What is Dimensional Formula of Efficiency ?

Efficiency can be  defined as the  ratio of useful output energy to the amount of input energy.

Mathematically,

Efficiency = Useful output energy / Input energy.

Dimensional formula of output energy = M¹L²T^-2
Dimensional formula of input energy = M¹L²T^-2

Putting these values in above equation we get,

Dimensional formula of Efficiency = M⁰L⁰T⁰.
Efficiency has no SI Unit. (As both values are of energy).