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Part IV: Solar Water HeatingChapter 6. Simple and Batch Water Heaters

Solar Stock-Tank and Livestock Water De-Icing

Using the sun to keep animal water from freezing, and the limits of a passive tank in deep cold.

Difficulty
Intermediate
Cost
$50–200
published

A stock tank freezes from the top and from the wind. The sun can load it with heat on a clear day. Insulation and a wind break can keep some of that heat until morning. That is the whole passive strategy, and it has a hard edge: a long cloudy stretch, a night well below zero, or a shallow tank in an open field will still ice over. Animals need water that day, not after the weather improves.

A photovoltaic panel wired to a heater only makes heat while the sun is up. The freeze you are fighting is often at night. A panel without a battery does not replace insulation, and it does not replace a backup that works in the dark.

This page is about livestock water. It is not a way to make drinking water for people, and it is not the batch heater. Do not plumb a stock tank into a house.

Difficulty

Level
Intermediate
Time
A weekend for a lid and a wind break, then a daily look all winter
Skills
Rough carpentry and the honesty to install a backup before the cold arrives

Cost estimate

$50–200

Foam, a dark south face, and an insulated lid with a drinking hole can land in the low end. A listed livestock tank heater on a proper circuit is the usual reason the cost reaches the high end. Buy the backup before you need it.

PieceTypical cost
Rigid foam and a protected cover$40–100
Dark panel or twinwall on the south side$20–60
Listed de-icer, if you add one$40–80

Materials

ItemQtyNotes
Existing stock tank1Deeper water changes temperature more slowly than a shallow pan. A tank animals can tip is the wrong tank.
Insulation for the north, west, east, and lidA few inchesRigid foam or a commercial insulated cover. Protect the foam from hooves and teeth.
Dark south face1Paint or a dark panel the animals cannot eat. No coating that is not safe if it ends up in the water.
Drinking opening1Small enough to limit heat loss, large enough for the animal, and checked daily so it has not iced shut.
Wind break1A fence, a bale wall, or siting below a rise. Wind strips more heat than a clear night does by itself.
Listed tank heater and a GFCI circuitThe backupInstalled for livestock, not a household heater on an extension cord. Hard-wired work belongs to an electrician.

Where the heat goes

Sun on a dark south wall or a dark bottom warms the water. An insulated lid cuts the long-wave loss to the sky and cuts the wind. A drinking hole is a deliberate leak in that lid. Make the hole serve the animal you actually have. A horse and a flock of birds do not share an opening size.

Glass is a poor lid. Animals break it, and broken glass in a watering tank is an injury. Use an opaque insulated cover or a plastic glazing that will not shatter into the water. Keep any glazing where a rubbing shoulder cannot fold it into the tank.

Earth helps. A tank set low, banked on the north, loses less than a tank on legs in the open. Do not bank so high that an animal, or a child, can fall in and have no way out. A frozen or partly frozen tank is a falling hazard. A ramp or a rough exit matters if anything can tumble in.

A stock tank that holds daytime heatThe south side is dark and sunny. The other sides and the lid are insulated. A small drinking hole stays open. Wind is blocked.WindInsulated lid and shaded sidesDrinkDaytime sun fills the tank with heat. Insulation has to carry that heat through the night.
South side dark and sunny, the rest insulated, a drinking hole left open, and the wind kept off the water.

The night the sun does not come back

Count the heat in daytime hours and the loss in nighttime hours. If today's sun did not warm the tank, tonight's insulation is only slowing the drop toward freezing. After two or three gray days, passive covers in a cold climate often lose. That is the weather, not a construction error.

Plan the backup while the tank is still liquid. A listed de-icer on a ground-fault protected circuit, sized for the tank and the climate, is the ordinary answer. Do not run a household extension cord across a wet yard and call it temporary all winter. A damaged cord near livestock water is a known way to kill animals. If the heater needs a new circuit, hire an electrician.

Check the opening every day in freezing weather. A lid that froze shut is not "still working." Animals go without water quickly in the cold, and a frozen tank is an emergency for them. Haul water or open the backup the same day. Do not wait for a better solar afternoon.

  1. Stop the wind and the top loss first

    Site the tank out of the prevailing wind, or build a break. Insulate the lid and the sides that do not face the winter sun. Leave a drinking hole.

  2. Give the sun a dark surface

    A south face that can absorb, protected from chewing. Skip window glass. If you glaze anything, use a plastic that fails without shards in the water.

  3. Install the dark-hours backup before the season

    A listed livestock de-icer on a GFCI-protected circuit, or a hauled-water plan you have already practiced. A solar panel alone does not heat the tank at night.

  4. Watch one cold clear night, then one cloudy stretch

    If the hole is iced over in the morning after a sunny day, you need more insulation or less wind, not a bigger story about the lid. If it ices after gray days, that is what the backup is for.

  5. Look every day

    Confirm liquid water and a way out of the tank. Remove a cover that is sagging into the water or a heater that has cracked.

Further reading

These links go to outside sources. This book cites them by link and does not copy their words or pictures.

General education, not a permit or a stamped design. Follow the safety note in the guide, read the safety disclaimer, and hire a licensed trade when the work requires one.