On this page, you will find out how many watts a light bulb draws.
Ahhhh the light bulb.
Is there a more famous invention? Perhaps sliced bread, but it’s tricky to slice bread without light…
We take electricity and light for granted these days, so much so that you might even forget to flick a switch and turn it off when not in use. If you’re worried about electricity usage or want to run off-grid, then it’s important to understand the power consumption of a lightbulb.
Below we will discuss and test light bulb wattage, explain how to work it out for yourself, and calculate the total electricity required.
How Many Watts is a Light Bulb?
The average incandescent light bulb uses between 30 to 60 watts. But LED light bulbs use much less at between 6 and 11 watts.
The exact number depends on the size and type of your light bulb. There are several different technologies used to make domestic light bulbs. The majority use either traditional incandescent design or increasingly popular LED equivalents.
An incandescent bulb uses a lot more power, usually between 30W and 60W. The higher the wattage the brighter the lighting. You might find a 30W bulb in a low level lamp, while a ceiling light will be brighter at 60W.
In recent years these bulbs have been in decline as they are very inefficient. This is because they use electromagnetic radiation to generate light. A by-product of this is heat and they get very hot. This is a waste of energy and leads to a quicker burnout of the filament.
LED light bulbs are becoming increasingly popular as they use nearly 80% less energy to generate the same brightness. Most domestic LED bulbs run at less than 11W. They produce little heat and last for a lot longer. When shopping for LED light bulbs you will often find the ‘equivalent’ wattage marked. For example, a 9W LED bulb is the equivalent of a 60W incandescent bulb in brightness.
How to Find Out Your Light Bulb Wattage
There’s 3 ways you can work out the wattage of a light bulb.
- Check Product Specification
The quickest way is to look at the light bulb’s specification. The watts (W) is usually written on the box or printed on the glass.
- Use a Wattmeter
A wattmeter is brilliant for getting a live wattage reading and tracking total energy usage of any appliance. You can simply plug it into your light bulb to get instant information.
I used one to test my 50W light bulb which gave a live reading of 46.1W.
I also tested an LED 50W equivalent light bulb which ran at 9.9W.
Light Bulb Wattage Examples
Let’s take a look at specific examples of how many watts a light bulb draws. Below is a collection of modern light bulbs with their listed power ratings.
| Light Bulb Make & Model | Power Rating (Watts) |
| Schiefer Lighting Candle E12 Dimmable | 25 |
| Crompton Lamps Candle B22 Dimmable | 40 |
| Westinghouse Lighting 0430300, Frosted Incandescent | 30 |
| Schiefer Lighting GLS E27 12V Dimmable | 60 |
| Sylvania GLS E27 25V Dimmable Warm | 60 |
| Orbitec 25W Tubular E14 | 25 |
| Crompton LED Squirrel Cage ST64 | 7.5 |
| Osram LED ST64 E27 Parathom Filament | 4 |
| Osram LED G95 Globe E27 Dimmable | 7.5 |
As you can see, the power ratings vary between different light bulbs. So you should take the time to check your own appliance.
How Much Electricity Does a Light Bulb Use?
You can use light bulb wattage to work out how much electricity it uses. Plus this can be useful in understanding how much it costs to run your light bulb.
A watt (W) is a measurement of power at a single point in time. A watt-hour (Wh) is the total amount of electricity used in an hour. For example, an incandescent light bulb drawing 50W would use 50Wh when running for an hour.
Happily, electricity bills are recorded in kilowatt-hours (kWh). A kilowatt is simply 1000 watts. So a 50W light bulb running for 1 hour uses 0.05kWh.
In reality, you use a light bulb for 4 hours a day. This means a 50W light bulb uses about 200Wh or 0.2kWh electricity a day. That’s 6kWh a month and 73kWh a year.
That’s an electricity cost of $0.9 a month or $10.95 a year to run a single 50W incandescent light bulb for 4 hours a day.
Compare this to an equivalent LED bulb of 5.5W, it would use 8.03kWh a year. Around $1.20 a year. You’re saving nearly 10 bucks on every light bulb in your home by switching to LED!!
Using a Light Bulb Off-Grid
If you’re planning to use your light bulb in an off-grid situation like a power outage, RV, boat, or truck the information above is important. It enables you to pick the correct power products and calculate the run time.
The first thing to do is ensure you are using LED light bulbs. This is a no-brainer if you have a limited energy supply.
You can either use a power inverter, portable power station, or generator to generate AC electricity.
To make sure everything runs smoothly you should check two things on this equipment – wattage capacity and total energy capacity.
Your power source, like an inverter, should have a wattage capacity of at least 20% more than your light bulb. This ensures it will be able to deliver enough power as they are never 100% efficient.
Secondly, you need to ensure your energy source, like a battery, has enough energy to run the light bulb for the required amount of time. As we already know, LED bulbs use upto 11Wh electricity for each hour. This is the equivalent to 0.91Ah on a 12V battery.
If you decide to use incandescent bulbs from a 12V battery it would use a whopping 6.25Ah every hour! That’s a waste of energy in my book.
How Many Watts Does a Light Bulb Use Summary
I hope you now have a clear understanding of how many watts a light bulb uses.
There are so many different options to choose from when it comes to lighting. You might not have even thought about the bulbs until they need replacing. The good news is that finding the wattage of a light bulb is easy! It is always marked on the box to help you select the right size. If you’re looking to save electricity then it is best to choose an LED bulb in the equivalent brightness you require.
