The more effective argument in favour of hydroelectricity was that it would improve the efficiency of factories. Hydro was less expensive than steam power and allowed industry to replace large and cumbersome steam engines with small, compact, electric motors requiring only an electrical outlet at their place of operation. In contrast, steam-run machines required a maze of belts and shafts. Workers, the majority are women, are shown routing powder grooves at a Ministry of Defence factory.
