472 



Report S.A.A. Advancement of Science. 



usually started with less generators to allow for increased demands 

 without involving an undue number of generators later. 



In estimating the cost of generating and distributing electric 

 energy for any given case, one may calculate capital outlay, fuel and 

 labour charges very closely, but the load factor and diversity factor, 

 which have such an important influence on the working cost per unit 

 and on the capital outlay respectively, can only be more or less 

 closely approximated, according to the experience and judgment of 

 the estimating engineer. 



Effect of Load Factor. 



In England the load factor for lighting alone during 1905 was 

 in one case as low as 5.75 per cent. There are 12 undertakings 

 having load factors below 8 per cent., and 37 below 10 per cent. 

 The average is about 15 per cent. 



Stations which generate electric energy for both tramways and 

 lighting have load factors usually between 20 per cent, and 25 per 

 cent., but Salford has a load factor of 28.55 per cent., and South 

 London 29.32 per cent. None reach 30 per cent. 



A station supplying tramways only may have a load factor as 

 high as 52 per cent, to 53 per cent., but the author is not aware of 

 any public electric supply stations with a loadi factor as high as 

 60 per cent. 



The effect of the load factor on the total cost of supply, 

 including interest on capital, is shown by the following Table A. : — 



Table A. 



Shewing the effect of " load factor " on the cost of Electric 

 energy supplied from a Public Supply Station. 



