamps with amalgam mercury and better electronics reach most of their output in about 30 to 60 seconds. Either way the wait costs no extra energy, since the lamp draws no more than its rated watts while it brightens. A lamp slow to brighten is usually near the end of its life.
A CFL rated at 800 lumens produces the same light as a 60 watt incandescent, because lumens measure output regardless of the technology. Brightness only appears lower when buyers pick by watts and choose a 9 watt lamp where a 14 watt one was needed. Matching lumens fixes it.
Starting a fluorescent lamp does draw a short surge, but it equals only a few seconds of normal running. If you will leave a room for more than a minute or two, turning the lamp off saves energy. The real cost of frequent switching is a shorter lifespan, so keep CFLs for rooms where lamps stay lit for long stretches, such as a kitchen or study, and use LEDs in closets.
Savings depend on use. A lamp that runs 20 minutes a day costs so little to run that the cheaper bulb price, not the wattage, dominates the decision. A 15 watt CFL used 20 minutes daily consumes just 1.8 kWh a year, worth about $0.31 at $0.17, so a replacement made purely for the environment or the electricity bill barely changes either number. Prioritize rooms where CFL light bulbs run for hours.
How you install a lamp affects how much power it draws and how long it lasts. A few small habits keep every compact fluorescent lamp near its rated performance.
CFLs run best with some airflow around the base, where the electronics sit. In a sealed globe or recessed can, heat builds up, the ballast ages faster and output drops, which is why such fixtures waste about half of the energy a CFL would otherwise save: an 18 watt lamp there can deliver the useful light of roughly 9 watts. Choose lamps marked as suitable for enclosed fixtures, and for outdoor use pick a model rated for cold weather.
Only use a CFL on a dimmer when its package says dimmable, and match it to a compatible dimmer switch. Timers and motion sensors cut the hours a lamp runs, and since kWh is watts times hours, every hour removed saves 0.018 kWh on an 18 watt CFL. Very frequent cycling shortens lifespan, so a sensor that triggers dozens of times a day suits an LED better.
Check the fixture label for a maximum wattage. A socket rated for 60 watts safely holds an 18 watt CFL, because the lamp draws far less current than the rating allows.
You do not have to replace every lamp at once. These steps cut consumption in practical order: For comparison, see dishwasher power consumption.
A final habit worth building is to read the label before every purchase. The package lists lumens, watts, color temperature and rated hours, and with those four numbers you can predict the yearly running cost of any bulb before it leaves the shelf. Write the result next to the old figure from your bill, and you will quickly see which fixtures deserve an upgrade first and which can wait for the lamp to burn out.
CFL bulbs remain a low-cost way to cut lighting energy by around 75% compared with incandescent lamps, and in the example above one 18 watt lamp costs just $3.91 a year to run. LEDs now beat them on efficiency and convenience, so buy LEDs for new installs, but there is no need to throw out a working CFL. Multiply watts by hours, divide by 1,000, apply your own electricity rate, and you can price any bulb in your home in under a minute.