Can I Use an Electric Water Heater for Space Heating?

Infloor heating is great, but justifying the cost of a boiler to make the hot water can be tough, especially if you only plan to heat a small space. Read my answer to a subscriber asking about an option that many professionals mistakenly say is a bad idea.

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Q: Can an electric, tank-style water heater work for space heating with hot water in a radiant infloor installation? My wife and I are building a retirement home in northern Ontario, Canada and we’re sorting out our options. There’s no natural gas available in the area, so we’re looking at propane or electricity.

A: There are several things to consider, but yes, a heavy-duty electric water heater or propane water heater can be used to deliver hot water to infloor systems and radiators. I’ve seen both work well. That said, propane offers an advantage you might not have considered. When the grid goes down you’ll need a very large generator to provide enough electrical power to keep you warm. Propane, on the other hand, offers you a large reserve of energy right on your property in the tank. It only takes a small generator to provide the electricity to run a propane system because the power is only needed to operate the control system and the circulation pumps. That said, you might consider having both propane and electric systems for heating, and the reason is a complete surprise to most people.

Assuming a price of 15 cents per kilowatt-hour for electricity (that’s what I pay in northern Ontario, Canada), any propane price higher than about 90 cents a litre (about $3.40 per US gallon) is more expensive per unit of heat delivered to your home than electricity when run through a propane boiler with an 85% efficiency rating. I know many people who pay more than 85 cents for propane and don’t realize that it’s costing them more to heat than if electricity was used in baseboard heaters or a water heater. Given the relatively low cost of an electric water heater, you might consider having both propane and electricity as options for heating. Propane prices often spike up higher than 85 cents per litre, while electricity costs are much more stable. Having a dual system allows you to use the least expensive option at any given time, plus it gives you more reliability. If one system breaks you’ve got the other until repairs can be made.

Another thing to consider is an electric heat pump instead of an electric tank-style water heater. Models are available that harvest heat from cold winter air, and concentrate that heat in water for heating. Heat pumps generally deliver 2x to 3x as much heat energy as they consume in electricity, and this corresponds to an equivalent propane price of just 45 cents per litre ($1.79 per US gallon) or less.

Watch the video below for a technical tour of this option.

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