How many watts does a light bulb use?
A typical light bulb uses 8 to 10 watts today, because most household bulbs are now LEDs that produce a standard 800 lumens of brightness on under 10 watts. That everyday brightness used to take a 60-watt incandescent, so the number people still picture for a bulb, 60 watts, is about six times the actual draw of the LED that replaced it. Small accent and candelabra bulbs run lower, around 4 to 6 watts, while bright LED floodlights and shop bulbs climb to 15 to 30 watts.
The key point is that watts measure power drawn, not light produced. A bulb's wattage only tells you how much electricity it eats; lumens tell you how bright it is. Because LEDs turn far more of their power into light and far less into heat, they hit the same lumens as an old incandescent on a fraction of the watts. That is the whole reason a 9-watt LED and a 60-watt incandescent can light a room identically. If watts versus energy is fuzzy, our explainer on kW vs kWh sorts out the difference between power and the energy your bill charges for.
How many watts does a light bulb use by type?
For the same standard brightness of about 800 lumens, the four common bulb types draw very different watts: an LED uses 8 to 10 watts, a CFL 13 to 15 watts, a halogen about 43 watts, and an old-style incandescent a full 60 watts. Same light output, and the LED does it on roughly one-seventh the power of the incandescent and about two-thirds less than the CFL.
That gap comes from efficiency, measured in lumens per watt. An incandescent manages only about 10 to 17 lumens per watt because most of its energy leaves as heat, not light. A halogen is a slightly better incandescent at around 16 to 20. A CFL reaches 50 to 70, and a modern LED delivers 75 to 100 lumens per watt or more. LEDs also last far longer, roughly 15,000 to 50,000 hours against about 1,000 for an incandescent, which is why they have taken over. For any bulb you buy, both the watts and the lumens are printed on the package, so you can check the real draw before you screw it in.
What wattage LED replaces a 60W or 100W bulb?
A 60-watt incandescent equals about a 9-watt LED, and a 100-watt incandescent equals roughly a 15-watt LED, because you match bulbs by brightness (lumens), not by watts. Use this quick guide, reading old incandescent wattage across to the LED watts that match it: 40W incandescent (450 lumens) is about a 5-watt LED, 60W (800 lumens) about 9 watts, 75W (1,100 lumens) about 11 watts, 100W (1,600 lumens) about 15 watts, and 150W (2,600 lumens) about 27 watts.
This works the other way too. A 20-watt LED is a bright bulb, putting out roughly 1,600 to 2,000 lumens, about what a 100 to 125-watt incandescent gave, which is why a 20-watt LED floodlight lights a whole garage. When you shop, ignore the "60W equivalent" marketing on the front of the box and read the lumens: that is the number that tells you how bright the bulb actually is.
How much does it cost to run a light bulb?
A single LED bulb costs almost nothing to run: a 9-watt LED left on 3 hours a day uses about 0.03 kWh, roughly $1.60 a year at the 2026 US average rate near $0.16 per kWh. The 60-watt incandescent it replaced costs about $10.50 a year on that same schedule, so each bulb you switch saves close to nine dollars a year. Run that LED nonstop for a full 24 hours and it still only uses about 0.22 kWh, around 3 to 4 cents.
Old incandescents are where cost piles up. A 100-watt incandescent burns about 0.1 kWh in a single hour, close to 1.6 cents, against a fraction of a cent for a 15-watt LED doing the same job. Across a whole house, lighting is often 10 to 15 percent of the power bill, and switching every bulb to LED can cut that lighting cost by 75 to 90 percent. Your real numbers depend on your electric rate and how long the lights stay on, so treat these as estimates; to convert any bulb's watts into the kilowatt-hours your utility bills, see watts to kWh.
How many light bulbs can a battery or solar panel run?
A lot of them, because bulbs are such small loads. A 100Ah 12-volt battery holds about 1,200 watt-hours, of which roughly 600 (lead-acid) to over 1,100 (LiFePO4) is usable, so it can run a single 9-watt LED for 65 to 125 hours, or light ten 9-watt LEDs (90 watts total) for about 7 to 12 hours. That is why lighting is the first thing people put on an off-grid or backup system; it barely touches the battery. Our breakdown of what a 100Ah battery can run shows the watt-hour math for mixing lights with other loads.
On solar, a single 100-watt panel in good sun makes about 400 to 500 watt-hours a day, enough to run several LED bulbs for hours and recharge the battery that carries them overnight. For a cabin, a shed, or a campsite, a small panel and a battery cover lighting with room to spare; solar power for a shed walks through a full small setup. Rather than guess, add your bulbs and other loads together and run the total through the solar panel calculator for your location. If you would rather skip wiring entirely, standalone outdoor solar lights charge themselves by day and light up at night.
Do light bulbs use power when off?
A plain LED or incandescent bulb uses zero power when its switch is off; with no current flowing, it draws nothing. The exception is smart bulbs, which stay connected to Wi-Fi or Bluetooth even when the light is off so they can hear the next command, and that standby costs about 0.3 to 0.5 watts each. One smart bulb idling all year is only a kilowatt-hour or two, but a dozen of them adds up to a few dollars annually.
If you run lights off a battery or solar bank, fully switch off smart bulbs and any lit wall switches you are not using, so they are not quietly draining stored charge overnight. For a grid-powered home the standby draw is minor, far smaller than the always-on pull of a TV and its gear sitting in standby.
Frequently asked questions
How many watts does a normal light bulb use?
A normal household light bulb uses about 8 to 10 watts if it is a modern LED, which is what most homes use now. That LED replaces an old 60-watt incandescent that drew about six times more power for the same 800 lumens of brightness. Smaller accent or candelabra bulbs use 4 to 6 watts, while bright LED floodlights and shop bulbs draw 15 to 30 watts.
How much electricity does a 100 watt light bulb use in an hour?
A 100-watt incandescent bulb uses 0.1 kWh of electricity in one hour (100 watts times 1 hour, divided by 1,000). At the US average rate near $0.16 per kWh, that is about 1.6 cents an hour, or roughly 5 cents over a 3-hour evening. A 15-watt LED that gives the same brightness uses about a seventh of that, well under half a cent an hour.
What is a 100-watt bulb equal to in LED?
A 100-watt incandescent bulb is equal to about a 15-watt LED, because both put out roughly 1,600 lumens of light. You match bulbs by lumens, not watts, so look for an LED labeled "100W equivalent" or rated near 1,600 lumens. The LED gives the same brightness while using about 85 percent less power and lasting far longer.
Is 200 watts a lot for a light?
For a single light, 200 watts is a lot. A 200-watt incandescent is a specialty high-output bulb that runs hot and puts out around 3,800 lumens, and many household fixtures are rated for a maximum of only 60 to 100 watts, so a bulb that large can exceed a fixture's safe limit. If you want that much brightness safely, use an LED: a 200-watt-equivalent LED delivers the same light on only about 24 to 30 actual watts and stays cool.
Is a 20 watt light bright?
It depends entirely on the bulb type. A 20-watt LED is very bright, around 1,600 to 2,000 lumens, about what a 100 to 125-watt incandescent produced, bright enough to light a garage or work area. A 20-watt incandescent, by contrast, is dim, only about 180 to 200 lumens, closer to a nightlight. Always check the lumens rating, since watts alone do not tell you how bright a bulb is.