I've got the advice to use \thead
in order to force a line break within the table header. That works perfectly but the distance to the toprule and midrule increased. It's a small difference I know but it decides whether the whole table fits on the page or not...here is my MWE of a table with \thead
and one without. I removed the linebreaks for the example.
\documentclass{scrreprt}
\usepackage{microtype}
\usepackage[sc]{mathpazo}
\usepackage{xfrac}
\usepackage{booktabs}
\usepackage{tabularx}
\usepackage{caption}
\usepackage{siunitx}
\usepackage{makecell}
\renewcommand\theadfont{\bfseries}
\usepackage{lipsum}
\begin{document}
\lipsum[2]
\begin{table}[htbp]
\caption[Uebersicht aller PV-Anlagen im Testnetz \textit{Uniwohngebiet}]{Uebersicht aller PV-Anlagen im Testnetz \textit{Uniwohngebiet}}
\label{tab:Uebersicht_PV}
\small
\centering
\sisetup{output-decimal-marker = {.}}
\begin{tabular*}{\textwidth}{@{}l @{\extracolsep{\fill}} S @{\extracolsep{\fill}} c @{\extracolsep{\fill}} c @{\extracolsep{\fill}} c @{}}
\toprule
{\thead{column-1}} & {\thead{column-2}} & {\thead{column-3}} & {\thead{column-4}} & {\thead{column-5}}\\
\midrule
VNBE014220 & 3.69 & 16 & 1 & x\\
VNBE014469 & 11.47 & 16 & 1 & \\
VNBE015412 & 3.51 & 16 & 1 & x\\
\bottomrule
\end{tabular*}
\end{table}
\lipsum[11]
\begin{table}[htbp]
\caption[Uebersicht aller PV-Anlagen im Testnetz \textit{Uniwohngebiet}]{Uebersicht aller PV-Anlagen im Testnetz \textit{Uniwohngebiet}}
\label{tab:Uebersicht_PV}
\small
\centering
\sisetup{output-decimal-marker = {.}}
\begin{tabular*}{\textwidth}{@{}l @{\extracolsep{\fill}} S @{\extracolsep{\fill}} c @{\extracolsep{\fill}} c @{\extracolsep{\fill}} c @{}}
\toprule
{\textbf{column-1}} & {\textbf{column-2}} & {\textbf{column-3}} & {\textbf{column-4}} & {\textbf{column-5}}\\
\midrule
VNBE014220 & 3.69 & 16 & 1 & x\\
VNBE014469 & 11.47 & 16 & 1 & \\
VNBE015412 & 3.51 & 16 & 1 & x\\
\bottomrule
\end{tabular*}
\end{table}
\end{document}