Gutter Heat Cables and De-Icing in St. Louis: Worth It or Not?
Every November somebody in the county asks whether heat cables are the answer to the icicles along the north eave. Sometimes they are. Often they're a $600 way of not fixing a $200 problem. Here is what they actually do, what they cost to put in and run in St. Louis, and where they make sense.
What a heat cable is
An electric heating cable, run in a zigzag along the roof edge and down inside the gutter and downspout, that keeps a channel of meltwater flowing so ice can't dam at the eave or freeze the downspout solid. It doesn't heat the roof; it keeps a path open.
There are two kinds, and the difference matters:
- Constant-wattage cable puts out the same heat whether it's 30 degrees or 10 below, and whether it's wet or dry. Cheap to buy, expensive to run, and it should be switched off manually when it isn't needed. This is the box-store product.
- Self-regulating cable changes its output with temperature along its length — more heat where it's cold and wet, almost none where it's dry. Costs two to three times more per foot, uses far less power over a winter, and can be left on a thermostat or a snow-and-moisture sensor.
For a roof in St. Louis that sees ice for a few weeks a year rather than a season, self-regulating with a sensor is the version that doesn't show up on the electric bill.
What it costs here
| Item | Typical St. Louis cost |
|---|---|
| Constant-wattage cable, DIY, per foot | $2 – $4 |
| Self-regulating cable, installed, per foot | $12 – $22 |
| Thermostat or snow/moisture controller | $100 – $350 |
| GFCI-protected outdoor circuit, by an electrician | $200 – $600 |
| Typical 60–80 ft eave and two downspouts, installed | $900 – $2,000 |
Running cost: a constant-wattage run of 80 feet at about 5 watts a foot is 400 watts, or roughly 10 kWh a day if left on. At Ameren Missouri residential rates that's a dollar and change a day, so $30–$40 a month for each month it's switched on. Self-regulating cable on a sensor for a typical St. Louis winter runs a fraction of that, usually under $15 for the season.
What it fixes and what it doesn't
Heat cable fixes the symptom: ice at the eave and in the downspout. It does not fix the cause, which on almost every St. Louis house with ice dams is heat escaping from the living space into the attic, warming the roof deck, melting snow that refreezes at the cold overhang. The cure for that is attic air sealing and insulation, and on a 1960s ranch in Florissant or Hazelwood with six inches of old batts, that's a better use of $2,000 than any cable.
Heat cable also does nothing for a gutter that's holding water because it lost its pitch. That water freezes with or without a warm roof. Reset the pitch first — winterizing gutters in St. Louis covers the checklist.
Where cable genuinely belongs
- North-facing eaves under a shaded roof where snow never melts from above and the gutter stays frozen for weeks.
- Roof valleys that dump onto a short gutter run, where meltwater concentrates and refreezes.
- Downspouts on the north side of a two-story that freeze solid and split at the elbow every winter.
- Low-slope porch roofs and dormers on older city homes, where the roof can't be insulated from below and the ice dam backs water under the shingles into the plaster.
- Homes where the attic can't be fixed — cathedral ceilings, finished attics in Kirkwood and Webster Groves with no space to add insulation.
On those houses a self-regulating cable is a reasonable, permanent fix. On a house with a cold, well-vented attic and a gutter that drains, it's a solution looking for a problem.
Installation notes
- The cable clips to the shingles in a zigzag, drops into the gutter, and runs the length of it, then loops down each downspout to the bottom. The gutter section is what keeps the outlet open.
- It must be on a GFCI-protected outdoor circuit. If there isn't one at the eave, an electrician adds it; a cable plugged into an extension cord through a window is a fire and shock risk.
- Cable goes on clean gutters. A run full of December oak leaves with a cable in it cooks the leaves and does nothing for the ice. Clean first.
- Guards and cable don't mix well. Micro-mesh over a cable works if the cable is inside the gutter under the mesh; reverse-curve guards and cable don't.
- Don't run cable over a roof that's about to be replaced. It gets torn off with the shingles.
Our honest position
We'll install cable where the list above applies, and we'll tell you when a $40 downspout extension and an attic contractor would serve you better. If the problem is a gutter that doesn't drain, that's a gutter repair and it's cheaper than the electrician. For what ice actually does to the metal once it forms, see ice, snow and gutters in St. Louis.
Need gutter work in St. Louis?
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