[Tex/LaTex] Subfigures one below the other

Question

I have three figures of width=4.0in and height=2.0in. There is a legend "south outside" of the figures. Anyways, I want to have all three figures on one page. If it's not possible, since they are too big, two figures on one page and the other on the next. However, when I simply include the graphics (code is provided at the end), then there is only one figure per page. And the rest of the page gets filled with text – which I don't want. I was thinking, maybe the subfigures environment would work? – But can subfigures be one below the other? Or are they always parallel?

\begin{figure}[t]
\centering
\input{power1}
\caption{Input power.}
\end{figure}
\begin{figure}[t]
\centering
\input{power2}
\caption{Output power}
\end{figure}
\begin{figure}[t]
\centering
\input{average}
\caption{Average}
\end{figure}

Answer 1

Experiments with [p!t] placed all three on the same page, but only if they were inserted at the top of the page. If one or two will fit on the current page, then they will be and the rest will follow ASAP.

\documentclass{article}
\usepackage{afterpage}
\usepackage{lipsum}

\begin{document}
\lipsum[1-2]
\afterpage{% delay insertion to the top of the next page
\begin{figure}[p!t]
\centering
\rule{4in}{2in}
\caption{Input power.}
\end{figure}
\begin{figure}[p!t]
\centering
\rule{4in}{2in}
\caption{Output power}
\end{figure}
\begin{figure}[p!t]
\centering
\rule{4in}{2in}
\caption{Average}
\end{figure}%
}% end of \afterpage
\lipsum[3-8]
\end{document}