I moved into a studio apartment in a commercial building turned residential. It has this kind of heater—

enter image description here

—which I believe is an electric air heater. It's loud as hell.

Everything I'm reading says oil-filled radiators are far more cost-efficient for larger spaces, despite being slower to the heat the room (which I don't mind).

So I had 2 questions, actually.

  1. Are there any caveats to running 1 or 2 high-capacity oil-filled radiators? Like safety concerns, especially considering the apartment is equipped with a sprinkler system as also shown in the photo. (Is a building fire + oil-filled radiators + cold water potentially extra, extra bad?)

  2. I'm just curious, why would cost-conscious businesses want to use the kinds of heaters pictured, on top of all the noise? Why did commercial buildings opt for them instead of oil-based tech in the first place? I don't imagine quick warmth and comfort for industrial employees would have been the reason.

  • Do you know how much HVAC load (in BTUs) you're up against with this space? Also, are you in a situation where air conditioning would be desirable, and what sort of worst-case low temperatures do you have to deal with? Jan 23, 2021 at 4:02
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    It looks like about 50,000 BTUs according to an online calculator. I didn't even think about cooling... does that thing do cooling too?! I'm in New York, so 10 or 20 below to human body temp. Jan 23, 2021 at 4:12
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    That's gas fired and high efficiency. No AC coil. Hopefully there's a filter rack somewhere. You're probably reading about oil space heaters (which are awesome; I have one under my desk), not to be confused with unit heaters (which is what it would have been or was), nor furnaces (which is what that is), nor air handlers (forced-air 'furnaces' w/o heat), nor split system AC - both parts of which you lack: the coil inside and the condenser outside.
    – Mazura
    Jan 23, 2021 at 5:10
  • Yup, there's a filter on the intake. And "under my desk"—actually, that's a great application despite high ceilings—I may do that. Jan 23, 2021 at 5:33

2 Answers 2


Well, first off, you're wrong about the heat source.

See the gray insulated pipes?

Those are carrying hot fluid from (and cooler fluid back to) a source that costs a LOT less than electric resistance heat.

That flows through a coil, and a fan blows air through the coil.

You have a fan-coil unit.

Or, possibly, those only carry chilled water for cooling in summer, and the black iron pipe carries natural gas to the unit - again, much less costly than electric resistance heating. That would be a "Gas unit heater" though I can't see where the exhaust is if that's the case. OK, based on comments, the gray pipes appear to be intake and exhaust for a "sealed combustion" high efficiency condensing gas furnace.

So, oil-filled (or any other kind of) electric resistance heat will cost a great deal more to operate.

Noise may be able to be reduced somewhat, but is generally not a major consideration for industrial heating, and strong air movement is required (with associated noise) to distribute heat in a high-ceilinged space like that. Your oil-filled radiators would give you a nice warm ceiling. The warmth might not even reach your head level.

If the "conversion" from industrial to residential was as minimal as this implies, you probably have a much larger heat load than you would expect. Such factory buildings were insulated somewhere between minimally or not at all, when built. There was penty of excess heat available from steam power needed for industrial processes, and fuel was cheap.

  • Wow. I did not expect such a definitive answer to not get oil-filled radiators. I can totally imagine warm ceilings now. I'm really glad I asked, thank you. Jan 23, 2021 at 4:19
  • I worked in one of those spaces before it turned excessively residential (I rented "workspace - 24/7/365 - some folks are living in their studios but that's not actually permitted" I left after there were complaints from the illicit residents about me actually using my tools in my rented workspace.) I'm a bit familiar with old mills.
    – Ecnerwal
    Jan 23, 2021 at 4:24
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    Yellow thing is a condensate pump. White pipe appears to be leading to it. That might imply that you have an efficient, "condensing" furnace, or it might be just for condensate from the presumed cooling function. Gray pipe configuration is not suitable for exhaust.
    – Ecnerwal
    Jan 23, 2021 at 4:40
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    Actually, I guess it is possible, if that's a window / outside wall rather than an internal passageway that the gray pipes lead to, it COULD be a "sealed combustion" setup where air is drawn in one pipe, and the (rather cool) exhaust goes out the other pipe. Picture is far enough away that it's hard to be certain - I took them for insulated fluid pipes - and they might be. But they could be intake/exhaust for that type of gas furnace.
    – Ecnerwal
    Jan 23, 2021 at 4:50
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    Aw, man. I just stuck my head out the window and yea, they're both cut open at the window. I was hoping for cooling in the summer. I see. Is it possible that this building at one point did use a fan-coil unit, but then renovated and repurposed those pipes? So maybe it's both. Jan 23, 2021 at 4:54

@Ecnerwal 's answer is right on the money: You have a fairly new high efficiency gas forced air heater, and except for the noise it is a pretty good setup.

But a little note about the magical "high-capacity oil-filled radiators". Most of the time these are yet-another variant on electric hair dryers heaters. Seriously. The standard cheap electric heaters - whether purely radiant (see the glow), forced air (fan included), oil-filled, ceramic, whatever... - are in the end all a ~ 1,500 W electric resistance heating element. That's it. There are various ways to help distribute the heat (fan goes the farthest), prevent super-hot spots (oil works well for that), etc. But in the end, you would (except that they last a little longer) get the same amount of heat by turning on a standard $ 20 hair dryer. Nothing magic, no matter what the advertising claims.

There are bigger/better electric heaters, but until you get to the world of heat pumps, they are really just bigger variants on the hair dryer. A 30A 240V electric heat system, unless it is a heat pump, is essentially the equivalent of 4 hair dryers.

That being said, electric space heaters do have a use. They are particularly helpful when you don't have a nice big gas forced air heating system or if you do but due to circumstances beyond your control (big office or apartment building where you can't control the thermostat) you want to add supplemental heat in specific areas. But for overall heating, natural gas works better/cheaper.

(Except if it quits working, as it did for me today, but a power-cycle reboot worked, fortunately.)

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