Thermal efficiency analysis can be used to minimise the energy losses in laser welding. In the present study, laser welding and efficiency analysis are considered. The first and second law efficiencies for the welding process arc formulated and quantified for new parameters associated with the welding geometry. These parameters include excess mass ratio, loss mass ratio, and heat loss ratio. It is found that the first and second law efficiencies improve gradually with increasing excess mass ratio. However, the first and second law efficiencies reduce with increasing loss mass ratio and heat loss ratio, provided the decrease in efficiencies with increasing heat loss ratio is gradual.