The higher is the efficiency of a fuel , the more is the amount of energy used for work and hence more is the energy produced for operating any equipment or device.
For example if we use the best quality of coal i.e anthracite , the efficiency of energy production from this coal will be much higher as compared to the efficiency of energy production of a low grade coal. The quantity of fuel used also depend on the efficiency of fuel. A high efficiency fuel is required in less quantity as compared to a low efficiency fuel.
