That is what I have in my shed. It doesn't work because the water freezes to the coils. Once this starts it keeps getting worse until you thaw the coils. Sure if you live where the temperature is never below freezing they are an option, but when the temperature gets colder they are not an option.
Not to mention I need heat to keep my plumbing from freezing.
Not to mention I need heat to keep my plumbing from freezing.