Best Heat Tape for Pipes: Length, Watts per Foot and Cost to Run

Total watts are watts per foot times length. The 6 ft Frost King is 42 W, the 12 ft Frost King 84 W, the 30 ft HEATIT 90 W and the 30 ft VEVOR 150 W. At 17.3 cents per kWh that is 0.73, 1.45, 1.56 and 2.60 cents an hour while the cable is heating.

The thermostat is what keeps the bill small. A cable that runs around the clock for 30 days costs $5.23, $10.46, $11.21 and $18.68 for those four. In practice the cable only runs when the pipe or air is near freezing. If it runs 12 hours a day for 30 days, cut those numbers in half. Self-regulating cable also draws less than its rated watts once the pipe warms, so its rated figure is a ceiling.

Higher rates scale it up. A 90 W cable running nonstop for a month costs $7.65 in North Dakota at 11.81 cents per kWh and $19.04 in Connecticut at 29.38 cents. Compared with the cost of a burst pipe, any of these is small, which is why the thermostat and a few feet of insulation over the cable matter more than squeezing out watts.

Constant wattage cable puts out the same heat everywhere, all the time it is on. The Frost King kits are fixed length with a thermostat that switches them on and off. With constant wattage cable, the standard rule is never to let it cross or overlap itself, since the overlap can overheat. Check the instructions that come with it.

Self-regulating cable, like the HEATIT and VEVOR, has a core that lowers its own output as it warms up, foot by foot. A cold section gets more heat and a warm section less. That makes it more forgiving and a little cheaper to run, and it is what most people should buy for longer runs. Both still need to match the length of pipe you are protecting, so measure first.

Whatever you buy, check that the cable is listed for your pipe material. All the cables here are sold for metal and plastic pipe. Use a cable with a listing mark such as UL or ETL where you can. Wrap pipe insulation over the cable unless the instructions say not to, because it holds the heat on the pipe instead of losing it to the cold air.

If your cable has no thermostat, or you run a heat lamp or small heater in a pump house, a thermostatic outlet adds one. The Thermo Cube TC-3 switches its two outlets on at about 35 F and off above 45 F air temperature. It reads the air, not the pipe, so it is a backstop, not a replacement for a cable with its own thermostat.

Heat tape protects one pipe. It does nothing if a different pipe freezes, if the power goes out or if the cable fails. A few battery leak sensors under sinks, by the water heater and in the crawl space tell you when water is where it should not be, and a shutoff valve can close the main on its own. Our guide to whether a water leak shutoff valve is worth it covers both.