How Long Can AC Run Continuously: Here’s The Answer

How Long Can Ac Run Continuously: Here's The Answer

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A question we get asked here at Know the Flo is if it is ok to keep an air conditioner running continuously, or how long can you safely keep an AC running.

And considering how hot it can get in the summer, and how much of a relief a good air conditioner can bring, I totally understand. Believe me – there are days when I wouldn’t even consider turning my air con off!

Can You Run Your Air Conditioner Continuously?

The good news is, you don’t necessarily have to turn your air con off.

You can run pretty much any high quality air conditioner continuously, 24 hours a day, 7 days a week, safely and effectively and without overtaxing the unit.

Some will claim that this is true of all types of ACs – central air, split air conditioners and even smaller window mount air conditioners – though most experts do say it is best to give smaller air conditioners a rest from time to time, and would recommend that a smaller window mount air conditioner be run no more than 8-10 hours at a time, giving in a several hour break before cranking it up again.

Larger window and wall mount air conditioners can be safely run a bit more – 10-12 hours at a stretch – and generally even the most cautious authorities agree that split air conditioners and central air conditioning can be run all the time without worry.

Should You Leave Your AC Running All the Time?

Even if we assume that the air conditioner itself can handle being run for hours and hours a day, or even continuously, there are maybe a couple of considerations I should mention, things which might determine whether you really want to run your AC unit continuously.

People worry that running an air conditioner all the time, or for hours on end, might shorten the lifespan of the AC, but this is really exactly what they are designed to do, and if you have even a fairly decent quality unit this is not a real concern.

A more important question for some people is the quality of the air, and yes, running an air conditioner for hours and hours every day, or even non-stop, will definitely dry out the air in your home or office. Of course, in some places this is a good thing, but a lot of people don’t really like the effects this continuous dehumidification has on their skin, their sinuses or their health. 

But the big concern for most of us is cost – so rather than ask how many hours should an ac run per day, maybe the better question is how many hours can you afford!

How Long Can Ac Run Continuously: Here's The Answer

How Much Does It Cost to Run an AC Continuously?

There’s no question that air conditioners are expensive to run, and to run any type of air conditioner continuously can quickly become a pretty costly proposition.

While there is no easy or reliable way to say exactly how much you would spend running an air conditioner continuously – it depends on how hot the day is, the size, condition, efficiency and age of the AC itself, the size of the room, the energy costs in your area and other factors – we can make some educated estimates.

And we see that a typical new window mount air conditioner – say a 6,000 BTU unit – can cost around 2 dollars a day to run all day and night. This means 60 dollars a month for 24 hour non-stop usage.

A mini-split air conditioner – in this case a typical 24,000 BTU unit – can cost around 8 dollars a day to run continuously. This means 240 dollars a month for 24 hour non-stop usage.

A central air system – we’ll use a common 3 ton system – can cost around 15 dollars a day to run continuously. This means 450 dollars a month for 24 hour non-stop usage.

These are all approximations, based on using new, energy efficient air conditioners on hot days, and also based on average energy costs – again, these figures can change dramatically, depending on cost of electricity in your area, the age and condition of your air con, the outside temperature and a lot more – and, unfortunately, this often means the running costs will be even higher.

So, if you are wondering if it is ok to run an air con all the time, or how long you can run an air conditioner without problems, continuous running is usually not a problem for the air conditioner, but may be a bit of a problem for your wallet.

Does Temperature Matter?

People also frequently ask how long an air conditioner should run at various temperatures:

  • How Long Should an AC Run on a 100 degree day?
  • How Long Should an AC Run in 90 degree weather?

…questions like that.

And again there are too many variables to answer these questions directly, and the real answer is that you should use your air conditioner for comfort, and use it as much as you need to keep your space and yourself cool.

Now if it seems like you need to run your air conditioner too much, for too many hours a day, in order to reach the temperature you’ve set on the thermostat, it is possible that the AC unit is working too hard, which for one thing means it is probably costing you even more to run.

There are a few things you can think about and to to make your air conditioner work better, more efficiently and effectively, and be less expensive to use:

Keep Your AC Well Maintained – at the very least, keep your AC’s ducts and filter clean, and replace the filter as often as every six months for the most effective and efficient cooling. You should also consider having annual maintenance done by a licensed HVAC professional – a must for central air and very important too for splits, but also highly recommended for window and wall mount units.

Make Sure the AC is the Right Size – if you have central air this is not such a question, since the system was (hopefully, at least) selected based on the square footage of your home. With splits, window and wall mount units, though, an AC that is too small will have to work too hard and too long, will be more expensive to run than it needs to be, and will probably still not get you to the temperature you want.

In general we can say that you need about 20 BTU for 1 square foot, so for a 300 square foot room you would want a window mount or wall mount AC of about 6,000 BTU. The same formula applies for larger split air conditioners, but you should keep in mind that if there are multiple blowers – that is, if the split is cooling more than one room – you should consider the total square footage. Also, rooms with very high ceilings and open areas might require more BTU.

Keep Unused Areas Sealed Off – whatever kind of air conditioner you are using, it always helps to cool only the rooms and areas you are occupying and using. Unused rooms and spaces should be closed off, and along those lines make sure all outdoor windows are closed and sealed. It should also not go without saying that insulation is very important, and a well-sealed and well-insulated home will be more efficient and save you money all year long.

How Long Can Ac Run Continuously: Here's The Answer

Conclusion: How Long Should You Run Your Air Conditioner?

Modern air conditioners are designed for heavy-duty continuous use, and from the standpoints of safety and reliability there is no problem running an air conditioner for hours and hours at a time, and doing this on a regular basis.

Many experts would say that a central air conditioner, or even a split air conditioner, can be left on continuously, 24 hours a day and 7 days a week, but might suggest that smaller wall-mount or window-mount units be given a break occasionally – say, no more than 8-10 hours at a time, or up to 12 hour for larger models.

There are other considerations beyond safety and reliability which might make you decide whether it is a good idea to run your air conditioner for shorter stretches, and for many people an important one is the quality of the air, as AC units can have a strongly dehumidifying effect.

The most important factor for most, though, is cost, and air conditioners can be very expensive to run continuously – especially central air, but the cost of running splits and even window-mount AC units non-stop can really add up.

If you feel like your air conditioner is running too much to reach the desired temperature, it may be outsized or need maintenance, and these and other ways to cool your space more efficiently are briefly outlined just above.

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