A person installing de-icing cables on their roof.
Frost King
Roof de-icing cables use about 5 watts per foot and a large installation in a very snowy climate can easily add $100 to your electric bill each month.

Roof de-icing kits allow you to harness the power of electricity to keep snow and ice from building up on your roof, but at what cost? Here’s how to estimate how much running a kit on your home will cost you.

Why Use a Roof De-Icer?

If you live somewhere that doesn’t get significant snow accumulation (or snow at all!) then there’s a good chance you’re unfamiliar with roof de-icing kits.

But if you live somewhere with harsh winters, there’s a good chance even if you don’t have a kit of your own, you’ve at least seen them on other people’s homes.

A roof de-icer cable is an electric cable that looks a whole lot like an extension cord. Except the purpose of the de-icing cable isn’t to carry electricity from point A to point B like an extension cord but to serve as an electrical resistor, generating heat in the process—just like the wires in a toaster or electric space heater.

Frost King Roof De-Icer Kit

This all in-on-kit has everything you need, save for a ladder and tape measure, to add de-icing cable to your roof.

You attach the cable to your roof in a looping W pattern along the first few feet above the eaves (as well as down your downspouts, too). When when the snow comes, you turn it on. The cable heats up and melts the snow, clearing it off the eaves.

The purpose isn’t cosmetic—most folks love the cozy look of roofs capped in snow—but instead to protect both the roof, the internal structure of the home, and the home’s occupants.

Snow buildup at the edge of a roofline can lead to “ice dams,” where the heat differential between the warm roof and the cold eave causes melted runoff to freeze right at the edge. Not only can that lead to large chunks of ice that can break free and fall off the roof (causing significant property damage and personal injury in the process), but it can also damage the roof.

An ice dam built up along the gutter of a home.
This thick buildup of ice along your roof is exactly the problem de-icing cables help you avoid. Suzanne Tucker/Shutterstock.com

As the meltwater hits the edge and freezes, it can lift the shingles and roofing membrane up. Then the water can flow freely under the roofing materials and even into the wall cavity leading to drywall damage, structural damage, and mold.

To avoid those problems some people use roof rakes to pull snow off the roof after heavy snowfalls, relying on the sun to warm the roof and finish the snow and ice removal. But depending on the area you live in, the solar orientation of your roof, how much snow you get, and the design and insulation level of your roof, roof raking might not be practical or effective.

How Much Does It Cost to Run a Roof De-Icer?

If you think that it can’t possibly be cheap to use a giant electric cable to melt snow off your roof in icy depths of winter, you’d be correct. It requires a significant amount of energy to melt snow and ice, but it might not be as bad as you’d imagine depending on how often you need to use the system.

Let’s run through a basic estimation, and you can adapt our estimate using our formulas to fit the size of your home, the area you need to de-ice, and your local electrical costs.

How to Estimate How Much De-Icing Cable You Need

How much cable you need depends on how much roof you have and how deep your eaves are. You need enough cable to cover the roof about a foot back, plus whatever the depth of the eave is. So a roof with no eave overhang only needs approximately 2 feet per linear foot to create the zig-zag setback you need.

But for every extra foot of the eave overhang, you should add another 1.8 feet or so to the total cable length. A home with deep 2-foot eaves will need around twice as much cable as a home with no eave overhang.

You also have to account for the downspouts, as it does you no good to melt the water on the roof only to have it freeze solid in the downspout carrying it away from your home. At minimum you’ll need at least as many feet as you have downspout but many people double the wire to ensure enough heat to keep it flowing freely (especially if the downspout leads into a drain run buried beneath the yard).

If you want to plan out a de-icing system more precisely than just a rough estimate, we’d recommend checking out this guide to planning and installing your de-icing cable system from Frost King and this well-written guide from King Electric.

For example, let’s say that you have 100 feet of roofline with a 1-foot overhang (so you’ll need 100 ft. * 2.8, or 280 feet for just the eaves). Add in four downspouts that are 12 feet off the ground with a 6-foot run at the bottom, and you have an additional 72 feet for a total of 352 feet of cable.

Some people choose to only apply the cable to the portion of the roof that gets the least sun or has the worst problem with ice dams, so feel free to adjust your calculations to include everything from the whole roof edge around the entire home to just the part by the back door that gets very little sun in the winter.

Calculating the Cost of Running De-Icing Cables

Now that we have a rough idea of how much cable we’re going to use on our theoretical house, we can consider how much energy it will use.

Depending on the brand and thickness of the cables, de-icing cables use around 5-8W of power per foot of cable. Do note that the power consumption is based on the physical cable length, not the length of the roof edge traversed by that cable. For the sake of our calculations, let’s use 5W because that’s how much the nearly ubiquitous Frost King cables use.

To figure how much total power our cable run will use, we simply multiply the number of feet (in this case 352) by the wattage per foot (5W) to arrive at a total load of 1,760W.

Now that we know the wattage, we can use the same methods outlined in our guide to measuring your energy use to figure out how much the de-icing system will cost per hour of operation.

First, we need to convert the 1,760W operating load into kilowatt hours because that’s how your electric company bills you. So we’ll multiply the load by hours and divide by 1000 to convert.

(1,760W * 1 Hour)/1000  = 1.76 kWh

Then we multiply that value by how much we pay per kWh. Per the U.S. Energy Information Administration’s most recently published stats (featuring data up to August of 2022) the U.S. average kWh cost is 15.95 cents, so we’ll use that in our equation.

1.76 kWh * 0.1595 = 0.28

Our de-icing setup costs 28 cents per hour to operate. Using that information, we can now estimate how much it would cost us based on our projected usage.

Let’s say you’re living in some Day After Tomorrow icy post-apocalyptic hellscape that requires you to run your de-icing cables day and night. It would cost you $6.74 per day and an eye-watering $202.12 a month de-ice your roof with our theoretical 1,760W system.

Using a heavy-duty timer that toggled the de-icer on for 8 hours a day would cost $2.25 a day and $67.37 a month. Speaking of timers, you can also buy thermostat-driven plugs that only turn on when it’s cold enough.

And if, let’s say, you did get heavy snow but it was interspersed with long periods of sunshine that allowed you to run your de-icer during the snowstorm itself but otherwise leave it idle, you’d spend a lot less. If you could squeeze by with only 12 hours of runtime your cost over a given month would be $13.47.

Profile Photo for Jason Fitzpatrick Jason Fitzpatrick
Jason Fitzpatrick is the Senior Smart Home Editor at How-To Geek. He has over a decade of experience in publishing and has authored thousands of articles at How-To Geek, Review Geek, LifeSavvy, and Lifehacker. Jason served as Lifehacker's Weekend Editor before he joined How-To Geek.
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