A unit of this size is quite capable of powering the average home. A fuel cell converts the chemical energy of a fuel into electrochemical energy. This conversion is direct, without any intervening thermal or mechanical steps. Consequently, the efficiency of a fuel cell is not limited by the same laws that limit the efficiency of conventional technologies such as internal combustion engines, steam engines, or turbines.
Fuel cells are very much like batteries.
However, the single cell is quite small and can be connected together in series to give higher voltages, or connected in parallel to give higher current. In practice, the cells are connected in a combination of series and parallel to give both useful current and useful voltage. A battery is a 'closed' system with all its chemical energy stored within its case. A fuel cell is an 'open' system that stores negligible chemical energy within its structure but is fuelled from an exterior source. While the fuel cell is supplied with fuel, it will never run 'flat' like a battery.