Portable air conditioner vs evaporative cooler: which cools cheaper?

A portable air conditioner and an evaporative cooler both sit on the floor and blow cooler air at you, but they work in completely different ways and cost very different amounts to run. A portable air conditioner actively refrigerates the air in the room¹, and a typical 1,000 to 1,500 watt unit costs around 26p to 39p an hour to run, roughly 14 to 20 times more than a fan². An evaporative cooler, by contrast, uses significantly less electricity and no refrigerant at all³, with fans and portable evaporative coolers drawing less than 0.1 kWh, some as low as 20 watts⁴.

The trade-off is cooling power. A portable air conditioner can pull a room down to a set temperature, typically 16°C to 32°C on a 12000 BTU model⁵, while an evaporative cooler delivers air only in the region of 3 to 5 degrees below the ambient temperature of the space⁶. Neither is a route to full energy independence: both are plug-in appliances drawing grid electricity whenever they run, and the air conditioner's cooling depends on a refrigerant circuit sealed inside the unit. But both let a household cool one room on demand without installing a fixed system, which is why they are the two most common entry points into home cooling.

The short answer: which one, and why

If the question is purely cost, the evaporative cooler wins. It uses a fraction of the electricity, needs no venting hose, no refrigerant and no window kit: most domestic models are plug-and-play, requiring only water in the tank and a nearby power socket³. If the question is whether the room will actually get cool, the portable air conditioner wins. It is a genuine refrigerator: it removes warm air from the room and vents it outside via an exhaust hose while circulating cooled air indoors⁹, and some models also double as dehumidifiers¹⁰.

The honest summary is that they are not really rivals. An evaporative cooler is a dampened fan for dry, small rooms; a portable air conditioner is a temporary air conditioning system for one sealed room at a time. Independent guidance notes that portable units use 30 to 50% more electricity than fixed systems⁷, so neither is the efficient long-term answer, but each has a place in homes where a fixed split system is not possible, such as rentals⁹.

Refrigeration versus evaporation: two different machines

A portable air conditioner is a refrigerant heat pump in a box. Inside, the refrigerant enters the evaporator as a low-temperature liquid, absorbs heat from the indoor air by evaporating at low pressure, and leaves as a low-temperature vapour¹¹. That absorbed heat is then dumped outside through the exhaust hose. The unit actively cools the air in the room¹, and because the whole mechanism sits on castors, it can be wheeled from room to another, though it can only cool small spaces¹².

An evaporative cooler contains no refrigerant at all. It uses a wet pad, soaked with cold water stored in a tank, to lower the air temperature by evaporation¹³: warm room air is drawn through water-soaked pads, naturally lowering its temperature before it is released back into the room³. This is the same physics as sweating: dry air passing over water gives up heat as the water evaporates. It is why the cooler needs a fresh air supply from open doors and windows, and why it has no thermostat built in⁶.

The practical consequence of these two mechanisms runs through everything else on this page. The air conditioner works best in a completely sealed environment, with all windows and doors kept closed while it runs⁶. The evaporative cooler needs the opposite: open windows to supply dry air. The two appliances demand opposite behaviours from the room, which is why a household that tries both often finds only one of them suits the house at all.

What each type costs to run per hour

The running cost gap is large and consistent across independent and maker figures. A typical portable air conditioner of 1,000 to 1,500 W costs around 26p to 39p per hour². Uswitch's figures, based on the July 2026 Ofgem price cap of 26.11p per kWh, put a portable unit at 0.75 to 1.5 kW and £0.20 to £0.39 per hour⁴. At the cheapest fix rates and an average 9.1 hours of daily use, a 1 kW portable unit costs £13.37 a week¹⁴.

Maker figures for specific models sit inside that range. Meaco states 35p per hour for its Cirro 12000 BTU unit⁵, 40p per hour for the Cirro+ 14000 BTU¹⁵ and 46p per hour for the Cirro+ 16000 BTU¹⁶, while its 9000 BTU MeacoCool MC Series Pro is listed at 25p per hour based on 24.67p per kWh¹⁷. electriQ quotes £1.50 per day for its AirFlex 14000 BTU model based on typical daily use of 4 hours¹⁸.

Evaporative coolers sit at the other end of the scale. Fans and portable evaporative coolers use less than 0.1 kWh, and some as little as 20 W, which is 0.02 kWh⁴. Over a hot week, that difference compounds: the air conditioner's cost is measured in pounds, the cooler's in pence. The counterweight is that the air conditioner is doing a job the cooler cannot, and buying prices reflect the same split, with portable packaged air conditioners costing between £170 and £700 depending on capacity and features¹², and entry-level portable systems starting at around £250¹⁹. For a fuller breakdown, see air conditioning running costs.

How cooling capacity in BTUs relates to temperature reduction

Air conditioner cooling output is measured in BTU, short for British Thermal Unit, another way of measuring cooling output²⁰. The bigger the room, the more BTUs needed, and the higher the BTUs, the higher the power draw: portable air conditioners typically run at 900 to 2000 W²¹. Independent guidance suggests aiming for 18,000 BTUs for the best results⁴, though most domestic portables sold in the UK sit between 9000 and 16000 BTU.

An evaporative cooler has no BTU rating at all, because it does not remove heat from the room in the way a refrigerator does. Its output is a temperature drop: air a few degrees cooler than the room, typically in the region of 3 to 5 degrees below ambient⁶. For scale, one maker's portable air conditioner test showed a 6°C reduction in about eight minutes²², though that is a maker's own claim for its own product.

What this means in practice is that the two appliances answer different problems. A 12000 BTU portable unit is rated for rooms of roughly 20 to 30 square metres⁵, and one such model is listed as suitable for home, office and conservatory use²³. An evaporative cooler is best used in small rooms and when the air is dry¹³. Neither will cool a whole house: a single portable unit cannot cool multiple rooms at once¹⁰, and packaged portables generally have less cooling capacity than split systems¹². For sizing in detail, see what size air conditioner you need.

Ideal conditions for each model: dampness, airflow and space

Humidity is the deciding factor between these two appliances. Evaporative coolers are ideal for dry or moderately humid climates, and in very humid conditions their cooling performance may be reduced³, because air that is already saturated with moisture cannot absorb much more from the wet pads. UK summer weather is often humid as well as hot, which is the worst case for this technology. Air coolers do slightly cool the air, and are more effective than fans in dry conditions², but the effect is modest.

Ventilation requirements point in opposite directions. The air conditioner needs a sealed room: air conditioning works best in a completely sealed environment, so all windows and doors should be kept closed while it is running⁶. The evaporative cooler relies on a fresh air supply provided by open doors and windows⁶. A household cannot run both strategies in the same room at once.

Room size and use also matter:

• Portable air conditioners suit bedrooms, lounges, home offices and rental properties where fixed systems may not be possible⁹, and cooling and heating models are suitable for bedrooms, living rooms, home offices and commercial spaces²⁴.
• Evaporative coolers are aimed at living rooms, bedrooms, conservatories and home offices, anywhere you need cost-effective cooling³.
• Portable units still have a place for temporary set-ups or rooms under 10 m², though for longer-term use a fixed system is the better answer⁸.
• Meaco notes that its room sizes are approximate, and that ceiling height, insulation, glazing and sun exposure can affect cooling performance²⁵.

Some portable air conditioners also double as dehumidifiers, cooling the room while helping reduce humidity and tackle damp¹⁰, which in a muggy UK heatwave is arguably as valuable as the temperature drop itself. That is covered further in air conditioning, dry mode and humidity.

Sound levels, hose venting and fitting

Neither appliance is silent, but the portable air conditioner is the noisier housemate. Portable units often operate at noise levels of up to 65 dB⁸, and because the main unit sits inside the room and vents through a hose, they may not feel as quiet or efficient as a fixed system²⁰. Most portable units have a sound pressure of approximately 56 dB during operation⁶, and one 14000 BTU model is listed at 65 dB sound pressure¹⁸. Evaporative coolers are not given dB ratings in the same way, but with only a fan and a water pump they sit closer to fan noise than to compressor noise.

Venting is the air conditioner's main installation demand. All portable air conditioners must be vented out so the heat is removed from the room being cooled²³. Independent guidance is more specific still: they need to be properly vented to the outside using a special fitting for the window, and a vent just put through an open window will let heat back in⁷. Most units are plug-and-play, needing only a power supply and a way to vent hot air outdoors²⁴, and some come with a window kit for quick setup with no permanent installation¹⁰. Standard air conditioners and portable units do not require a water connection⁶.

An evaporative cooler needs none of this. It needs water in its tank and a power socket, and it needs the window open rather than sealed. Without water it will usually still operate, but only with the same effect as a standard fan⁶. Neither appliance needs professional installation: portables are a plug-and-play set up with the hose vented out of a window or door⁶. For the noise question in depth, see how noisy is air conditioning.

The Cirro 12000 BTU portable unit is available again

For households weighing a specific purchase, stock matters this year. Meaco's Cirro 12000 BTU portable air conditioner, one of the most prominent UK models, is currently sold out, with the maker stating it will be back in stock in March 2027⁵. The Cirro+ 14000 BTU and Cirro+ 16000 BTU models are also sold out, both listed as back in stock in April 2027¹⁵. A heater version of the 12000 BTU Cirro is listed as returning in October 2026²⁷.

The Cirro 12000 BTU itself is a useful reference point for what a mid-range portable offers: 12000 BTU cooling, a 20 to 30 m² room rating, 1350 watts cooling power consumption, an A energy rating, Cool, Fan, Dry and Sleep modes, 1.6 litres per hour moisture removal, and optional app and voice control through Amazon Alexa and Google Assistant⁵. It has no inverter technology and no heating capacity⁵; inverter technology is available on selected Cirro models²⁵. Alternatives remain in stock elsewhere in the market, including electriQ's 12000 BTU P12C, rated for rooms up to 30 square metres with a 3.5 kW cooling capacity and 1550 W power input²³. For the wider field, see portable air conditioners and evaporative air coolers.