Lloyd Mandeno was born on 3 October 1888 at Rangiaowhia, near Te Awamutu, the son of farmer William Henry Mandeno and his wife, Mary Graham Snodgrass. After boarding at St John’s Collegiate School, Auckland, he enrolled at Auckland University College in 1905. The following year he transferred to Canterbury College, where he studied for a bachelor of engineering (electrical); he graduated in 1912. His involvement with electric-power generation began in 1910–11 with the installation of the first alternating-current plant in Auckland, a 6,600-volt link between tramways. His knowledge was further extended by working at the Horahora hydroelectric station, built by the Waihi Gold-Mining Company. On 18 June 1913 he married Constance Mary Woodward at Mangere; they were to have three sons.
A passionate advocate of hydroelectricity, Mandeno worked for the Tauranga Borough Council from 1915 to 1926, promoting the use of electricity from the Omanawa Falls power station. A local gasworks had been set up in 1909, and he had to combat residents’ reluctance to change to another unknown method of cooking. He set up a shop in Devonport Road as a demonstration room, generating electricity with a dynamo driven by an oil engine; within a year 100 installations had been made. He then persuaded R. S. Ready to build a new home without a chimney, relying solely on electricity. To provide hot water he designed a galvanised-iron cylinder, insulated with six inches of pumice, with a 350-watt heating element. It was possibly the world’s first electric storage heater, and the house was said to have been the first in the world dependent on a public power supply for all its energy requirements.
In the early 1920s Mandeno wrote a paper on electricity demand in Tauranga, especially that used for cooking. At the time the town was the most advanced consumer of electricity for domestic purposes in New Zealand: there were no electric ranges in service in Auckland, and few in Christchurch and Dunedin, whereas 10 per cent of Tauranga residents were using them. Mandeno later improved on the original water heater, using copper to prevent corrosion and developing a quick recovery system for heating water after heavy use. He patented the idea, but lacked the business skills to profit financially.
Mandeno faced two major obstacles when he began planning a second power station for Tauranga. The government initially refused a licence because of its commitment to the Arapuni scheme, and ratepayers had to approve a sizeable loan. Cabinet Minister William Herries’s intervention obtained the licence in 1922 and Mandeno’s oratory won over the residents. When Whakatane and Opotiki declined to buy excess power, he persuaded the Auckland Electric Power Board to take the surplus.
In 1925 Tauranga became the first electric-power authority in the world to use the single-wire earth-return system of line construction, known as ‘Mandeno’s clothesline’, which made it economically viable to reticulate remote and sparsely populated areas. This system was used in Northland during the late 1930s, in the central North Island after the Second World War, and subsequently in Australia, South America, South Africa, India and the Soviet Union. Mandeno later modified it to prevent interference on telegraph lines.
When Mandeno’s involvement in the establishment of the Tauranga Electric Power Board caused Tauranga’s mayor, Bradshaw Dive, to accuse him of a conflict of interest, he left and set up a private practice in Auckland in 1926. From around this time, however, he began to suffer from ill health. For five years from 1929 he lived largely on liquid food, and his weight dropped by three stone. Nevertheless, during the early 1930s he worked on several mining projects in the South Island, including the damming of the Shotover River for gold recovery, an alluvial mining venture in Moonlight River gorge and a report on a tungsten mine at Glenorchy. He was also involved with the Kerikeri hydroelectric scheme (1930–31), the Onekaka Iron and Steel Company’s electrification and the formation of the Bay of Islands Electric Power District in 1937.
Mandeno was responsible for many innovations: he developed portable moulds to cast concrete poles on site, experimented with prefabricated steel poles in 1921, and used New Zealand’s first pole-erecting machine at Kaikohe. He laid a submarine cable – one of the first of any length in the country – to Zane Grey’s fishing camp on Urupukapuka Island in the Bay of Islands, and set up the first electrically powered sawmill and milking shed in the North Island. He also provided power for Chateau Tongariro and chair-lifts to ski fields, and developed a high-pressure hot-water system for Auckland and Tauranga hospitals. The Kuratau hydro station near Lake Taupo, which opened in 1962, exemplified his inventiveness and tenacity. When a rocky gorge proved unstable he designed a new rock-fill dam, and in a race against the waters of the rapidly filling hydroelectric lake, supervised its construction himself when contractors refused to tender.
He served on the One Tree Hill Borough Council from 1931 to 1956, and was deputy mayor from 1944 to 1956. He was made an OBE in 1965. At the end of his career he had nine hydro stations to his credit, including the Lloyd Mandeno Power Station in the Kaimai Range, which was opened by Prime Minister J. R. Marshall on 2 September 1972. An unorthodox figure, he made an enormous contribution to electric-power generation in New Zealand. As he himself said, ‘I am by nature too prone to seek out a path not regularly trodden by others’. Constance Mandeno died on 18 October 1970, and Lloyd died at his home in Auckland on 30 December 1973; he was survived by his sons.