How much do roof thawing kits cost?

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 prevent snow and ice from building up on your roof, but at what cost? Here’s how to calculate how much it will cost to have a kit in your home.

Why use a roof defroster?

If you live in a place where there is no significant accumulation of snow (or snow at all!), then you are most likely unfamiliar with roof de-icing kits.

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

A roof defroster cord is an electrical cord that looks a lot like an extension cord. Except the purpose of the defrost wire is not 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, much like the wires in a toaster or electric heater. .

Attach the wire to your roof in a looping W pattern for the first few feet above your eaves (as well as down your downspouts). When when the snow comes, you turn it on. The wire heats up and melts the snow, blowing it off the eaves.

The purpose is not cosmetic, most people love the cozy look of snow covered roofs, but to protect both the roof, the internal structure of the house and the occupants of the house.

Snow accumulation at the edge of the roofline can lead to “ice dams,” where the difference in heat between the warm roof and the cold eave causes melt runoff to freeze right at the edge. That can not only result in large chunks of ice breaking off and falling off the roof (causing significant property damage and personal injury in the process), but it can also damage the roof.

As the meltwater reaches the edge and freezes, it can lift the shingles and roof membrane. Water can then flow freely under ceiling materials and even into the wall cavity, leading to drywall damage, structural damage, and mold.

To avoid these problems, some people use roof rakes to remove snow from their roofs after heavy snowfalls, hoping that the sun will warm the roof and finish removing snow and ice. But depending on the area you live in, the solar orientation of your roof, the amount of snow falling, and the design and level of insulation of your roof, a roof rake may not be practical or effective.

How much does it cost to run a roof defroster?

If you think it can’t be cheap to use a giant electrical cable to melt snow off your roof in the freezing depths of winter, you’d be right. A significant amount of energy is required to melt snow and ice, but it might not be as bad as you imagine depending on how often you need to use the system.

Let’s run through a basic estimate, and you can tailor our estimate using our formulas to fit the size of your home, the area you need to defrost, and local electricity costs.

How to estimate the amount of anti-icing cable you need

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

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

You should also be aware of downspouts, as there is no use melting the water on your roof only to have it freeze in the downspout and be carried away from your house. At a minimum, you’ll need at least as many feet as the downspout, but many people double the wire to ensure there’s enough heat for it to flow freely (especially if the downspout leads to a buried drain under the garden).

If you want to plan a de-icing system with more precision than just a rough estimate, we recommend that you consult 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 you have 100 feet of roof with a 1 foot overhang (so you’ll need 100 feet * 2.8, or 280 feet for just the eaves). Add four downspouts that are 12 feet above 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 apply cable only to the part 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 entire edge of the roof all the way around the house to just the part out the back door that gets very little sun in the winter.

Calculation of the cost of laying de-icing cables

Now that we have a rough idea of ​​how much wire we are going to use in our theoretical house, we can consider how much power it will use.

Depending on the brand and thickness of the cables, de-icing cables use about 5 to 8 W of power per foot of cable. Note that power consumption is based on the physical length of the cable, not the length of the ceiling edge that cable runs through. For the sake of our calculations, let’s use 5 W because that’s what the almost ubiquitous Frost King cables use.

To calculate how much total power our cable run will use, we simply multiply the number of feet (in this case, 352) by the power per foot (5W) to arrive at a total load of 1760W.

Now that we know the wattage, we can use the same methods described in our guide to measuring your energy use to calculate how much the defrost system will cost per hour of operation.

First, we need to convert the operating load of 1760 W to kilowatt hours because that is how your electric company bills you. So we’ll multiply the charge by hours and divide by 1000 to convert.

(1,760W * 1 Hour)/1000  = 1.76 kWh

We then multiply that value by what we pay per kWh. According to the most recently released statistics from the US Energy Information Administration (using data through August 2022), the average cost per kWh in the US is 15.95 cents, so we will use that in our equation.

1.76 kWh * 0.1595 = 0.28

Our defrost 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 somewhere Day after tomorrow Frozen post-apocalyptic hell that requires you to run your meltdown cables day and night. It would cost you $6.74 per day and $202.12 per month to defrost your roof with our theoretical 1,760W system.

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

And if, say, a lot of snow fell but it was interspersed with long periods of sun that allowed you to run your defroster through the blizzard but left it idle, you’d spend a lot less. If you could get by with just 12 hours of runtime, your cost for any given month would be $13.47.