Queen Elizabeth's boiler and turbine combinations

The historical class is 196.2 metres long and 28 metres in beam. Queen Elizabeth, Valiant and Malaya use twenty-four Babcock and Wilcox boilers, while Warspite and Barham use twenty-four Yarrow boilers. Their nominal pressure is 235 psi, with six boilers in each of four rooms. British battleships commonly use this arrangement, while battlecruisers favour eight boilers per room and may have five rooms. SS Imperator uses the same Yarrow boiler type rated at 265 psi. Queen Elizabeth, Warspite and Malaya have the more efficient Parsons turbine sets, with cruising units for improved fuel economy; Barham and Valiant have Brown-Curtis sets. The intended output is 75,000 shaft horsepower, giving a rough comparison above 3,000 horsepower per boiler. Barham is the slowest example, producing less than 71,000 shaft horsepower at deep load and reaching 23.9 knots on trials, against a class average near 24 knots.