Space Heaters

Are Oil Filled Heaters Cheap to Run?

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We all like to stay warm during the winter. Being in a cold room is terrible for your health and makes you less happy and productive. Sometimes heating the whole house can be expensive, so many people turn to space heaters.

If you heat only one room or one part of the room, you will spend less money than you would if you kept the whole house warm. Many types of space heaters on the market, but many people like oil-filled space heaters. This leaves us wondering – Are oil-filled heaters cheap to run?

Your oil heater’s cheap or expensive will depend on your area’s electricity rate and the amount of power your space heater uses. The US’s average electricity rate is 10.42 cents. Most oil heaters use 1500 watts of power. So, going off this, if you run your heater for 8 hours every day, it will cost you roughly $25 a month. 

Although this price might seem expensive, you have to consider that your space heater won’t be on full heat for 8 hours. Oil heaters have a thermostat that helps them regulate and maintain the temperature in the room.

Oil heaters maintaining temperature means that it will only heat up once; after that, the heater will only turn on to maintain the temperature. Keep reading to find out how oil-filled heaters work and how to calculate the cost of your oil-filled space heater. 

How Does An Oil-filled Heater Work?

Oil-filled heaters look like radiators but are smaller. It is portable and comes on wheels. Oil heaters are also filled with thermal lubricant and use an electrical part to heat the thermal oil inside the heater.

This electrical part sits wholly submerged in the oil, and when it heats up, it transfers that heat to the oil. Unlike most heaters, you can install oil-filled heaters anywhere in the house. They are versatile and only need electricity to work. 

Many people don’t know the difference between oil-filled heaters and central heaters.

  • Oil-filled heaters have their internal heating part, which heats the oil inside them.
  • A central heater is just a shell that uses hot water in pipes to produce heat. Central heaters rely on many lines and water, but oil-filler heaters only rely on electricity.

The space heater’s body is made of a set of stacked columns made from metal. The bigger the surface of the heater, the more it will come into contact with air. If you have a bigger space heater, it will heat your air faster.


That being said, how big your space heater is has nothing to do with how much heat it will produce. This depends on how much energy the space heater consumes, which measures in watts (W).

The more watts a space heater has, the more heat it will produce. That does, however, mean that running a heater with more Watts is more expensive

No Fans Involved & Built-in Thermostat

Oil-filled space heaters don’t have a fan, which is why they are so popular. They are reticent, and you can use them in any room. Another reason many choose this type of heater is because it has a built-in thermostat.

Once the room air reaches a specific temperature you have set up for, the heater will turn off. It will turn back on when it senses that the temperature has dropped below your preferred temperature. 

As already mentioned, oil-filled heaters have a heating element inside of them. It is a simple coil made out of metal-resistant wire inserted into the base of the oil-filled heater.

When you turn on the oil-filled heater and the electricity starts running, the electrons bundle together and move through the wire. In return, it creates friction, which results in heat. The cables heat the thermal oil.

This heat transfers to the heater’s exterior, and that’s how oil-filled heaters heat the air. Even though the shapes and sizes of oil-filled heaters vary, the way they work is always the same.

Two Different Types Of Oil-filled Heaters

There are two main ways a space heater can heat its surroundings. 

1. Radiant Heaters

Radiant heaters generate infrared radiation. Everything on Earth radiates in a way that is proportionate to its temperature. Radiant heaters produce infrared radiation in the form of electromagnetic waves.

These waves are invisible and get absorbed by the objects surrounding the space heater. These heaters don’t heat the air; they heat furniture, people, clothes, and anything in their way. 

2. Convection Heaters

The oil-filled heater is a convection heater. Convection heating is when a hot object is placed into a liquid or air. The molecules that are in direct contact with objects heat up and expand.

As they expand, they move away from the objects and move the cooler air molecules under them. These colder molecules then have to drop down and come into contact with the heat source.

They get warmed up, expanded, and replaced with the colder molecules above them. This whole cycle continues to keep the air warm.

Air isn’t an excellent heat conductor, so these heaters take longer to warm the room up. Some other convection heaters are water, ceramic, fan, and furnaces.

No Oil Refills Required

Many people think that oil-filled heaters work the same way as propane heaters and have to fill them with oil all the time, so they decide against buying them.

However, there is a sealed casing around oil-filled heaters, which means that the oil on the inside can’t get out, and you can’t add any oil.

Don’t worry about the oil burning. It doesn’t evaporate, so you do not need to refill it. The oil can get out only if your space heater is broken. 

If you do have to refill the oil, make sure you get a professional to do this. You can use any thermal oil and fill your space heater as much as you want.

Some manufacturers use mineral oil, and others use engineering oil or oil with a unique formula. If you put the wrong oil in your space heater, you can cause much damage.

You wouldn’t put the wrong type of gas in your car, so why put the wrong oil in your space heater. There always has to be an air gap in the reservoir, so the oil has someplace to expand when it gets hot.

Why Diathermic Oil Is The Best Choice

There are two reasons why diathermic oil is the best choice for an oil-filled heater.

  • It has a high specific heat capacity
  • Because it has a high boiling point.

This means the oil can get pretty hot before it starts boiling. You don’t want your oil to burn because if it does, it will turn into vapor, and you would need an additional high-pressure system to contain all the volume.

The space heater doesn’t need any other complicated equipment due to the diathermic oil not reaching a boiling point while heating.

Thanks to its high heat capacity, the space heater will still produce heat even if you turn the electricity off. This is because the oil will need some time to cool off. 

Best Place To Put Your Heater

The best place to put your oil-filled space heater would be in the center of the room. This way, the air will be able to circulate evenly throughout the whole room.

If you plan on using your oil-filled space heater in a part of your open-plan home, you’ll need more than just one space heater.

You should also remember that, while rooms with doors can contain heat better than open ones, the heat will escape from your room if you keep opening and closing the door.

Don’t place your heater near the door, even if it is closed. The heat will escape the room before it can circulate the air and make it warmer. 

Remember that oil-filled radiators aren’t the safest on the market. They don’t glow, but they can get boiling. It would help if you kept the oil-filled space heater at least 3 feet from all flammable materials, such as clothes, bedding, furniture, drapes, etc.

It would be best never to leave your space heater on the carpet because that increases fire risk. You should always keep your oil-filled space heater away from water sources.

Most importantly, make sure you never let a child or a pet touch the heater while it’s on because it can get quickly burned.

Do Oil-filled Heaters Use A Lot Of Electricity?

Most oil-filled space heaters today use 1500W of power. You can also find some smaller ones which use 700W of power.

How much electricity your oil-filled space heater uses depends on its use. You can lower the amount by simply reducing the temperature that you want to achieve. 

It might be hard to imagine how much 1500 W of power is. You use about 1500W of power when using two vacuums or three desktop gaming computers simultaneously.

You might think that’s too much and opt for a different type of space heater. However, you are unlikely to find a separate heater that uses less than 1500W of power.

Almost all space heaters use 1500W of power because that’s the maximum amount of energy you can get from a wall outlet. This way, manufacturers produce the most effective heaters. 

Since most heaters use the same power, the best choice would still be to get an oil-filled heater. It comes with a reliable built-in thermostat and is much better at controlling the room temperature than other heaters.

A Few Ways To Lower Energy

This is why many people notice that their electricity bills decrease when they use oil-filled space heaters. There are also a few ways to reduce the energy your oil-filled space heater uses. 

Since the heat generated by an oil-filled heater is easily carried away, it won’t work well in uninsulated rooms. Ensure you get proper insulation or use this space heater only in insulated rooms. 

Setting the thermostat to only one degree more minor will use about 4% less energy. You could also try wearing warmer clothes to keep your space heater on as low as possible. 

How Much Does It Cost To Run An Oil-filled Heater?

Since almost all oil-filled space heaters use 1500W of power, we will consider that amount of energy. We know that the average electricity rate in the United States of America costs about 10.42 cents per kWh.

Running your oil heater for roughly 8 hours per day would cost approximately 83.36 cents per day. If you time that by 30 days, you’ll add an extra $25 more to your electric bill during the winter months.

How much it will cost to run your oil-filled space heater depends on the cost of electricity in your area and your space heater’s power consumption. The power consumption will be written on the heater or the box it came in, but you can look it up online if it isn’t. 

Using your 1500W oil-filled space heater will cost you about the same as using your regular central heating radiator. 

How Efficient Are Oil Heaters?

Many people think buying a branded product will be more efficient, but that’s not true. You can sometimes even pay up to 50% more when purchasing a brand-name product to get a product with the same features and is similar to a cheaper product. Whether or not you get a brand-name space heater doesn’t influence how efficient it will be. 

However, where you put it is something that significantly impacts your oil heater’s efficiency. Every heater has a specific location where it performs the best. Infrared heaters work best outdoors, while an oil heater is useless outside.

Oil heaters are the most efficient at warming large, closed rooms for more extended periods. Oil heaters produce heat that feels more natural because it warms the air rather than infrared heaters’ objects. 

Almost all oil heaters have a built-in thermostat that works much better than other space heaters. A thermostat on an infrared heater wouldn’t be handy, as it can’t determine the room’s temperature because it doesn’t warm the air.

However, the thermostat on an oil heater can sense the room’s temperature while considering your preferred set temperature. 

Which Type Of Heater Is The Cheapest To Run?

The cheapest heater to run would be the infrared space heater. This is because it doesn’t heat the air; it only heats the objects surrounding it. This means that you can put the heater next to a couch while watching TV, which will keep you warm while the rest of the room is cold.

This is great for when you won’t move around much, like when you’re working. Since the heater is only heating one specific spot, it saves you energy.

Infrared heaters are more expensive than other heaters when you buy them, but they make up for it when you use them.

That being said, you shouldn’t choose your space heater based on the price but based on its features. Infrared heaters might be the cheapest to run, but they won’t do much for open-spaced rooms, gyms, kitchens, and other rooms where you move a lot. 

Final Thoughts

To summarize everything, oil-filled heaters can be cheap to run depending on how long you have them on and where you are currently using them. Always ensure you are doing the best you can to save money on your electricity, and you’ll have the warmest house in your neighborhood!


Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.