Hybridization of heavy machinery is in its early phase but it is likely to increase in coming years. This research presents a comparison of the energy efficiency of a conventional, hybrid-electric, and fuel cell hybrid powertrains in mobile work machines. The cost effectiveness of different powertrain technologies is also analyzed by lifecycle cost calculations for an underground mining loader. The comparison is based on the modeling and simulation work carried out in the Autonomie vehicle simulation software. The conventional powertrain model, diesel engine with a mechanical driveline, corresponds to an underground mining loader. The hybrid models have series hybrid powertrain and a battery pack as energy storage. For assuring equal comparison, all powertrain models have comparable operating performance. Simulations are carried out in a specific duty cycle which had been previously measured in a real mine. The simulation results show that the hybrid electric loader with a diesel engine has almost 30% better energy efficiency than the conventional loader whereas the fuel cell hybrid has more than 50% higher energy efficiency than the conventional loader. The lifecycle cost analysis indicate that the higher initial costs of the hybrid loaders are not that significant due to the high maintenance and ventilation costs in mining operation. Because of the low heat production and zero emission operation, a fuel cell hybrid loader can have a lot of potential to decrease the ventilation need and energy consumption of the ventilation in mining operation.