Tech Talk: Dyson Hot + Cool : The Best heater/fan you can find

Posted on November 30, 2012

Murray Hill Tech TalkDyson’s AM04 Hot + Cool is the latest in their line of Air Multiplier portable fans – the difference between the Hot + Cool is that it’s BOTH a fan and a heater.

As a fan, the $449.99 CAD Dyson Hot + Cool uses Dyson’s patented Air Multiplier technology to move air around a room with no buffeting that you’d expect to get from traditional, bladed fans.  The best way to explain how exactly, the Dyson Hot + Cool works is to hear all about it from Sir James Dyson himself.

According to the Dyson website, “Air is accelerated through a narrow aperture around the fan loop. This creates a jet of hot air that passes over an airfoil-shaped ramp, which channels its direction. Surrounding cool air is drawn into the airflow, amplifying it 6 times through processes known as inducement and entrainment.” This moves a much larger volume of air than a traditional fan can., and the inducement video is taken from Steve Spangler’s (free registration required but it’s well worth it) excellent video on the Bernoulli principle.

The Dyson Hot + Cool, adds to this by being a heater, with a thermostat, that although very slow, heats the room to a programmed in temperature and keeps it there. The Dyson Hot + Cool senses the temperature of the air in a room that is being drawn into the unit. If it’s below the temperature you’ve set the thermostat at, the device keeps running and blowing heated air in the room until the air coming in is at the temperature you’ve set the thermostat at. Once that temperature is reached, the unit stops and will automatically resume when the temperature drops.

Sir James Dyson shows off the Blue and Slate Dyson AM04 Hot + Cool

Photo – Dyson: Sir James Dyson shows off the Blue and Slate Dyson AM04 Hot + Cool

The Dyson Hot + Cool is perfect for a small to medium-sized room. I use my test model in the bedroom, but it could easily heat a living room sized room.

It’s quiet, as far as fans go – I think some white noise is great coming from fans – especially if it’s used in the bedroom. There’s nothing like the steady noise of a fan to help one get to sleep!

The Dyson Hot + Cool in Silver and white

Photo – Dyson: The Dyson Hot + Cool in Silver and white

The knock against this device is the thermostat. When you use it for heating, it takes about three minutes for the fan to get up to heat. I guess that’s because the fan doesn’t use heated wires to provide the heat, rather heating stones along the inside of both sides of the amplifier unit. They heat more slowly and are heated to a lower temperature (never exceeding 200˚C) so that, as Mr. Dyson has said, “it doesn’t burn dust, so you don’t get that awful burnt dust smell.” And there’s no danger if the Dyson Hot + Cool gets knocked over – the device automatically shuts itself off.

The Dyson Hot + Cool comes with a remote that lets users turn the device on and off, select the oscillation, select heating or cooling, select fan speed and set the thermostat. It’s storable on top of the aperture – there’s a magnet that keeps it in place. The Hot + Cool can be tilted either up or down, a simple pivoting on its own centre of gravity accomplished this, and it stays where you leave it.

CONS: Only comes in one size, which restricts the size of the room it’ll heat or cool; expensive; slow thermostat.PROS: Quiet operation; heats a room up quickly once it’s up to temperature; great looking; the air multiplier means no blades, so it’s safe; magnetic remote, auto shut-off if it gets knocked over and it doesn’t get hot so there’s no danger of getting burned or no burned dust smell when it’s running.

TO SUM IT UP:  Fast, efficient and quiet heat delivered where you want it in the winter and fast, non-buffeting air in the summer – the Dyson Hot + Cool is well worth the expense.

Murray Hill is lead tech writer at You can reach Murray by email at or on Twitter at @MurrayDHill

About Murray Hill

Murray Hill has been a freelance columnist appearing regularly in some of the most prominent Canadian newspapers since 1974. He began writing about technology over twenty-four years ago and he still maintains the belief that there's a gadget or gizmo for every situation and application. His fascination with technology and gadgets has endured for over fifty years, and has led to many familial discussions about the the difference between the words "need" and "want" when referring to tech. Based in Saskatoon, connect with Murray at: Author's Note: I write a column on a single product, rather than comparing products. I do this because what I write is my personal opinion on a particular product. Sometimes I get something sent to me automatically, but mostly I ask manufacturers for a particular product to review. I usually have these products for a period of a few weeks to a few months, then they are returned. I get to keep some products - usually the ones that would cost more to ship back than they are worth - and most of those items get given away. I do get an honorarium from Communicatto for writing, but get no compensation from manufacturers or the firms representing them - so nobody buys my opinion! I also try to use photos and graphics provided, mostly because I'm a terrible photographer!

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