Dear Eartha, I have deicing cable on my roof. I need it to prevent roof leaks, but is there any way to dial back the energy use?
Roof deicing cable, also known as heat trace or heat tape, is a common solution to the fearsome ice dams we see on our roofs each winter in Summit County. Ice dams occur when snow on your roof melts then refreezes at the colder eaves, creating a barrier that traps water. This trapped water can lead to roof leaks and water damage. Using electricity to heat up and create channels for the melt water to run through, heat trace is a practical yet energy intensive way to mitigate the ice buildup. But is there a good way to minimize its impact on both our wallets and the planet?
The Cost of Heat Trace
Why should we concern ourselves with running heat tape efficiently? Those who have it know the painful impact heat trace has on wintertime energy bills. But to nail down the true financial and environmental cost of heat trace, we need to look at the numbers.
The main factors that affect how much energy a system uses are the length of cable, the amount of power used per foot, and the amount of time the heat trace is on. Since deicing cable typically zig-zags across the edge of the roof, the length measurement adds up fast. A 40-foot stretch of roof will likely have about 100 linear feet of heat trace. And that doesn’t account for gutters and downspouts.
Most modern heat trace products use about 8 watts of electricity per linear foot. So, if you have 100 linear feet of heat tape on the roof, it will use 800 watts of electricity when running. Put into perspective, that’s equivalent to 80 LED light bulbs.
Many local heat tape systems are turned on and off seasonally, say November 1st to May 1st. Without additional timers in place, these deicing systems are running 24 hours a day for 181 days annually. Can you imagine leaving those 80 lightbulbs on 24/7 for six months?
Now, let’s do the utility bill math. Remember that 100 linear feet of 8-watt heat tape uses 800 watts of electricity when running. We pay for electricity in kilowatt hours, so 800 watts running 24 hours per day for 181 days equals 3,475 kilowatt hours. At a rate of $0.13 per kilowatt hour, that’s over $450 a year. Yowzah!
While our electricity is increasingly generated by renewables, there is still a hefty environmental impact associated with energy usage. Considering today’s grid, that amount of electricity emits 1.5 metric tons of carbon dioxide into the atmosphere every year. It’s also half the amount of electricity used by the average Summit County home each year – just for heat trace. I don’t know about you, but I’m convinced this is worth doing something about.
What We Can Do
For starters, spring has sprung in the mountains, and it’s time to find the switch to your heat tape and turn it off for the season. It’s also a great time to come up with a plan for using the heat tape more efficiently next year.
The single most impactful way to reduce the energy consumption of heat tape is to put a timer on the circuit. The ideal time to melt ice on the roof is during the day, when warmer temperatures and the sun provide extra melting power. During cold winter nights, these systems just aren’t effective, thus working hard to do very little. Simply putting your heat trace on a timer to only run from 6am – 6pm can save 60% on electricity usage and cost compared to running it seasonally 24/7. Even more sophisticated controls exist that use weather conditions, moisture sensing, and even smart cameras to fine tune heat tape usage that might get you another 20-25% in savings. These solutions still require careful monitoring and should only be installed by a licensed electrician. Some experts can even remotely manage your system for you!
Heat trace helps protect our buildings from hazardous ice dams, and in some cases it’s unavoidable. But it has a major impact on the planet and our wallets. If everyone took greater control of these energy intensive cables, imagine the impact that would have!
Ask Eartha Steward is written by the staff at the High Country Conservation Center, a nonprofit dedicated to waste reduction and resource conservation. Submit questions to Eartha at info@highcountryconservation.org