How Many Watts Does a Light Bulb Use? LED vs Incandescent, kWh and Cost

Light bulbs used to be sold by watts, so "a 60-watt bulb" meant both how bright it was and how much power it drew. That stopped being true when LEDs took over. An LED that is as bright as a 60-watt incandescent uses a fraction of the power, so the package now leads with lumens (brightness) and lists watts separately.

Lumens vs watts

Lumens measure the light a bulb gives off. Watts measure the electricity it uses. ENERGY STAR's advice is to find the lumens you need, then choose the bulb with the lowest wattage. Packages still print the old incandescent figure as a guide, with wording like "60-watt replacement" or "soft white 60."

ENERGY STAR maps the old bulbs to minimum lumens like this:

How many watts an LED actually uses

The U.S. Department of Energy's Federal Energy Management Program compared incandescent bulbs with ENERGY STAR-certified A-type LED bulbs (the standard pear shape with a medium screw base):

So the bulb in most table lamps and ceiling fixtures, the 800-lumen "60-watt" bulb, draws somewhere around 6 to 10 watts as an LED. DOE's own purchasing example for an 800-lumen bulb shows 18 watts for a less efficient model, 11 watts at the ENERGY STAR level and 5.5 watts for the best model it found.

Find the number for your bulb

Bulb packages for medium screw-base bulbs must carry the FTC's Lighting Facts label, which lists brightness in lumens, estimated yearly energy cost, life, light appearance (color temperature) and the bulb's wattage. The wattage is usually printed on the bulb's base or neck too.

kWh: watts × hours ÷ 1,000

Energy use is watts multiplied by hours on, divided by 1,000. These are worked examples, not measurements of any product:

The watts to kWh calculator runs the numbers for your own bulbs and hours.

Running cost

Multiply kWh by your electricity rate. As an illustration at 16 cents per kWh:

• One 9-watt LED, 5 hours a day: about $2.60 a year
• One 60-watt incandescent, 5 hours a day: about $17.50 a year

Your rate is on your bill. If your utility uses time-of-use pricing, evening lighting falls inside many utilities' peak windows, though at LED wattages the difference is small.

Amps and circuits

Divide watts by volts for amps. At 120 volts, a 9-watt LED is under 0.1 amp, and even twenty of them on one circuit draw about 1.5 amps. Lighting is rarely what trips a breaker in an LED house; the watts to amps calculator does the conversion if you want to check a circuit.

Fixture ratings, enclosed fixtures and dimmers

A fixture's "60 watts max" label is about heat from actual watts. A 100-watt-equivalent LED drawing about 15 watts is well under that, but DOE notes that fully enclosed fixtures trap heat that can hurt LED performance and life, so check the package says the bulb is rated for enclosed use. For dimmers, DOE says to confirm the LED is compatible with the dimming system.

Color temperature is a separate choice from wattage: around 2,700 K is the warm white most incandescent bulbs produced, while around 4,100 K looks cooler.

Lighting in a power outage

Lighting is one of the easiest loads for a home battery. Ten 9-watt LEDs on for five hours use about 0.45 kWh, a small share of a battery's stored energy. The real question is wiring: a battery only powers circuits on its critical load panel, so the lights you want in an outage, such as the kitchen, a hallway and the stairs, need to be on those circuits.

The critical load panel planner checks whether a battery can carry the circuits you choose. Refrigerators, sump pumps and internet usually come first on the home battery and backup projects Seamless Home coordinates, with a few lighting circuits added alongside. Get a free estimate to start. Coverage is confirmed per service area rather than promised as blanket availability.