  Single crystal X-ray diffraction measurements were performed on
one-dimensional mixed valence vanadium bronze $\beta$-SrV$_6$O$_{15}$ in which
a metal-insulator transition exists at 170 K. Above 170 K the P2$_1$/a
structure with zigzag order of Sr in the tunnels of vanadium is confirmed. In
the structure below 170 K, the P2$_1$/a space group is retained with a b-axis
threefold increase and a charge order appears. A Bond Valence Sum analysis
shows that the charge order may consist in clusters of V$^{4+}$ regularly
spaced along 1D direction.
