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Musings of an Energy Nerd

Electric Resistance Floor Heat

A little bit of extra heat for a bathroom floor probably won’t drive your electricity bills to the stratosphere

The key to electric-resistance floor heating is to use it only when necessary. Electric-resistance heating is expensive to operate, but if it's only used for an hour a day in a small room — for example, a bathroom — then using this type of heating system probably won't bankrupt you. [Photo credit: Warmly Yours]

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:

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  1. bob_swinburne | | #1

    Thanks for this - It is notoriously difficult to find energy use information on many of the manufacturers's websites.

  2. user-6504396 | | #2

    A great article as always. This is something we are getting ready to install in the two bathrooms of our new house. I would be interested if others have an opinion on floor versus wall heat sensors and if there is any information out there on the durability of the systems offered by the various manufacturers. As mentioned above, repair is a problem if the system ever fails.

  3. heidner | | #3

    If you add electric heat to the floor, make sure you keep the elements about 15" away from any toilet bowl flange...any seal that uses wax. that extra 10 or 20 degree temp rise by the seal can easily speed up its failure as it causes the wax to soften... and plunging a plugged toilet can blow path through the wax... (based on experience).

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