Here's a thought:
If you're looking for something for permanent installation that is quiet, low wattage, and runs off 110/120:
You might take a look at
King baseboard heaters. These are ceramic-filled baseboards- no water/oil for thermal storage. You can buy them in 120v and as little as 250 watts....length determines wattage in this case. I bought a 3-footer for use in my (very small) trailer. It's 500 watts and used under my dinette table it's sufficient to take the chill off.
A bigger space might call for the strategic placement of several of these, all running off a single circuit (depending on heater size). Certainly a good way to "distribute" the heat...
The price of the Envi you're looking at equals the cost of three of the
500 watt King I bought.Proud Side Note:King Manufacturing is based here in (King County) Washington, and- rarest of rare things- ALL of its heaters are made right here in the U.S.of A.!