How Many Watts Does a Portable AC Use (Power Explained)

Are you thinking about buying a portable air conditioner, but you’re not quite sure if it’s worth the money yet? Before you buy your portable AC unit, you probably want to know how much it’s going to cost you each month.

When you estimate potential energy costs, it’s very useful to know how many watts your particular air conditioning unit will use. This will make it much easier to manage your electricity bills effectively.

The guide below will tell you everything you need to know to make a well-informed buying decision on a new portable air conditioner.

How To Calculate The Number Of Watts Your AC Used?

Portable AC Watt Usage

Fortunately, a very simple calculation can be used to compute watt usage for your portable AC unit. We need to know the number of amperes (amps) and the number of volts for the device. The ampere, or amps, is the amount of electricity your AC unit used. The voltage measures the force or pressure of the electricity. So, watt=amp X volt. You may see this formula written as W=A X V.

Let’s take a look at this formula in action. Let’s say that the current is 3 amps, and the voltage is 100V. Just multiply 3 by 110. That equals 330W (watts). That formula would be written as P=3A X 110V = 330 W. P stands for power.

The higher the energy-efficiency EER rating, the more energy-efficient the unit is. If your unit doesn’t have enough BTUs, it will never cool your room, and the AC unit will run incessantly.

When you can lower your watts, you will improve energy efficiency and save money.

5000 BTU417-625 W
6000 BTU500 – 750 W
8000 BTU667-1000 W
10000 BTU833 – 1250 W
12000 BTU1000 – 1500 W
15000 BTU1250 – 1875 W

The table above shows that a 12,000 BTU air conditioner can use 1500W (8 EER rating) or 1000W (12 EER rating). That means having a high energy-efficiency air conditioner with a high EER rating pays off.

Calculating Running Costs Of A Portable AC By Wattage

To calculate the running cost of a portable AC by wattage, you have to convert BTUs to kilowatt-hours. With a measurement equal to one kilowatt of power consumption per hour, you will see that a 7,500-BTU PAC consumes around 2.2 kWh, a 10,000-BTU unit 2.9 kWh, and a 14,000-BTU unit around 4.1 kWh.

In 2014, the US Energy Information Administration Estimated that one kilowatt-hour of energy cost right around 16 cents in California. Using that estimate, running a small portable air conditioner for eight hours each day would cost $2.84. Running a medium portable air conditioner for eight hours would cost $3.75, and running a large portable AC unit would cost around $5.31.

Over the course of a month, these numbers would be $85.20, $112.50, and $159.30, respectively.

But BTU ratings and hours of use aren’t the only factors affecting your operating cost; your location plays an important role as well. For example, electricity costs 21.75 cents per kWh in New York, 9.78 cents in Tennessee, and 12.74 cents in DC. The national average is right around 11.88 cents.

How to Find Wattage in an AC Unit?

Check the specification sheet for Watts

You can check your specification sheet for watts. You’ll find the power, or wattage (as watts), in the same sections as the amperage (as amperes) and voltage (as volts).

Check the specification sheet for Amperes and Volts

While you are there, you can check your specification sheer for amperes and volts. That should be in the same section as the watts. The power can be calculated by simply multiplying the number of amperes by the number of volts. For example, it could be 10A X 120V = 1,200W.

Use BTU and EER rating

You can also use the BTU and EER ratings to calculate how much power your portable air conditioner uses. Simply divide the BTU by EER rating. For example, it could be 5,000 BTU / 10 EER = 500W.

When estimating how many watts of energy different air conditioners use, a good rule of thumb is to take the BTU number and divide it by 10. That’s how you can easily calculate that 5,000 BTU AC units use 500W of energy.

Small Portable AC

What Affects Your AC Energy Use Each Day?

Several things can influence the cost to operate your portable air conditioner each month. Some of these things you can control, but others are completely out of our control.

Outdoor Climate

On those sweltering summer days, it can be next to impossible to get your room to the temperature you have your portable air conditioning unit set on. Your air conditioner has to compete against the hot air coming into your home, and that’s not a fight it will always win.

When this happens, your AC will continuously run on full blast, increasing your cost to run the unit. If you live in a hot climate, be prepared to pay more to operate your portable AC.

AC Size

The size of your air conditioner will also affect how much money you spend each month. You need to have the right size air conditioner to optimize your electricity bill. Your AC unit’s size should be based on the size of the room it will cool and how many people will typically be present in the room.

If your AC is too small, it will struggle to cool the room it’s in. And if it’s too big, you’ll be spending money you don’t need to pay to power it.

Indoor Temperature

The temperature at which you set your portable AC unit will play a significant role in how much electricity your unit uses. Whenever the air conditioner kicks on to cool the room, you are using energy. When your desired temperature is reached, the cooling cycle turns off, and the fan turns on, using much less electricity.

If you keep your unit set at a low temperature, like 62 degrees Fahrenheit, it will take your unit much longer to reach your desired temperature, increasing your electricity costs.

Open Doors and Windows

If the room you have your portable AC unit has a separate open window or door leading to the rest of the house, your unit will work harder to cool the room.

The more sealed off the room is, the less your portable AC unit has to work because the air is contained. That will reduce your costs to use it.

Cooling Techniques To Save Money

Portable ACs are the only air conditioner that doesn’t require permanent installation. If you live in a small home or apartment, this is a great way to save some money. Instead of using a central AC or buying a portable unit for each room, you can move a portable AC unit when needed.

The extra venting kits are just a simple click into place, and the castors allow you to roll it around your home with ease. The only inconvenience is remembering to move it when it’s needed. We’ll explore more about this below.

Rolling Vs. Carrying

By taking advantage of a few extra accessories, you can quickly move a portable AC from one room to another. Most portable AC manufacturers include castors with their units, and they make it easy to roll around from room to room.

The Venting

The only issue of moving it from room to room is whether you need to install a window vent every time you move the unit. If you have to, you should buy additional venting kits for the rooms you frequent the most.

Alternatively, consider a ventless model like one of these ones.

Supplemental Cooling

Now you can really start saving money. Before you begin moving your unit around, think about how often each room is occupied simultaneously. This probably doesn’t happen often, so there is no use cooling rooms that aren’t being used.

Supplemental Cooling

People Also Ask (FAQ)

Are portable air conditioners expensive to run?

The amount of money it takes to run your portable AC unit depends on your unit’s size, utility provider’s rates, and a few other factors. However, a portable AC unit is almost always cheaper than central air.

What happens if you don’t drain your portable air conditioner?

If you don’t drain your portable AC, it can overflow, which can be an issue if you aren’t around when it happens. Or, even worse, it can create mold in the evaporator coils. The mold will then be present in the air in the room and get inside your unit, causing many more problems, especially for people with allergies.

Why is my portable AC filling up with water so fast?

The main reason your AC fills up with water so fast is due to the humidity in the air. Or it could be caused by a dirty filter or a clogged condensate line.

Why is my portable AC blowing water?

Three main reasons could cause your AC to blow water. You could have too much water inside your unit, you could have a clogged condensation drain line, or you may have a clogged filter.

What size generator do I need to run a portable air conditioner?

To decide what size generator you need for your portable AC unit, you need to figure out how many watts your AC unit runs on. Once you have that information, you can get a generator that delivers enough power.


Now that you’ve read this guide, you will be able to make an informed decision when you buy a large or small portable air conditioning unit. Following the articles’ advice and knowing the equations will help you manage your electricity bills and save money each month.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.