About a year ago I wrote about the convection wall heaters that I installed in my home's "Three Season Room." That piece has generated a lot of views and email, so I thought I'd follow-up with the latest information. You can read the original post here: Convection Wall Heater
The heaters performed well all last winter, and were left on almost every day, all day, for the whole winter. I didn't notice a change in my electrical bill, other than the usual increase that comes from having to run the furnace. Whatever it cost me to run the heaters, it was lost amongst the larger charges.
Without the heaters, the air temperature in the unheated, uninsulated room is usually about 10 degrees above the outside temperature. With the heaters turned on, I found that the room was about 20-25 degrees higher than outdoors. So, unscientifically, I'd say the heaters added about 10-15 degrees of heat.
I'm satisfied with that, it meant the room was usable, but not especially warm, for most of the Chicago winter. However, I still had to be careful about storing freezable items out there on days when the temperature was 15F or lower.