I would say this is on topic.  Lots of us use electric heaters to supplement.  Much cheaper than Propex :)
My two cents from a guy living in -30 weather:
Electricity is 100% efficient (or close) regardless of the fixture, but it may or may not be price competitive with less efficient heaters that use different fuel.  I think?
I prefer radiant heat - much more comfortable and stable.  And quiet.  I would think the nasty fan on some electric heaters must consume extra power too.  Love my oil filled unit.
Jeff
> Date: Mon, 9 Dec 2013 07:59:19 -0800
> From: camping.elliott@GMAIL.COM
> Subject: [OT] Efficiency of electric heaters?
> To: vanagon@GERRY.VANAGON.COM
> 
> Hi all,
> 
> (This is not Vanagon-related but I don't know another pool of engineers
> and scientists to write to, so I'm writing here for help.)
> 
> It's pretty cold here in Bend, Oregon, and the house that her son is
> renting is colder than he'd like. It's an older house, built cheaply,
> and only has electric baseboard heaters -- no gas, no fireplace.
> 
> Mrs Elliott has been looking at electric heaters and asks whether some
> put out more heat than others. "1500 Watts is 1500 Watts, same BTUs" I sez.
> 
> I sez, "It doesn't matter whether the heating elements are fifteen
> one-hundred Watt light bulbs, or whether the heating elements are put in
> an oil bath; it doesn't matter whether they write the words `infrared'
> or `quartz' on the enclosure: you'll put the same heat into the room.
> All heaters are alike in terms of heat output.
> 
> "Sure, an infrared heater can be `aimed' directly at your body, which is
> real nice; and others have blowers that can direct the heated air and
> stir the air to keep the colder air from pooling on the floor, but in
> terms of how warm the overall air in the room eventually gets, all 1500
> Watt heaters are the same."
> 
> That's what I sez. But she knows I'm a bit of an idiot sometimes and is
> tempted by expensive 1500 Watt heaters, thinking there must be a reason
> why they promote this quartz or that oil-filled feature. She points out
> that when you turn off an oil-filled heater, it still radiates heat for
> quite some time afterwards; I point out that the slow cooling is matched
> by slower warming.
> 
> Can the engineers and scientists in the room comment on this matter? So
> that This Marriage Can Be Saved? If I'm wrong, I'm wrong.
> 
> (Probably don't want to clutter up the list with this, please email to
> me directly.)
> 
> --
> Jack "Rocket j Squirrel" Elliott
> 1984 Westfalia, auto trans,
> Bend, Ore.