 The ships'company is 679 rising to 1,600 with air element added. A more recent parliamentary reply stated the average crew size will be 672. They will have a displacement of 65,000 tonnes on delivery, but the design allows for this to reach over 70,000 tonnes as the ship is upgraded through its lifetime. They have an overall length of 280 metres (920 ft), a width at deck level of 70 metres (230 ft), a height of 56 metres (184 ft), a draught of 11 metres (36 ft) and a range of 10,000 nautical miles (12,000 mi; 19,000 km). The Ministry of Defence decided not to use nuclear propulsion due to its high cost, so power is supplied by two Rolls-Royce Marine Trent MT30 36 MW (48,000 hp) gas turbine generator units and four Wärtsilä diesel generator sets (two 9 MW or 12,000 hp and two 11 MW or 15,000 hp sets). The Trents and diesels are the largest ever supplied to the Royal Navy, and together they feed the low-voltage electrical systems as well as four GE Power Conversion's 20 MW Advanced Induction Motor (arranged in tandem) electric propulsion motors that drive the twin fixed-pitch propellers.
