\usepackage{} -- textcomp & \celsius vs. {\textcelsius}

So far the only way I've found to properly insert ˚C is to

\usepackage{textcomp}

...

{\textcelsius} % Note this won't work in math mode.  No different spacing is needed around this.

_____________

{\celsius} % Does not work.
\celsius % Does not work, even in math mode.
\textcelsius % Does not work.

I had previously found an online forum that suggested using $^{\circ}$C every time, but that's tedious, ONLY works in math mode, and had caused some errors.