Evan Parry was born on 30 November 1865 at Llanddeiniolen, Carnarvonshire, Wales, the son of William Parry, a slate quarry agent, and his wife, Eliza Williams. Evan was educated in Bangor and worked for a firm of marine engineers before moving to Glasgow University in 1890 to take a BSc degree in civil engineering and mechanics under Lord Kelvin. He was then employed as an engineer and manager at the Deptford power station, and at the British Thomson-Houston Company designing electrical machinery. In 1897 he became an assistant to H. F. Parshall, a consulting engineer involved in the electrification of tramways and railways and the formation of power companies. Parry was engaged in designing electrical equipment for the Central London Railway and for tramways in England, Scotland and Ireland.
In 1911 he was selected from an international field of applicants to be New Zealand's first electrical engineer in the Public Works Department. The government was about to embark on a large-scale programme of hydroelectric generation and Parry was charged with planning and designing the new system. His diverse experience and advanced ideas on voltage, frequency and systems ably fitted him for the task.
Parry had married Margaret Elizabeth Hughes at Llanberis, Wales, on 5 July 1895, and they arrived in New Zealand in July 1911 with their son, Evan. Parry began work in the same month, assisted by Lawrence Birks, who had prepared a landmark report in 1910 on the future demand for electricity. He was immediately immersed in the practical problems of constructing the Lake Coleridge station in the Southern Alps. This ambitious scheme would take water through a long tunnel to a powerhouse on the bank of the Rakaia River, with electricity being sent to Christchurch at an unprecedentedly high 66 kilovolts. Lake Coleridge was the experiment that would prove to the government whether large-scale state hydroelectric generation was feasible. The station was opened in 1914 and proved a great success, with the demand for electricity soon outstripping supply.
During the First World War Parry co-ordinated plans for harnessing various North Island water resources that would put New Zealand in the forefront of hydroelectric generation. His report to the minister of public works in 1918 provided the basis for more than two decades of development. Parry's scheme was for three stations, massive for that time, at Mangahao in the Tararua Range, Arapuni on the Waikato River, and Tuai below Lake Waikaremoana. These stations were to be linked by a network of 1,100 miles of 110-kilovolt transmission lines. The plan was to make power available to cities, industry and farms, and to every household however remote. Although the plan was ready by the end of the war, and many local organisations clamoured for the schemes to begin, a hiatus developed as the government baulked at making a start when labour was so scarce. A substantial loan had also to be raised.
In late 1918 Parry suddenly announced his intention to resign from the Public Works Department. His position had been upgraded to chief electrical engineer in 1913, and in spite of the government now virtually doubling his salary of £900 for a new five-year contract, he accepted an offer from the newly formed English Electric Company to be its chief engineer at £2,000 per annum. Parry's decision was perhaps also the result of frustration at the lack of progress and the politicisation of his plan. He had argued strongly that a non-political board be in charge of the construction process: this was not accepted by the government which, in line with well-established New Zealand tradition, kept the developments in the hands of the Public Works Department.
Under his successor, Lawrence Birks, Parry's plans soon came to fruition. By 1919 labour and money became available and construction commenced at Mangahao. With Gordon Coates as minister of public works in the 1920s, work also began at Arapuni and Tuai. The electricity from stations such as these would transform manufacturing, farming and domestic life in New Zealand.
Parry retained a keen interest in this country's electrical developments and corresponded regularly with his New Zealand colleagues. During a 1923 visit he advised on the conversion of Wellington's distribution system to take power from Mangahao. In England in 1924 he became a partner in Preece, Cardew and Rider, consulting engineers, and with them was associated in many electrical supply schemes in countries including India, Ceylon (Sri Lanka) and Australia. He was involved in the extensions to the coal-fired electrical generating plants at Evans Bay, Wellington, and King's Wharf, Auckland, and to the Waipori hydroelectric station serving Dunedin. Parry and his firm also acted as inspecting engineers for New Zealand government purchasing contracts.
Evan Parry was regarded as an outstanding teacher by younger engineers. He was a member of the Institution of Electrical Engineers and the Institution of Civil Engineers. He had an enormous library and was a voracious reader on many subjects, particularly those relating to ancient civilisations. He was also keenly interested in religion and in ecclesiastical architecture. Tall and slim, with grey eyes and black hair, Parry has been described as a 'real character and great fun to be with'. In London he and his wife entertained in style at their flat overlooking Regent's Park.
He visited New Zealand again in 1938. He died later that year on 17 December at Llandudno, Wales, survived by his wife and son. Parry is commemorated by the Institution of Professional Engineers New Zealand in the Evan Parry award. His son, Evan, returned to New Zealand in the 1920s and practised law in Wellington until his death in 1944.