I've put an ethanol burner in my old non-functioning gas fireplace as the replacement or fixing cost for the old unit costs much more than I anticipated.  Overall, I like the ethanol burner very much as it put out surprising heat and it presents a very relaxing atmosphere.  Having said that, I wouldn't go as far as saying it heats as efficiently as central heating would.  There are some people concerning about the odor.  I'd say it's up the fuel brand you'd use.  I...