The "Formidable"-class ships were powered by a pair of 3-cylinder triple-expansion engines that drove two inward-turning screws, with steam provided by twenty Belleville boilers. The boilers were divided into three boiler rooms and were trunked into two funnels located amidships. The boilers proved to be troublesome in service, with all three members of the class experiencing problems with them, particularly as the ships aged, between 1909 and 1914. The "Formidable"-class ships were rated for a top speed of from . The ships' normally carried of coal for the boilers, but had a total capacity of , which provided a cruising range of at a cruising speed of .