Space Heaters

Most common myths about electric space heaters

Luka on November 24, 2022

There are some myths about space heaters which are spread over the internet every year when the heating season starts. Judging by the comments on sites and social networks, it seems that a lot of people believe them to be true.


Most common myths about electric space heaters

While writing this story, I've searched for other articles on this topic and was very disappointed to see authors writing about debunking some energy efficiency myths and actually stating some of the myths are true.

Some even go so far to claim manufacturers of cheap heaters created this conspiracy that all electric heaters are equally energy efficient.

You can imagine how surprised I was to notice they also sell certain types of products.

Oil heaters are more energy efficient than other space heaters

This myth is repeated over and over again every heating season.

Oil filled radiators, fan heaters, ceramic heaters and convection heaters are all equally energy efficient. They are all electric resistive heaters. They take electrical energy and convert it into heat, which means there’s zero waste. Two heaters with a real power of 1.5 kW will produce 1.5 kW of heat that will be dissipated into the environment.

Oil radiator electricity consumption measured with wattmeter
There are many differences in the way the heat is distributed (i.e. radiation, convection), and how we perceive the heat they produce, but it doesn't change their energy efficiency.

Oil radiators are factory filled with diathermal oil that heats up and retains heat for some time after you switch it off. People mistakenly believe that because of this, there's some magical process within that oil that created that extra energy.

Yes, oil heater will radiate heat for some time when switched off, but it also took it that same amount of time to heat up while a fan or convection heater would start warming up the room right away. Oil in the radiator is only used as a buffer to store energy.

It's also common for oil radiators to be marketed as retaining the heat for a long time after switching off. In reality, that long time is about 10 minutes, depending on the size of the radiator. An award for the most comical statement goes to the manufacturers that say oil radiators, unlike other space heaters, don't require continuous supply of electricity to run, which can result in lower electric bills.

Sure, you might prefer a radiant heat more than the hot air being forced throughout the room, but that doesn't change the fact that it's the same amount of heat.

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Advanced aluminum X-shaped heating elements are more efficient

Heating elements in space heaters are designed with metals that efficiently convert electrical energy to heat, typically nichrome, which is also resistant to corrosion at a high temperature.

Some heaters come equipped with aluminum X-shaped heating element that has a heating efficiency of over 99%. What a surprise, it's equally efficient as a standard heating element.

While the percentage of efficiency of each heating element made out of different materials may differ, it's highly debatable what that percentage is. The level of efficiency should be measured by an independent lab with high accuracy instruments and processes.

It's true that depending on the design and materials used in a heating element, it's effective value of current and real power decrease as the heating element gets hotter and it's ohmic resistance increases. But if a low quality heating element's real power decreases with time, it also means that it consumes less electricity - thus making it equally energy efficient.

Advanced space heater thermostats save energy

Sure, not all thermostats are equal and have the same levels of accuracy. In fact there are some really bad ones.

Oil radiator thermostat

Manufacturers often say that inaccurate thermostats won't keep the room at a precise temperature which will result in wasted energy.

But if a thermostat isn't accurate enough and produces some more heat during each cycle, is that energy really wasted? Of course not, the extra heat stays in the room and it'll take longer for the thermostat to notice a drop in temperature to turn on and do another heating cycle.

Now, an inaccurate thermostat might make you feel slightly too hot or too cold if it's operating differential is really high, but efficiency-wise, average energy consumption is the same for cheap and expensive thermostats.

Bigger heaters with bigger heating elements produce more heat

We would all wish this was true. So would hundreds of engineers that came up with an idea to create an exceptionally large heaters that run on only 200 W of power.

If this statement was true, we would need to rewrite some laws of thermodynamics, and no one would have large heating bills.

Underfloor heating is a great example, as it heats a large surface with lower temperature. But guess what, the household still needs the same amount of watts per cubic square feet or cubic metre.

Fan heaters are more economical because they heat the room fast

If a space heater has a fan to help distribute the hot air around the room, it just means that the heat will spread out faster, but since the fan needs electricity to run - that will make fan heater less energy efficient than other space heaters.

Because of the thermal equilibrium principle, no matter where the heat in a room is produced, it'll eventually spread out to the rest of the room. In reality, because of the heat loss, you might use a heater in one corner of a really large room and feel cold in an opposite corner. However, that doesn't change the principles of thermodynamics.

Fan heaters and air conditioners only heat air, not walls and objects

Oh come on! Yes, AC units and fan heaters blow hot air, but that doesn't mean that the objects won't get heated by that hot air.

Regular central heating radiators partially work by convection too, which means they're heating up the dense, cold air from the floor of the room. Warm air heats up people, walls and objects.