Has it ever happened that one paper's findings were contradicted by another?
Make sure the difference comes from the experimentation not from the
adopted technique/method.
Make sure you have the same settings as the other paper. Sometimes
people make assumptions for the sake of simplicity in
experimentations. For example, I remember I did experimentation
assuming acyclic graph exists.
Do you have some kind of randomness (i.e. generating random
instances of the problem)? If yes, revise
its output. Sometimes you examine easy instances while others base
their experimentations on hard instances of the problem.
In some areas, there are benchmarks and robust solvers for particular
problems/structures. If your field have benchmarks, try to compare your method against it.


Either way, I am sure you have important parameters to control the experimentation (i.e. number of variables..etc). check their role.  

Most importantly, you need to theoretically justify why your method will save 14% while other method saves only 2% in practice.