Looking at this as conventional power savings is wrong.
It's better to look at this as comfort. I just recently bought one of those 20 watt heat mats, for one specific reason: while using a computer it is impossible to keep my feet warm. Socks, boots, anything? Doesn't work. It was a huge problem while I was studying.
Since I got one, for 20 W, my feet are warm. In fact, my perception of room temperature as a whole has been massively improved. This is a lot less power usage then any type of whole room solution.
It's better to look at this as comfort. I just recently bought one of those 20 watt heat mats, for one specific reason: while using a computer it is impossible to keep my feet warm. Socks, boots, anything? Doesn't work. It was a huge problem while I was studying.
Since I got one, for 20 W, my feet are warm. In fact, my perception of room temperature as a whole has been massively improved. This is a lot less power usage then any type of whole room solution.