Very few people buy a major appliance these days without casting an eye over the environmental impact of their purchase. It follows that all manufacturers may a big play out of the environmentally friendliness of their stuff. But what exactly is ecologically sound in electric portable space heaters?
Okay, if you buy good ole USA made electric space heaters then you can be reasonably secure about a few things. It will, for starters, have met quite stringent safety criteria - there are plenty of federal and local laws that US companies must observe. It will also be able to live up to any claims it makes - there are laws against misrepresentation.
So if you buy an electric space heater that claims to be 96 percent efficient, that is good, no? Well yes and no. It means that 96% of the electricity is being turned into heat, which is good. But electricity has to be made elsewhere and transported etc, all of which is not so efficient, and is therefore bad.
The high unit cost of electricity is a reflection of all the losses in the production and is why when put up against, say, propane space heaters, most electrical unit cost more to run.
Then again, if all you are doing is temporarily heating a space, convenience is much more important. Electric space heaters score big on this, so perhaps all you should do is look for the best efficiency rated heater and use it sparingly!