In most regions of North America, electric-resistance space heating is expensive to operate. Since air-source heat pumps use only 33% to 50% as much electricity as electric-resistance heaters, most homeowners who want to heat their homes with electricity specify air-source heat pumps.
That said, there may be a good reason to include some electric resistance heat in your home: for example, if your house is very small and well insulated; if you live somewhere with low electricity rates; if your house is equipped with a large photovoltaic (PV) system; if you want to supplement the output of an air-source heat pump on the coldest nights of the year; or if you want to make your bathroom a little more comfortable.
There are many ways to provide electric-resistance heat: you can install electric-resistance baseboard units, electric-resistance wall panel heaters, electric-resistance cove heaters, or an electric boiler connected to a hydronic distribution system. In this article, I’ll focus on another type of electric-resistance heat: electric-resistance cables or mats installed under flooring (usually tiles). The most common place to install this type of heat is in a bathroom.
How much will it cost to run?
If someone in your family likes the feeling of a warm bathroom floor, and you don’t mind the operating cost for a small amount of electric-resistance heating, you may be thinking of installing electric-resistance heating cables under your bathroom flooring. Is this a good idea?
Opinions vary widely on this point. Suffice it to say that electrically heated bathroom floors aren’t a total energy disaster, and many people like them.
How much electricity will it take to heat your bathroom floor? The answer, of course, is “it depends.”
A typical installation draws from 12 watts to 15 watts per square foot. Let’s start with some assumptions: