 Vanguard was designed to carry 4 @,@ 850 long tons of fuel oil and 427 long tons ( 434 t ) of diesel fuel . With a clean bottom , she could steam at a speed of 15 knots ( 28 km / h ; 17 mph ) for 8 @,@ 250 nautical miles ( 15 @,@ 280 km ; 9 @,@ 490 mi ) . The ship had four 480 @-@ kilowatt ( 640 hp ) turbogenerators and four 450 @-@ kilowatt ( 600 hp ) diesel generators that supplied the common ring main at 220 volts . Their total output of 3 @,@ 720 kilowatts ( 4 @,@ 990 hp ) was the largest of any British battleship . 
