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APPENDIX D. ANNUAL KEPOKT OF CHIEF ELECTRICAL ENGINEER. The Chief Electrical Engineer to the Hon. Minister of Public Works. Sir, — I beg to report on the position of the electric-power developments of the Dominion for the past year as follows : — General Power Requirements. The general scheme of hydro-electric development for the Dominion as laid out by my predecessor is based on an estimated demand of one horse-power delivered to each five head of population. In estimating the generating-power required to deliver this amount an allowance is made to cover losses amounting to 23 per cent, of the power delivered. On the basis of the. 1916 census the following total power is thus required for the supply of the whole Dominion : — North Island. South Island. Total. Population .. .. .. ..650,000 450,000 1,100,000 Horse-power delivered .. .. 130,000 90,000 220,000 Horse-power generated .. .. 160,000 110,000 270,000 The 1921 census indicates an increase on these population figures of 14 per cent, for the North Island and 6J per cent, for the South Island, including all returned soldiers not included in the 1916 census. As the schemes already worked out in detail on the basis of the 1916 census allow a reasonable margin for development, it is not desirable to recast them at this stage, but the more rapid increase in the North Island than in the South Island must be taken into account. At the same time, the estimate of 0-2 h.p. per head of population must not be considered as an ultimate limit to the demand, which, owing to the favourable opportunities for cheap hydro-electric developments in the Dominion, will ultimately reach a much higher figure. Canada already has an installed capacity of 0-274 h.p. per head. California has an installed capacity of 0-53 h.p. per head, and it is estimated that by 1930 this will have been increased to 0-8 h.p. per head of population. The proposed hydro-electric developments in New Zealand are as economical as those in Canada, and generally more economical than most of those in California, and developments may therefore be anticipated here at least to the same capacity as in Canada. But in the meanwhile the basis of 0.2 h.p. per head is fairly ample, being approximately twice the power now used in Christchurch and Dunedin, which have been supplied with fairly cheap hydro-electric power for some years. Main North Island Scheme. In order to supply this power for the North Island a complete interconnected scheme was laid out by Mr. Parry, consisting of 1,112 miles of main transmission-lines and 309 miles of branch lines. For the main transmission-lines the distances and quantities of power to be transmitted involved the adoption of a pressure of 110,000 volts, and for the branches a pressure of 33,000 volts, except for the Waikato branch, where a pressure of 50,000 volts was already in operation from the Horahora power plant. This network is to be fed from three main points, viz. : — Proposed Ultimate Development. Capacity. Horse-power. Horse-power. Mangahao River .. .. .. .. ..24,000 24,000 Waikaremoana .. .. .. .. ..40,000 136,000 Arapuni .. .. .. .. .. .. 96,000 162,000 Totals .. .. .. .. 160,000 322,000 This system is to be connected up ultimately with the existing hydro-electric-power stations at Horahora (8,400 h.p.), New Plymouth (1,000 h.p.), and Wairua Falls (2,600 h.p.). The estimated cost of the whole North Island system, based on 12 per cent, excess over pre-war prices, was as follows :— Amount. Per Horse-power. Power-stations — £ £ Mangahao (24,000 h.p.) .. .. .. .. 438,654 18-30 Waikaremoana (40,000 h.p.) .. .. .. 544,369 18-16 Arapuni (96,000 h.p.) ... .. .. .. 1,078,700 10-80 Total power-stations (160,000 h.p.) .. .. .. 2,061,723 12-88 Main transmission-lines : 1,112 miles at £1,400 per mile .. 1,553,880 i Branch transmission-lines : 309 miles at £780 per mile .. 241,360) l Main substations .. .. .. .. .. 5-24 Distribution-lines and secondary substations .. .. 2,086,000 13-04 Interest during construction .. .. .. .. 271,271 1-69 Working capital .. .. .. .. .. 250,000 1-56 Totals .. .. .. .. £7,303,042 £45-63