The importance of the Kiel Canal was also militaristic. At the time of Imperial Germany's naval arms rivalry with Great Britain it was strategically much easier and safer to transport the ships to and from the Baltic via Kiel to the base at Wilhelmshaven than it would be going around Denmark into the North Sea
Apparently it can save up to 20 hours (it's also apparently the most used canal in the world).
Naval and security concerns were the main rationale for constructing the canal in the nineteenth century. The Kiel Canal would easily allow the transfer of German naval power from the Baltic to the North Sea, or vice-versa. This gave the Kriegsmarine a degree of flexibility in its naval planning as it did not have to maintain two separate battlefleets in both bodies of water. Although transitioning across Denmark might not eat up time in peace, during war the time saved via the canal would greatly help German planning.One of the big fears in German naval circles in the 1890s was that the French (or the British) fleets would link up with the Russian fleet and that maintaining two separate fleets would lead to a dissipation of German naval power. Moreover, the neutrality of Denmark in war could not be guaranteed and the fear was that it would aid in this conjunction of Entente naval power. The German General Staff was very reluctant to plan for an invasion of Denmark as it took away vital manpower for what was essentially a naval mission. Therefore, the Kiel Canal represented a solution to both of these problems.