The short answer is yes you can use a laptop charger with a higher wattage, however, there are some caveats. The wattage rating of a laptop charger is a maximum rating which means that the charger is capable of providing power up to the output wattage rating and or course anything in between. 

A brief explanation of Volts, Amps and Watts.

A commonly used analogy to explain the concept of Volts, Amps and Watts is to think of electricity as water flowing through a pipe. Amps is the amount of water flowing through the pipe, Voltage is the water pressure ie. the speed at which the water is pushed through the pipe and Watts is the power exerted by the water when it exists the pipe at the other end.

Amps and Watts are Related.

Watts is calculated by multiplying the Volts by the Amps. Therefore a 19V charger with an Amps rating of 3.42A would be a 65W charger 19V x 3.42A = 65W. The higher the Amps the higher the Watts, provided the Voltage remains constant.

It’s a Maximum Rating.

The Amps and Watts rating on a laptop charger is a maximum output rating. This means that the charger is capable of outputting up to the maximum Watts rating. ie it can push up to x Amps of water through the pipe at a force of up to x Watts at the pressure (Volts) provided by the charger.

I’m still confused. Can I use a laptop charger with a higher wattage?

Yes, Your laptop has been designed to draw up to a certain amount of power when running at full power. When the laptop is idle it may only draw a small amount of power from the charger but when you are rendering a 4K video for your youtube channel and charging the battery at the same time, the laptop is going to be drawing a lot more power. The manufacturer would have calculated the maximum power draw of the laptop and will have supplied a charger with a sufficient maximum rating to be able to provide this power. This means that you can quite safely use a charger with a higher wattage (or amps) rating as the laptop will only ever draw the amount of power required at the time. If your laptop was supplied with a 65W charger we know that the laptop will never draw more than 65W, so you can use a 65W, 90W,120W, 150W, 180W, 240W or higher charger. You can not use a charger with a lower wattage rating. A 30W or a 45W charger can not supply sufficient power for your laptops needs which means you could damage the laptop and/or the charger.

The Caveats.

I said in the beginning that there were a few caveats.

1. The Voltage needs to be the same or at least very close to that required by the laptop. We would generally not recommend using a charger or more or less than 1V of what is required by the laptop. HP have 18.5V, 19V and 19.5V laptops and we’ve never had a problem with supplying either of these charger for any HP laptop. Fujitsu laptops generally require 20V, but we’ve never had a problem with 19V chargers. You can not however use a 15V charger on a laptop that requires 19V or vice versa.
2. The output tip needs to match. There are many types of tips. There is the traditional barrel tip which is a simple barrel shape connector with a hole in the middle. These are measured in the form of 5.5mm x 2.5mm which us the external and internal diameter of the tip. These need to match or else the connector will not fit or will be too loose. Some chargers have a small pin in the centre and some manufacturers (HP and Dell) that have what is known as a smart tip, where there is some electronics in the tip which is used to communicate with the laptop to ensure the correct charger is connected. Whilst these tips are physically the same size, you can not use a Dell charger on a HP laptop or vice versa.
3. The Polarity must match. Barrel connectors usually have the negative on the outer sheath and the positive inside the inner hole and to be honest we have never come across a laptop charger which is different. However, to avoid any damage to your laptop it’s usually a good idea to check the polarity against that of the laptop or your original charger.

A Laptop will normally use a positive polarity. In 16 years at Asetos Computers, I’ve never seen anything different.