Does Leaving The AC Fan On Waste Electricity?

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Most air conditioning systems come with the option of a ‘Fan Mode’. Depending on the situation, fan mode could help you to cut back on the high costs of using your AC, while still providing some relief from the high temperatures.

Aircon fan mode

So, is it a good idea to use fan mode? Or does leaving the AC fan on waste electricity? Let’s find out…

What is the purpose of fan mode in AC?

The purpose of fan mode on an air conditioning unit is to circulate the air without cooling it using the condenser. It uses a lot less power than using the full AC, but it is also much less effective at cooling the room when the temperature is high – it is best used at certain times.

Fan mode is not ‘better’ than having the AC mode running at any time. Air conditioning works by changing the temperature of the air to the desired temperature you want. Fan mode can’t do that – you will usually need the full cooling mode switched on.

But, fan mode might be all you need in some situations. If the room is already an acceptable temperature but you want a breeze of fresh air, it’s ideal. If that’s the case, the fan mode is the better choice because it cuts down on your electricity bills.

Does the AC fan use a lot of electricity?

An AC fan does not use a lot of electricity – typically between 20 and 50 watts. It uses less electricity than a typical ceiling fan would, although this depends on the size of the AC unit and the size of the ceiling fan. An AC fan tends to be less effective than a ceiling fan.

Understandably, when it comes to cooling a room, the more effective a solution generally equates to how much power is consumed. The best air conditioning units will use the most electricity, but in fan mode (where they aren’t too effective) they don’t use too much.

And when you compare the size of a ceiling fan with the size of a typical air conditioning unit that’s either window- or wall-mounted, it’s obvious that a ceiling fan will use more power to get it to spin – but that the ceiling fan will be more effective too.

If you have a central AC, then fan mode might use more power than a ceiling fan and it’s likely to be more effective, but that’s to cool the entire home rather than a single room.

Central AC

Does an AC fan use less electricity than AC?

An air conditioning unit in fan mode only will use a lot less electricity than when in full cool mode. While it varies for every air conditioning unit, expect fan mode to use somewhere between 3% and 10% of the watts used when the condenser is also working.

So yes, having the AC in fan mode uses only a fraction of the electricity.

Typically, an air conditioning unit will use between 500 watts and 4500 watts – it depends on the type of AC unit, and the power level. This varies by the type of air conditioner, as you can see from the table below…

AC Unit TypeLowestAverageMost
Window AC500W900W1400W
Portable AC500W2900W4100W
Central AC3000W3500W4500W

Let’s focus on the averages only. While I can’t stress enough that every air conditioning unit is different, here’s roughly how much electricity air conditioners use in fan mode:

AC Unit TypeCooling modeFan mode
Window AC900W20W
Portable AC2900W40W
Central AC3500W100W

And that has a significant impact on how much electricity you’re using too.

Let’s use a typical rate of $0.14 per kilowatt-hour. Here’s how much power is being used for 8 hours, and the cost, with a comparison between cooling mode and fan mode:

AC Unit TypeCooling mode – electricity used (8 hours)Cooling mode – cost to run (8 hours)Fan mode – electricity used (8 hours)Fan mode – cost to run (8 hours)
Window AC7.2 kWh$1.010.16 kWh$0.02
Portable AC23.2 kWh$3.250.32 kWh$0.04
Central AC28 kWh$3.920.8 kWh$0.11

You can see immediately just how different the costs are, and how much you could save by switching to fan mode.

But it’s important to remember that fan mode is nowhere near as effective at cooling a room:

  • Cooling mode extracts the air from the room, actively cools it in the condenser, and then blows it back into the room
  • Fan mode just moves the existing air around, without changing the temperature

Fan mode can help to make you feel cooler, but it isn’t effective on a hot day because all it does is move the hot air around.

It may be better to alternate between cooling mode and fan mode, instead of leaving the unit in cooling mode for the full day.

Read more: Air Conditioner Vs Fan: Electricity Usage

Man operating the aircon

Does leaving the AC fan on waste electricity?

If you leave the fan running on your AC unit when the room doesn’t need to be cooled, you are wasting electricity. Depending on the size and style of your unit, you could be wasting anywhere between $1-3 per week, depending on how long you leave the fan running.

Air conditioning units are best used to actively cool the air, but there may be times when fan mode is all you need. Still, if the room is feeling cool enough, try to avoid leaving the fan running needlessly. The cost of electricity for using fan mode may be low, but it adds up over time.

When should I use my AC fan?

You should use your AC in fan mode when the temperature and humidity are at comfortable levels, but you want a breeze to help keep the air feeling fresh. You can also use it in the early morning or late at night, or to help remove hot air from your home.

Typically you’ll mostly be using cooling mode on your AC, but here are some times when it might make more sense to use fan mode:

1. Early morning and late evening

Even if you live somewhere where summers get pretty hot, the temperature usually drops a little overnight.

So if you can, try to use the AC in fan mode in the earlier hours, before the temperature has had the chance to rise, and in the evening as it starts to lower.

If you’ve been running the AC all day, you might find that switching to fan mode for the evening is enough to keep you comfortable without spending all that extra money to actively cool the air.

And first thing in the morning, you should try to hold off on using the full power of the AC until you really need it – so start with fan mode until the temperature becomes too warm.

Girl operating the aircon

2. Summertime to lower bills

During the warmest months, it’s not uncommon for the air inside your home to become very hot and potentially hotter than outside.

It depends on how well-insulated your home is – if you’ve insulated it well, the interior will retain a lot more heat and will become warmer than the ambient temperatures outdoors.

In these situations, your AC should be running in cooling mode – but that could cost a lot of money to bring the temperature down to comfortable levels.

So instead, start by opening the doors and windows and then running the AC in fan mode only. Do this for around 30 minutes, just to give the air a chance to circulate inside your home.

This won’t cool your home completely, but it might lower the internal temperature by a couple of degrees, which in turn will mean your AC has to use less power to get the freshened air cooled to the level you want.

You’re essentially using fan mode to take a little bit of the strain, before cooling mode kicks in to finish the job.

Aircon on wall of building outdoors

3. After long periods of inactivity

If you go through long periods of not needing your AC unit, it can be a good idea to switch the fan mode on for 30 minutes or so every few weeks.

All this does is help to blow out any dust and moisture that might have settled inside the unit.

This way, you’ll keep your AC working at its best for longer and reduce the maintenance needed on it. You don’t want to get to the peak summer months and have your AC fail on you, or smell funky because mold has been allowed to grow on the inside.


Is it OK to leave the AC fan on?

It is fine to leave the AC fan on when you aren’t actively cooling your home. In fact, it can be beneficial to help keep the AC unit working at its best. But switch it off if you aren’t feeling the benefits of the breeze, otherwise, you’re wasting electricity for no reason.

The motor needed to run the AC fan is not likely to break easily, unless you have bought a cheap air conditioner that was poorly manufactured. In most cases, the first part to fail on your AC will be the condenser.

So running it in fan mode, even for prolonged periods of time, is unlikely to cause you any long-term maintenance pain. As I’ve said above, it can help to ensure no dust or moisture settles inside the unit, thereby protecting it.

But you only need to do this in short bursts, irregularly. Don’t leave it running for the sake of it.

If you are too warm, it’d be best to use the AC in cooling mode. If the temperature is relatively comfortable but a breeze would help – and you can’t open the windows (either because the outside temperature is too warm, or you’re concerned about bugs), then using fan mode is a good idea.

Leaving it running when you don’t really need it? You could be costing yourself up to $150 a year.

Living room with aircon

Should you leave the AC fan on auto or on?

You should leave your AC fan in auto mode, rather than switching it to the ‘on’ position, if you’re trying to be energy-efficient. This only switches the fan on when the AC unit is running. You can always turn it to ‘on’ when you want the fan only, but switch it back to ‘auto’ when you are finished.

It’s pretty simple – if you leave it in the ‘on’ position, the fan will run constantly. This might be what you want, if you are trying to get some cooling benefits without the cost of running the whole unit.

But leaving it in ‘auto’ means it will only switch the fan on during cooling mode, as the AC needs to when lowering the temperature of the air.

The Bottom Line

Fan mode on an AC unit is not very effective at cooling the air, so in most cases, you’ll probably want to either run the entire unit in cooling mode or just switch it off.

However, there may be some times when the temperature isn’t too bad, or you just want to make sure the AC unit is working correctly. This is when it’s worth using fan mode only because you can make a small difference to the air temperature whilst saving a lot of electricity (and therefore money).

Be proactive with your home cooling – don’t just switch everything to ‘auto’ and let the whole AC run in cooling mode when you don’t need it to. You might only switch the fan mode on occasionally, but the savings could stack up.

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