My roommate and I have noticed that, since our apartment faces south and we live right by the Hudson, our apartment is starting to be quite chilly in the evenings, and oftentimes is cooler inside than out. We haven't started turning on our heaters yet, and yesterday she suggested we buy space heaters as a solution for keeping our (fairly empty) apartment warm enough to read or surf the internet in without having to bundle up indoors or have our window heating units running for extended periods of time. (This gets expensive, and we were able to cut our electric bill by 75% by running the AC for short periods in the evenings alone last month.) Naturally, we would unplug and put away said units before we left for work each morning.

Our current built-in units are Islandaire brand under-window units, EZ Series, 42. We haven't picked a space heater yet, but chances are I'd just pick one up from Target.

  • Any reason you could not just run your window heating unit for short periods of time (however long you would be running a space heater)? If they are both electric heaters I don't really see how one is going to be much more efficient than the other (unless the window units are in the "wrong" room).
    – auujay
    Commented Sep 19, 2011 at 16:26
  • We have one in each room. I guess I'm really asking for a larger pro/con answer. That said, given that I'm usually in one specific corner of the living room, or in a certain corner of my bedroom, I'm wondering if a space heater wouldn't be the better option.
    – Aarthi
    Commented Sep 19, 2011 at 16:56
  • I'm with auujay on this, unless you're heating a smaller space with the space heater, I don't see it being any more efficient. So unless you wall off your designated "warm corners," I'd stick with the window unit, but turn it off/down when you don't need it. Can you connect this to a programmable thermostat?
    – BMitch
    Commented Sep 19, 2011 at 19:15
  • Alas, I cannot, though oh, how I wish I could. I miss central air/heat, like I had in my university apartments/dorms. Heck, even the crappy radiators in the older buildings would actually be preferable. If the space heater wouldn't really be more efficient, then that's really the answer I need. I can turn on/off my window unit when the "cycle" finishes to keep it from busting, but keep it turn on (just low) in the dead of winter.
    – Aarthi
    Commented Sep 19, 2011 at 19:26
  • 1
    The more thermal mass you can put in your apartment, the more you'll retain heat into the night. (You'll take longer to heat it up again during the day, but most people aren't home during the day.) Bookcases against the outer walls are particularly effective as they both provide mass and insulation. Commented Sep 20, 2011 at 14:04

1 Answer 1


Looking at the unit you linked to (and your comment on waiting for the "cycle" to finish), it appears to be a heat pump. Heat pumps are typically more efficient than electric radiators (e.g. a plug in space heater). They lose efficiency as the outside temperature falls, and eventually you should switch over to emergency or electric heat, which should be built-in to this unit. This is identical to the heat source you would have with a space heater. I doubt you'll see more efficiency out of a space heater (it all depends on the individual units), but if you do, it wouldn't be until it's very cold out.

Side note: The point to switch to electric heating is somewhere around the freezing temperature. I've seen comments ranging from 40F to 20F, that that may also vary from one unit to another. Depending on the unit, this switch may be automatic, or you may have to manually enabled it. If you get down to freezing outside and can't get above 65F inside, then I'd manually flip to electric heat.

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