They had a length overall of 180 feet (55 m) and a beam of 22 feet 8.5 inches (6.922 m), and were powered by two 800 horsepower (600 kW) Vickers eight-cylinder two-stroke diesel engines and two 420 horsepower (310 kW) electric motors.

Group 1 boats were not fitted with a deck gun during construction, but those involved in the Dardanelles campaign had guns mounted forward of the conning tower while at Malta Dockyard.

[1] E-Class submarines had wireless systems with 1 kilowatt (1.3 hp) power ratings; in some submarines, these were later upgraded to 3 kilowatts (4.0 hp) systems by removing a midship torpedo tube.

[3] When war was declared with Germany on 5 August 1914, E2 was based at Harwich, in the 8th Submarine Flotilla of the Home Fleets.

[4] On 14 August 1915, E2 sank Turkish minelayer Samsun with her two officers and eight crew near Erdek.