When the heat arrives, three appliances compete for your money: the fan, the evaporative cooler (or 'air cooler') and the portable air conditioner. They are not in the same league, though: one moves air, one humidifies it, the last actually cools it. This guide explains what each really does, what it costs to run and when it makes sense, so you do not pay for a device that will not solve your problem.
What each one actually does
A fan does not cool the air: it moves it. The breeze speeds up the evaporation of sweat and gives a feeling of coolness, but the room temperature does not drop a single degree. Step out of the airflow and the effect vanishes.
An evaporative cooler passes air over a wet pad: the evaporating water lowers the blown air a little, by 2-4 °C at best. A portable air conditioner genuinely extracts heat from the room and vents it outside through a hose: it is the only one of the three that brings the room temperature down.
The evaporative-cooler trap
The evaporative cooler tempts with its price (often £60-£150) and no hose. But its performance collapses exactly when you need it: the more humid the air, the less the water evaporates, so the less it cools. And it adds humidity to the room itself.
In already-damp weather or on muggy heatwave nights, it can make the air feel clammier without really lowering the temperature. It works best in dry air, a condition rarely met during a British heatwave, when the humidity is often high.
Running cost: the real contest
This is where the comparison gets nuanced. A fan uses very little, around 20-60 W. An evaporative cooler runs at about 60-200 W. A 3.5 kW portable air conditioner draws 1.0-1.3 kW of electricity, ten to twenty times more.
- Fan: ~20-60 W, a few pence a night. No temperature drop.
- Evaporative cooler: ~60-200 W. Limited drop, and only in dry air.
- Portable AC: ~1,000-1,300 W. Real temperature drop, about £25-£35 a month in normal use.
In other words, you are not paying for the same thing: the air conditioner costs more because it does a job the other two simply cannot.
Which to choose for your situation
- Mild heat, tight budget, just want a through-draught: a fan is enough.
- Dry air and occasional heat: an evaporative cooler can help, with no miracles.
- Real heatwaves, a bedroom to cool for sleep, working from home all day: only a portable AC genuinely lowers the temperature.
- The smart combo: a well-sized portable AC plus a ceiling or pedestal fan to spread the cold air and set the thermostat a degree or two higher.
If you are after a quiet split-type portable like the Midea PortaSplit and it is sold out, track its stock on /gb and set an alert rather than settling for a cooler that will not cut it.
Frequently asked questions
Does an evaporative cooler cool as well as an air conditioner?+
No, nowhere near. An evaporative cooler lowers the blown air by 2-4 °C at best, and only in dry air. A portable air conditioner genuinely extracts heat from the room and vents it outside, so it is the only one that drops the room temperature by several degrees.
Does a fan lower the room temperature?+
No. A fan moves air and speeds up the evaporation of sweat, which feels cooler, but the room temperature does not change. As soon as you leave the airflow the effect disappears, because nothing is actually removing heat from the room.
Does an evaporative cooler really use less electricity?+
Yes, far less than an air conditioner (60-200 W versus 1,000-1,300 W). But it also cools far less: you are not paying for the same service. In a humid heatwave its low running cost does not make up for how little it does.
Can I combine an air conditioner with a fan?+
Yes, it is the best strategy. A fan spreads the air conditioner's cold air around the room, which lets you set the thermostat a degree or two higher for the same comfort and cut the running cost. The two work together rather than competing.
Is an evaporative cooler any good for a bedroom?+
Rarely in the UK. Heatwave nights are often humid, which cancels out the evaporation, and the unit adds moisture to the room. To sleep reliably cool, a quiet portable air conditioner is the only option that lives up to what you expect of it.
Read also
- How to choose a portable air conditionerThe practical guide to getting the power, noise and running cost right
- Are portable air conditioners worth itWhat they truly deliver, where the bad reviews come from and when they pay off
- Portable air conditioner running costsWhat it really costs to run, and how to read the label to pay less
- Quiet portable air conditionerWhat dB(A) to look for, and why design beats any night mode
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