I’ve had really good luck with this product.
I use it for battery thermal wrap
and diesel engine block heater.

Product description:

Plugs into a standard 15 amp electrical
outlet and turns power on automatically
according to outside air temperature.

Saves money by using power only
when temperatures require heating.

Two receptacles for use with
more than one electrical device.

Turns on at 20°F, off at 30°F.

Ideal for automotive applications,
including engine and battery heaters

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