52 The N.Z. Journal of Science and Technology. [Jan. 
states* that if the system of distribution of electric power were as fully 
developed in other industrial districts of Great Britain as in the north-east 
coast district the resultant economies in coal-consumption would amount 
in the near future to 25,000,000 tons of coal per annum. These economies, 
be it noted, are obtained as the result of burning coal under more economical 
conditions in a centralized power plant, the source of energy in the case 
cited being coal, and not head of water. If the value of the fuel saved be 
capitalized, and compared with the capital expended upon the power-supply 
system by the agency of which the saving is effected, we reach a startling 
conclusion. Assuming that the power is derived from water, the capital 
expenditure should not exceed £40 per horse-power of ultimate develop¬ 
ment under favourable circumstances, inclusive of generating plant, trans¬ 
forming plant, transmission-lines, and distribution-lines. Taking the saving 
in coal at 10 tons per horse-power per annum, and the average price 
at £1 per ton, the annual cost of coal is £10 per horse-power'—That is to 
say, the capital expenditure upon a hydro-electric power system is recover¬ 
able in four years by the saving in coal only, without reckoning upon any 
other economies and without taking any credit for increased production 
and other gains. Supposing we discount these figures somewhat, and reckon 
to recover the capital in five or even six years out of the coal saved, the 
conclusion is sufficiently striking to merit serious consideration. 
Economy in Operation and Maintenance. 
Coming next to the consideration of economies in operation and main¬ 
tenance due to centralization of the power plant, the saving in labour is 
considerable even where a fuel plant is used, if only by reason of the smaller 
quantity of coal required to be handled. As a matter of fact, however, 
the centralization of the power admits of the utilization of labour-saving 
devices in a remarkable degree. The greater the power plant the greater 
is the economy in labour, as it requires no more men to operate or control 
large units than small units, whilst in a water-power plant the number of 
men employed is less than one-third that employed in operating a fuel 
station of the same size. Take, again, the cost of maintenance, and compare 
the cost of maintaining a few large power-units of efficient type against 
the cost of a multiplicity of small units of an inferior type, and some idea 
may be formed of the saving effected. Over against this must, however, 
be set the cost of maintenance of transmission and distribution lines, 
substations, and management. It is quite evident, however, from what 
has been said that the net gain is considerable. 
Advantages to the Power-user. 
First, as regards the advantages of a bulk supply in general, the power- 
user is freed from the necessity of finding capital for a power-generating 
plant, including accommodation for a coal-store, and so he saves space 
which can be devoted to the purpose of his business. He is not restricted 
or hampered in the development of his business by the size of his power 
plant, but takes his supply of energy from the power-mains as he needs 
it, to suit the requirements of his business. He has not to maintain, a 
stock of coal, whilst the power usually costs him somewhat less than the 
* C. H. Merz, Electric-power Distribution. Paper read before the Newcastle 
meeting of the British Association, 1916. 
