I use my laptop more than any other device I own. Working remotely online means it runs for at least 6 or 7 hours every working day. From writing articles to communicating with colleagues, it’s an essential piece of kit. If you’re like me, you’re interested in power consumption. You might want to know how much electricity it uses or the requirements to recharge when in a vehicle.
Below we will discuss and test laptop wattage, explain how to work it out for yourself, and calculate the total electricity required.
How Many Watts is a Laptop?
The average laptop uses between 30 and 60 watts when charging.
The exact number depends on the size and model of your laptop, plus the charger you are using. For example, A small Chromebook might use 30W or less when charging while a 15 inch gaming laptop can draw 60W or more.
There can be a big difference in the power consumed by these devices. When running on battery power the wattage is not too important. It is when you plug in the charger that it will start using electricity from the mains or other sources. You should see a power rating listed on your charger which is the maximum wattage your laptop will use when recharging.
How to Find Out Your Laptop Wattage
There’s 3 ways you can work out the wattage of a laptop.
- Check Product Specification
The quickest way is to look at the laptop’s specification. The watts (W) is usually written on a sticker on the base of the charger. If not, you can check the user manual or the manufacturer’s website for technical details.
- 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 laptop to get instant information.
I used one to test my Surface Pro 4 laptop which gave a live reading of 27.3W while charging.
- Wattage Formula or Calculator
If you know the amperage and voltage of your laptop you can use this to find the maximum watts. Simply use the formula Amps x Volts = Watts. Or you can head over to the ‘Watt Calculator’ to work this out.
Laptop Wattage Examples
Let’s take a look at specific examples of how many watts a laptop draws. Below is a collection of modern laptops with their listed power ratings.
| Laptop Charger | Power Rating (Watts) |
| POWSEED Universal Laptop Charger | 45 |
| USB Type C 45 Chromebook Charger for HP | 45 |
| Liveimpex Universal Portable Laptop Charger | 90 |
| DONGNI Adapter for HP Pavilion | 65 |
| Dell 45W Replacement AC Adapter | 45 |
| Lenovo AC Wall Adapter | 45 |
| MacBook Air USB-C Adapter | 30 |
| Microsoft Surface Pro 1800 | 44 |
As you can see, the power ratings vary between different laptops. So you should take the time to check your own appliance.
How Much Electricity Does a Laptop Use?
You can use laptop wattage to work out how much electricity it uses. Plus this can be useful in understanding how much it costs to run your laptop.
A watt (W) is a measurement of power at a single point in time. A watt-hour is the total amount of electricity used in an hour. For example, a laptop drawing 45W would use 45Wh when charging for an hour.
Happily, electricity bills are recorded in kilowatt-hours (kWh). A kilowatt is simply 1000 watts. So a 45W laptop charger running for 1 hour uses 0.045kWh.
In reality, you charge a laptop for 1 hour a day. This means a laptop uses about 45Wh or 0.045kWh electricity a day. That’s 1.35kWh a month and 16.42kWh a year.
That’s a rough electricity cost of $0.006 a day or $2.46 a year to charge your laptop for 1 hour every day.
Using a Laptop Off-Grid
If you’re planning to use your laptop in an off-grid situation like a power outage, car, RV, boat, or semi-truck, the information above is important. You can confidently select equipment that can deliver enough power.
You can either use a power inverter, portable power station, or generator to produce AC electricity.
To make sure your laptop charges 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 laptop. This ensures it will be able to deliver enough power as they are never 100% efficient. To charge your laptop, you will need at least 75W of power capacity. This will give you enough with most laptops, plus it’s the smallest size you’ll find an inverter to use in a vehicle.
Secondly, you need to ensure your energy source, like a battery, has enough energy to charge the laptop for the required amount of time. As we already know, it will use upto about 45Wh electricity for 1 hours charging. This is the equivalent to 3.75Ah on a 12V battery. You should also be able to find the total battery capacity of your laptop in the specification. This number will tell you how many Wh it takes to fully charge the device.
How Many Watts Does a Laptop Use Summary
I hope you now have a clear understanding of how many watts a laptop uses to recharge.
Truth is: It all comes down to the size of your device and the charge you use. You should be able to check your charge for the maximum power draw. Knowing this means you can be confident in selecting something like a power inverter that can cope with your needs. If you want to know how much electricity is required to fully charge your laptop battery then check the specification for the battery size. For accurate data, attach a wattmeter when plugged in to get an exact laptop power consumption reading.
