We’re back to the hot weather again this weekend in the UK, which means it’s that time once again for various outlets to ‘reveal’ the true running costs of a fan, often comparing them to air conditioning. Electricity prices may still be relatively high, but fan running costs are often a misleading and irrelevant metric.
I’ve got nothing against fans, and they are often a useful tool when it gets hot, but all too often, fans are quoted as a budget option to air conditioning, and some sites even go into intricate detail on the varying running costs of different fan types.
(Welcome to Smarter Life, our new weekly column from smart home tech expert David Ludlow. Each week, we will delve into the smart home world, past and present, analysing the biggest products and how they affect our lives.)
They don’t do the same thing
My issue with comparing fans with air conditioning is that the two devices don’t do the same thing at all. AC actually lowers the ambient temperature of a room, whereas fans move air around.
True, fans are often associated with cooling, but that’s because they make you feel cooler by helping sweat evaporate, which, as previously discussed, only works when the humidity levels are low enough.
To think of it another way, look at how fans work: they have an input side (where air is drawn from) and an output side (where the air is pushed out). They help circulate air from one place to another, and that can be hot air or humid air or cold air.
Think about how fans are used in different situations. In a desktop PC, for example, the fans have an arrow showing the direction of airflow, and are typically fitted so that the ones at the front draw in cooler air from the room, and the ones at the back push out hot air from inside the case.
In a bathroom, an extractor fan is just a fan, but its job is to take humid air created by having a shower and push it outside, helping to prevent mould growth and the like.
Then, in an oven, a fan at the back isn’t there for cooling, but to circulate hot air evenly for better cooking.
Knowing this means that fans are extremely useful, but often not as direct cooling devices. Our guide on how to make a fan more efficient looks at different options for improving airflow, but all fans are limited by the ambient temperatures available.
Air conditioning, on the other hand, works by moving heat from inside your home to outside of your house, just like a fridge works by moving heat from inside to outside. By doing this, AC actually cools a room or house down, lowering the temperature. As such, fans and AC are not directly comparable.
A fan’s running cost isn’t that important
As fans just consist of a motor and blades that create the airflow, they’re relatively cheap to run. The big difference in running cost isn’t down to the fan type, but the size of the motor. So, a handheld fan uses very little power as it has small blades and a motor, but a large room circulator fan has bigger blades and a bigger motor, so uses more power.
Bigger fans move more air than smaller fans. A personal fan might help with a cooling breeze on a hot day for yourself, but it won’t work very well if you’re trying to use it to circulate air in a large room, pulling in cool night air and expelling warm internal air.
A larger fan will move more air, so it will do a better job of circulating air, or creating a breeze that can be felt by more people or from further away.
There’s another important aspect: air volume. That’s the amount of air that a fan can circulate, and is often measured as cubic feet per minute (CFM). That figure is calculated by multiplying the air velocity in feet per minute by the fan’s output area in square feet.
The higher the CFM, the more air volume a fan can circulate. From that calculation, we can see that increasing the fan speed or increasing the fan’s surface area affects CFM. In other words, a larger fan can run slower but shift as much air as a smaller fan running much faster.
Typically speaking, you need larger fans for larger spaces to get enough air flow, so there’s no point in comparing different-sized fans on running costs.
What are a fan’s running costs?
It’s normally said that a fan uses between 70W and 150W of power, although we’ve found in testing that that’s not normally the case. For example, the Princess Smart Tower Fan used 40W on maximum power, and the very powerful Vonhaus 18” Floor Fan used 99W on maximum power. Running the fans at lower speeds reduces power: the Princess fan used just 26W on its lowest setting.
Assuming the current cost per kWh of 25.73p, that’s an cost per hour of between 0.67p per hour (26W) and 2.5p per hour (100W). Even assuming that you get a fan that uses 150W of energy, that’s 3.86p to run.
Run the most expensive fan eight hours during the night on maximum power and you’re looking at a running cost of 30.88p, or just over £9 per month (assuming you used it every night). With the fans we’ve tested, running them at lower speeds than maximum, you can probably expect to pay half that on the same basis.
It’s not the cost but what they do that counts
As we covered in our guide on how to make a fan more effective, it’s often not the direct cooling breeze that helps, but using fans to better circulate air. You can do things, such as using blowing the fan over a tray of ice to get a cooler breeze (again, fans work by moving air, whether it’s hot or cold), but ultimately fans do not have any actual cooling capacity.
If you find that a fan works for you, helps circulate enough air to keep you cool, or you’re using one in a relatively low humidity environment where the airflow will give you a cooling effect, then that’s great. Just buy a fan that’s powerful and large enough for the room and situation you want (our guide to the best fans can help).
However, if you have a home or rooms that get too hot (south-facing rooms, loft conversions and so on), then air conditioning is more important, as it will lower the ambient temperature of the room by taking heat from the internal air and moving it outside.
Our guide on how portable air conditioners work explains more, and the same process applies to portable models and split, fixed-install models. Split systems are more efficient, mind, but more expensive to install.
Air conditioning costs a lot more to run than a fan, but that’s because it’s cooling the room. Running on maximum power, the De’Longhi Pinguino 100 Silent used about 640W, which is around 16p per hour. The similar MeacoCool MC Series Pro 9000 BTU Portable Air Conditioner drew around 950W of power for similar levels as the Pinguino 100 Silent and cost around 24p an hour to run.
It’s not simply a case of saying how long AC is on for, as these devices are thermostat controlled, and will shut down when a target temperature has been reached.
Again, pure running costs aren’t the most important thing. Sure, it’s useful to get an idea of how much AC will cost to run, and then using it sparingly when required to save on costs.
However, there are other more important factors to look at: efficiency and cooling capacity. First, cooling capacity is really important. For AC to work, it needs to have sufficient cooling capacity to cool the size of room you’ll put it in.
Cooling capacity for AC units is usually available in BTU and kW. BTU is typically the standard measurement used when working out the right size of AC unit to buy. You can use a calculator, such as the one at the airconcentre to estimate the size of the unit you need.
Then, there’s efficiency, which is usually quoted as the Energy Efficiency Ratio (EER). This is usually calculated by dividing the cooling capacity in BTUs by the energy input in Watts.
For example, the De’Longhi Pinguino 100 Silent has a 10,000 BTU cooling capacity and an input power of 700W, giving an EER of 14.28.
Alternatively, you can divide the cooling capacity in kW by the input in kW. The Pinguino 100 Silent has a 2.5kW cooling capacity and 0.7kW power input, which gives us a ratio of 3.571.
As long as you’re using the same input and output values when comparing AC units, you can find one that’s more efficient (higher EER), which means you get lower running costs for the level of cooling output that you require.
Variances in AC units come down to the design, the refrigeration gas used, and so on, leading to some quite significant differences between machines. Although, it has to be said that more expensive AC units tend to be cheaper to run, so it’s often a case of what you can afford.
Get the right machine for the job
Yes, AC is more expensive to run than a fan, but it’s important to focus on the fact that air conditioning actually makes a room colder; fans just push air around. In many situations, a fan will work well, either helping cool you down or circulating air to bring in cool night air. However, there are times when fans just don’t cut it and you need AC to lower a room’s temperature.
In either case, fan or AC, it’s not so much about the running cost, but in buying a device that’s big and powerful enough for the job at hand.
