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Is it safe to leave the air conditioner on all day?

Anyone who lives in a climate where they need air conditioners will know how awful it is to come home to a house that feels like an oven.

Air conditioners are great at keeping our homes at a comfortable temperature, and it is wonderful to return to a house that feels cool while outside is boiling.

But should we leave the air conditioner on all day?

The question that often goes side-by-side with this one is whether leaving the air conditioner on all day is better than tuning it off and how much energy do we save with each option.

It has been shown that wasting energy not only costs us more money, it also contributes to global change because it burns more fossil fuels.

While it may seem like you are wasting energy by turning the air conditioner off and on, doing this does in fact save you money. Additionally, it helps your unit to work more efficiently.

Manufacturers will tell you that while the unit may have to work hard at first to get the temperatures down from 80 to 75 degrees, the systems are designed to run most efficiently at full power. It is better for them to do this than to work at shorter periods at less powerful speeds.

For the air conditioner to be able to efficiently dehumidify your home it needs to work at full speed.  

What’s the best temperature to leave it at?

If you want to stop your home feeling like an oven when you return, then you may opt for leaving it on while you are out. 

For central air conditioning or a window unit you should leave the temperature at 78 degrees or higher while the house is empty. 

Your air conditioner will use 3-5% less energy with every degree that you raise the thermostat. The best energy savings will be in the 78 degree and over position. While this will not be comfortable while you are in the house, it is the best level for the air conditioner to be at while you are out.

Leaving the air conditioner on

If you choose to leave the air conditioner on all day, you must make sure that you check the filters regularly. If they become clogged the unit will cease to work efficiently or may not work at all.

Make sure you have the correct size unit for your home. Too large a unit will mean that it continues to turn itself on and off through the day. This means an inefficient use of energy and you may end up with higher bills.

Having a unit which is too small for your home will mean that it must work far harder to maintain a constant temperature. Not only will your bills be higher, but the air conditioner will wear itself out quicker and you may end up replacing it sooner.

If the air conditioner is in the wrong place in the house, you will come home to find that the house is still at an uncomfortable level and the unit needs to work harder to cool the other areas.

If your unit is portable or placed in a window you must make sure that there is no foliage near it to stop it working efficiently.

Leaving the air conditioner off

If your house is empty for most of the day, there is no reason to keep it at the temperature you enjoy at night. This wastes money and makes the unit work harder. Turning it off then on when you get home means that it has time to rest and will make it last longer.

While it is a good idea to turn the unit off, leaving it off for extended periods are also not a good idea. Mold can start to grow in the unit and this will be detrimental to health when you turn it on again. 

On your return make sure that you lower the temperatures gradually and not all at once. This will simply overwork the system.

Other ways to cool your home

Install a programmable thermostat. This way you can leave the temperature higher when you are out and have it lower to a comfortable level just before you arrive home.

Get a ceiling fan. While they will not lower the temperature, fans will do a lot to move the cooler air around the room. This will also let you leave the air conditioner at a slightly higher temperature and use less energy. Leaving the ceiling fan on while you go out will, however not make any difference to the temperatures and will cost you money so best to turn it off.

Think about crosswinds. An easy way to cool the house is to leave a window open. Do not open it all the way, a few inches are enough to cause a draught through the house. This is also a natural freshener for your home. Try to open windows on the opposite sides of the house so that fresh air flows through the rooms.

Think shade plants. The parts of the house that heats up the most are the south and west side. Planting large shade bushes and shrubs will help cool your home down a few degrees.

To sum up

Leaving the air conditioner on all day while you are out does not make a lot of sense. In the long run you will end up paying more for your energy, unless you leave it at a higher temperature. Leaving it on also means that the unit works harder and may need replacing sooner.

Turning the air conditioner on and off seems the better option, particularly if you reduce the temperature gradually when you come home.

Making use of ceiling fans and programmable thermostats is a good idea to help keep your home as cool as you like during the summer months.

One thought on “Is it safe to leave the air conditioner on all day?

  1. That’s good to know that leaving your air conditioner on all day could make it break down faster. I would think that it wouldn’t be worth it to leave it on all day just to have it be cool when you get home. I’ll have to just consider getting someone to install a thermostat that I could program to turn on like an hour before I get home.

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