RV Tank Heaters: What They Draw, and When They're Worth It

If you camp when nights drop below freezing, sooner or later you'll wonder whether your tanks will freeze. Tank heaters are one answer.

01What they are

Tank heaters are thin electric pads stuck to the outside bottom of your fresh, grey and black tanks. Most turn on by themselves when the tank gets near freezing, usually somewhere around 40°F at the pad, and turn off as it warms.

Many newer rigs come with them. You can add them to older rigs.

02How much power they use

Most pads run on 12 volts. Each pad typically draws a few amps when it's on. With three or four tanks, that adds up:

• 3 pads × about 4 amps each = about 12 amps when all are on
• That's roughly 140 to 150 watts

They don't run all the time; they cycle with the temperature. But on a cold night, they can run a lot. On a small battery, without shore power or a generator, they can drain it overnight.

On shore power, your converter supplies the 12 volts, so it's not a concern.

03When they're worth it

• Overnight lows in the 20s or colder for more than one night
• Camping on shore power or with a big battery bank
• Tanks that hang below the floor with no heated, enclosed underbelly

04When they're not enough

Tank heaters protect the tanks, not the pipes, valves and hoses. Exposed valves and the outside water hose freeze first. See keep water from freezing at camp.

05Other ways to protect tanks

• Keep a little liquid in the grey and black tanks so the pads have something to warm, but don't fill them up.
• Run the furnace. On rigs with a heated underbelly, furnace ducts warm the tank area.
• Skirting around the bottom of the rig holds heat.
• Dump before a hard freeze, then add a little RV antifreeze to the tanks.

06Don't forget the switch

Most tank heaters have a switch inside the rig. Turn it on before the cold night, and off when you leave. Pads running against an empty tank waste power.

Photo: RV Sewer Dump Valve by Dave Bezaire, BY-SA 2.0.

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