how long can a space heater be left on running

How long can you leave a Space Heater on?

How long can you leave a space heater on? Will space heaters eventually catch flames? Or will they break? In this article, we are going to explore these questions. After reading this, you’ll be confident and able to use your space heater responsibly.

Quick answer: All quality space heaters theoretically are safe to run 24h a day. As long as you are in the same room, you can leave a space heater on. Modern space heaters have built-in safety features such as a temperature controlling thermostat, tip-over protection, and overheat protection, which reduce risk of fire.

This is not only a question about safety. But other factors also become part of the equation. For example, when you run a space heater continuously, how much will it cost you?

And will the space heater break soon when you run it 24/7?

Let’s have a look.

How long can you leave a space heater on?

All quality modern space heaters are designed to run for long periods of time. Many people use space heaters as their primary source of heat. Heating just individual rooms, instead of the entire house saves them money.

Here, I emphasize the terms quality and modern. With quality, I mean that you should use a heater that has a solid appearance and is made of good and fireproof materials. Some cheap supermarket space heaters are made completely of low-quality plastic. These cheap materials wear down quickly and sometimes even melt.

When you run a space heater for long times, its surface temperature increases. That’s why you want to have a solidly built product.

Aside from the build quality of the space heater, it is also important that your space heater is relatively modern. Space heater technologies evolve rather slowly. So, you can consider anything that is younger than 10-15 years as modern.

The reason is that modern space heaters come with several built-in safety features which greatly improve their reliability. The most important reliability feature is overheat protection. Overheat protection turns a space heater off when it becomes too hot.

This means that even though your space heater runs for long times, it is never in danger of overheating and causing a fire.

A high-quality and modern space heater can be left on 24h a day. It should come with several safety features that prevent disaster and should be made of fireproof material.

The space heater I would personally trust to run for very long periods of time would be this De’Longhi oil-filled radiator (click here to see it on amazon).

Can you leave a space heater on at night?

If your space heater is of good quality and has all the necessary safety features, you can leave it on overnight without worry.

It is important that your space heater has built-in overheat protection and a thermostat that keeps the temperature at a set level. These two functions ensure that the space heater never gets too hot.

Aside from that, I would suggest you make sure that small children or pets in your house can access the space heater at night. Either you should place the space heater in a safe, inaccessible place. Or you should ensure that children and pets can’t access your bedroom at night. The reason is that while you sleep, children and pets can burn themselves on the heater.

But, yes, technically you can leave a space heater on at night.

Leaving a space heater on overnight is, however, not in all cases the most cost-effective decision. Financially, running a space heater at night costs you significant money without you even noticing the heat most of the time. So, is it really worth it to run your space heater overnight?

That’s a personal decision.

But my personal suggestions would be to save the few bucks in electricity cost each night and go with a hot water bottle in your bed. Or you can program your space heater using the built-in timer (if it has one).

Alternatively, you can buy a wall outlet timer to program the times at which your space heater runs. In case you are interested in that, check this article about using a space heater with a timer (click here to view it).

Which space heaters are the safest?

There are thousands of different space heaters available online. How do you know which ones are best suited for running long times?

Generally, for long, reliable and safe usage, oil-filled radiators are the best type of space heaters. Oil-filled radiators consist of a big oil-filled metal body. Inside the oil, there is an embedded electric heating element.

The oil carries the heat from the heating element to the large metal surface, which consists of many chimneys that exchange the heat with the surrounding air.

Because of this effective heat distribution concept, oil-filled radiators never reach large surface temperatures. Yet, they heat rooms just as well, if not better than other types of electric space heaters.

Oil-filled radiators rely on distribution of heat, which makes them exceptionally durable. No single part of the heater is exposed to high temperatures. Also, there are no moving parts in the space heater, such as built-in fans or a rotating axis.

The distribution of heat and the absence of moving parts makes oil-filled heaters the most durable type of space heater since there is no part that wears down quickly.

You can only break an oil-filled radiator by force. It is very unlikely to break on its own. Just until recently, we had a 30-year-old oil-filled radiator in our house, which worked perfectly fine, even when we discarded it.

If you want to have such a safe, reliable, and durable space heater as well, I advise you to check the oil-filled radiators in my article about the 3 best space heaters you can leave on all night (click here to view it).

When you should always turn off your space heater

Now, even when your space heater is well built and has all the needed safety features, you should not always leave it running.

Most space heater accidents happen when nobody is at home. Even though space heaters are generally safe to run for long periods of time, unexpected things can happen around a space heater.

First and foremost, space heaters are electronic products. Nobody can guarantee that they run without failure. And second, the surroundings of a space heater might be the cause of a disaster. It could be that thin curtains catch flame. Or a lighter refill propane bottle near the space heater heats up and explodes.

That’s why you can’t rely on your space heater only. You have to make sure its surroundings are safe as well.

And if something ever goes wrong, there needs to be someone who is able to stop the disaster:
Never keep a space heater running in your absence.

As long as you are in the same room as the space heater, nothing can happen. If the space heater fails and catches flames, you can extinguish the fire. But if you are absent, you will return to a burnt-down home, a dead pet, and lifelong debt and guilt.

Can you trust a space heater to run reliably for long periods?

Another question that might be relevant to your question is: How much do you worry?

In the previous section, we have seen that it is perfectly safe to run a space heater for many hours without interruption. In extreme cases, you can even run them for 24h a day.

As long as your space heater has all the required safety features (overheat protection and thermostat), and as long as you are in the same room as your space heater while it’s running, you can leave it on as long as you want.

Still, running your space heater all the time does not always make sense. It also depends on your personality.

Are you a confident person who trusts the space heater to run without issues? And if something goes wrong, do you know how to extinguish the flames? Are you clear-minded and quick to take action? If you can answer these questions, running a space heater 24/7 is no problem. You trust the space heater, but you are still aware that if something happens, you know what to do.

The other personality type is the insecure person. I think most people are rather insecure. If you are the kind of person that doesn’t trust a space heater to do its job, that’s not good.

Also, if you are not confident that you will react calmly if something happens, you should not leave the heater on for too long.

Insecure people who don’t trust the heater and its safety features should only leave their space heater on as long as they’re comfortable. When you are such a person and feel like the heater is getting too hot (even though it has built-in overheat protection and a thermostat), then you should switch it off and let it cool.

It is not about actual danger. But more about your psychological wellbeing. Never do something you are not comfortable with. You will always have the space heater in the back of your head and you won’t be able to calm down.

Only leave space heaters running when you are comfortable with it. As soon as you start worrying, turn it off. Oftentimes, a little too much worry is better than acting overly confident.

The cost of running a space heater for long periods of time

Running a space heater costs money. In another article about space heater electricity cost (click here to view it), I have done extensive research and calculated how much an average space heater costs you per month.

The electricity cost of a space heater depends on how much watts of power it draws from the wall outlet. An average 1500W electric space heater costs you $43.20 per month at a rate of 12 cents per kilowatt-hour. 

However, this result was calculated for 8 hours of daily usage. Since a day consists of 24 hours (24 = 3 times 8), the monthly costs for running a space heater continuously 24h a day will be $129.60.

Running an average space heater 24/7 costs you $129.60 a month.

When will a space heater break if you leave it turned on?

Space heaters are electronic devices. This means they will eventually break down. Will running them continuously lower a space heater’s life expectancy? Let’s have a look.

While the previous sections dealt with the question: “How long is it safe to leave a space heater on?”, this section is about “How long can a space heater run continuously until it breaks?”

An average space heater will last you approximately 15-20 years with regular usage. That’s quite a long time. Let’s just say we have a space heater that lasts 16 years.

The average daily heating time over 16 years is 1h a day. In the summer months, the heater is not used, in the winter times a little more. The heater is placed somewhere and forgotten. Then it is reused for a garage workshop, or something similar. That’s the typical lifecycle of a space heater. It results in 1h average daily use.

This means in one year, the heater runs for 365h.

16 years multiplied by 365 yearly hours is 5840h of total lifetime.

Now let’s assume instead of running the heater for 1h a day, you run it for 24h a day.

5840 hours of total space heater lifetime divided by 24h a day equals roughly 243 days of continuous usage.

However, the 5840 hours of total lifetime assumes that the heater has a cool-down period every hour.

Let’s guesstimate that the cooldown times increase the longevity of the heater by a factor of 4.

This means a regular heater would wear down after 60 days (2 months) of continuous usage.

Of course, this is just a very rough estimation. I am sure, some cheap space heaters break down after a day or two, while others run for months or even years.

It all depends on quality.


As long as you trust your heater, you can leave it on 24h a day. Just make sure you place it in a safe place where it can’t ignite anything. Also, make sure to always turn the space heater off when you leave the room.

Then, you are safe.

About the Author

Daniel Hirsch

Daniel is an electrical engineer, blogger, and author. He studied electrical engineering and information technology and decided to blog about heaters after working in the temperature sensing industry.