Outdoor Portable Air Conditioner Smart Energy Use

Energy use ratings: SEER and EER

SEER (Seasonal Energy Efficiency Ratio or Rating)

SEER ratings are established by the U.S. Department of Energy to describe the energy use of portable air conditioners. A higher SEER rating means better efficiency and lower energy bills. The difference between a SEER 9 and a SEER 13, for example, can mean an energy savings of about 30%. Ratings typically range between 6 and 25.

SEER is calculated by dividing the number of BTUs by the number of watts it uses. The tests are done in a laboratory under a specific set of seasonal conditions. Since you won’t be using yours in a laboratory, your unit’s actual energy efficiency will be quite a bit different than the rating. But use the rating as a basis for comparing shopping.

EER (Energy Efficiency Ratio or Rating)

EER is similar SEER. It rates the electrical efficiency of an air conditioner, but does not take into account the seasonal factors. Since the seasonal factors of the SEER are almost impossible to duplicate outside of a laboratory, EER ratings may be much closer to the actual efficiency you can expect.

EER calculations are similar to SEER: the number of BTUs provided by an air conditioner is divided by the number of watts it uses. Period. In fact, you can even figure it out for yourself if it’s not included in the description of your portable air conditioner. Typical ratings for portable air conditioners range between 8 and 12.

Units with higher efficiency ratings may be more expensive initially, but cost savings in electricity use can offset that expense. And more efficient units typically last longer.

Operating limits

Operating limits refers to how hot, how cold, or how humid the environment is in which a portable air conditioner will be used. If it gets too cold, the motor may freeze. Not usually a problem when using an air conditioner in the summer! But high heat and humidity could be concerns. If your air conditioner will be outside in 110 / 43 degree heat, you’ll want it to be able to stand up to that heat so you won’t have to. Same with the humidity.

Check the technical specification of the portable air conditioner your are thinking about buying or renting. This will tell you the minimum and maximum temperatures within which the unit will work safely and efficiently. Many will work best in temperatures over 115°F / 45°C or under 65°F / 18°C; most will work best in a narrower range.

Also look for humidity level operating limits. Most portable air conditioners will not work properly above 60% RH (relative humidity).

Units that will work in harshest environments are called “high ambient” models. These are used in harsh desert environments and can handle temperatures up to 150°F / 65.6°C.

Electricity use

Be careful not to overload the outlet powering your unit — don’t plug other appliances into the same outlet if they’ll need a lot of power, too.

Smaller units are designed to run on typical household currents. Larger units that draw more power may need special outlets and wiring.

Keep in mind some public areas may have restrictions on electricity use which can affect your choice of outdoor cooling method. It’s a good idea to contact these places before purchasing your portable air conditioner just to be sure your unit can meet any restrictions they might have.

It’s no fun to pull out your portable air conditioner to use for the first time on a hot day, only to learn you can’t even plug it in!

Plugs and outlets

Larger, more powerful units (20,000+ BTUs) may have special plugs that aren’t compatible with certain outlets. Check the unit’s technical specifications. If your portable air conditioner will be set up long term or permanently, consider having a knowledgeable electrician rewire an outlet for you. If you will be using it in several locations it’s wise to check into what kinds of outlets are available where you will be using it. If you need more cooling than a standard outlet will supply, consider using multiple smaller units, or providing your own portable power with a generator.

All plugs on portable air conditioners have a grounding (earth) pin that helps prevent electrical shorts and fires. Newer models may have a LCDI (Leak-Current Detection and Interruption) plug. These detect any leaking current, which would happen if the cord was damaged or frayed, which could cause a fire.

For personal safety some units are fitted with a GFCI (Ground Fault Circuit Interrupter) that detects power fluctuations that might cause electrocution and shuts off the appliance immediately. Both LCDI and GFCI plugs have “Test” and “Reset” buttons that are simple to check whenever you set up your portable air conditioner.

Look for models that use the most common plug / outlet configurations for your area and are compatible with the electricity supplied to your area. Read our page on basic electricity for more information on plug types and electrical supply. Review the technical specification of the unit(s) you are considering.


The energy use of any electrical appliance is measured in watts per hour. It may withdraw large amounts of electricity (amps), and the amount of amps tells you what kind of electrical outlet the unit needs. But how those amps are used — how much is converted to watts — shows how much power the unit really has. Large units may list their electricity use by “kilowatts which is simply 1,000 watts. The number of watts used will also help you estimate operating costs.

CFM (Cubic Feet per Minute) / CMS (Cubic Meters per Second)

The amount of air a portable air conditioner can move is measured in cubic feet per minute (CFM) or cubic meters per second (CMS). These ratings for portable air conditioners serve a different purpose than they do for outdoor fans. An outdoor fan’s cooling ability is based entirely on moving air, so those numbers are high compared to an air conditioner.

A portable air conditioner’s airflow is sometimes broken down into two areas: the evaporator and the condenser. A certain amount of airflow is needed inside the unit across the evaporator and condenser coils to achieve temperature reductions. In general, look for CFM of around 400 per 12,000 BTU / ton of cooling capacity, or look for CMS of around .1888 per 12,000 BTU / ton of cooling capacity. Learn more about BTUs and choosing the right size for your portable outdoor air conditioner.

Other Outdoor Cooling Methods

If you have a more open outdoor area that needs cooling, consider outdoor fans, misting systems, or misting fans which combine misting systems and outdoor fans into a single unit.

Swamp coolers (desert coolers) use a similar technology as misting systems (evaporation cooling), but in a contained unit. They are sometimes called air conditioners, but use a different technology than true air conditioners.

Outdoor shades are a nearly universal solution that combine well with every other cooling option.

Take a look at our comparison page to learn which outdoor cooling solutions may be best for you.